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Abstract

Adults routinely make sense of others' actions by inferring the mental states that underlie these actions. Over the past two decades, developmental researchers have made significant advances in understanding the origins of this ability in infancy. This evidence indicates that when infants observe an agent act in a simple scene, they infer the agent's mental states and then use these mental states, together with a principle of rationality (and its corollaries of efficiency and consistency), to predict and interpret the agent's subsequent actions and to guide their own actions toward the agent. In this review, we first describe the initial demonstrations of infants' sensitivity to the efficiency and consistency principles. We then examine how infants identify novel entities as agents. Next, we summarize what is known about infants' ability to reason about agents' motivational, epistemic, and counterfactual states. Finally, we consider alternative interpretations of these findings and discuss the current controversy about the relation between implicit and explicit psychological reasoning. Expected final online publication date for the Annual Review of Psychology Volume 67 is January 03, 2016. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
PS67CH07-Baillargeon ARI 21 November 2015 14:39
Psychological Reasoning
in Infancy
Ren´
ee Baillargeon,1Rose M. Scott,2and Lin Bian1
1Department of Psychology, University of Illinois, Champaign, Illinois 61820;
email: rbaillar@illinois.edu, linbian2@illinois.edu
2Psychological Sciences, University of California, Merced, California 95343;
email: rscott@ucmerced.edu
Annu. Rev. Psychol. 2016. 67:159–86
First published online as a Review in Advance on
September 17, 2015
The Annual Review of Psychology is online at
psych.annualreviews.org
This article’s doi:
10.1146/annurev-psych-010213-115033
Copyright c
2016 by Annual Reviews.
All rights reserved
Keywords
infant cognition, psychological reasoning, theory of mind, rationality,
agency, mental states, false beliefs, implicit reasoning
Abstract
Adults routinely make sense of others’ actions by inferring the mental states
that underlie these actions. Over the past two decades, developmental re-
searchers have made significant advances in understanding the origins of this
ability in infancy. This evidence indicates that when infants observe an agent
act in a simple scene, they infer the agent’s mental states and then use these
mental states, together with a principle of rationality (and its corollaries of
efficiency and consistency), to predict and interpret the agent’s subsequent
actions and to guide their own actions toward the agent. In this review, we
first describe the initial demonstrations of infants’ sensitivity to the efficiency
and consistency principles. We then examine how infants identify novel en-
tities as agents. Next, we summarize what is known about infants’ ability
to reason about agents’ motivational, epistemic, and counterfactual states.
Finally, we consider alternative interpretations of these findings and dis-
cuss the current controversy about the relation between implicit and explicit
psychological reasoning.
159
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ANNUAL
REVIEWS
Further
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Contents
INTRODUCTION............................................................... 160
THERATIONALITY PRINCIPLE............................................... 161
Efciency...................................................................... 161
Consistency.................................................................... 162
ConsistencyTrumps Efciency.................................................. 162
IDENTIFYINGAGENTS........................................................ 162
InternalControl................................................................ 163
Self-PropelledObjects, Agents,andAnimals..................................... 164
PredictiveCues................................................................. 165
ATTRIBUTINGMOTIVATIONAL STATES.................................... 165
Goals.......................................................................... 165
Preferences..................................................................... 167
EmotionalStates ............................................................... 168
PredictingOthers Actions...................................................... 168
MakingSense ofIrrationalActions .............................................. 169
ATTRIBUTINGEPISTEMIC STATES.......................................... 170
Keeping Track of What Objects Agents Can See or Have Seen . . . . . . . . . . . . . . . . . . . 170
KeepingTrack ofWhatEvents AgentsHave Seen ............................... 171
Evaluating Irrational Agents: The Case of Epistemic Unreliability . . . . . . . . . . . . . . . . 172
ATTRIBUTINGCOUNTERFACTUAL STATES ............................... 173
Spontaneous-ResponseFalse-Belief Tasks....................................... 174
Elicited-InterventionFalse-Belief Tasks......................................... 176
HOW SHOULD EARLY PSYCHOLOGICAL REASONING
BECHARACTERIZED? ...................................................... 177
AlternativeInterpretations...................................................... 177
Implicit and Explicit Psychological Reasoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
CONCLUSION.................................................................. 179
INTRODUCTION
Over the past two decades, numerous reports have presented evidence that psychological reason-
ing, the ability to make sense of agents’ intentional actions, emerges early in infancy (0–2 years
of age). This evidence supports the mentalistic view that human infants are born equipped with
a psychological-reasoning system that provides them with a skeletal explanatory framework for
reasoning and learning about agents’ actions (e.g., Baillargeon et al. 2015, Baron-Cohen 1995,
Johnson 2005, Leslie 1994, Premack & Premack 1995, Scott et al. 2015b, Spelke & Kinzler 2007).
When infants observe an agent act in a simple scene, their psychological-reasoning system enables
them (a) to infer the mental states that underlie the agent’s actions and (b) to use these mental
states, together with a principle of rationality, to predict and interpret the agent’s subsequent
actions and to guide their own actions toward the agent. The rationality principle dictates that, all
other things being equal, agents will act rationally; corollaries of the principle include efficiency
(agents will expend as little effort as possible to achieve their goals) and consistency (agents will
act in a manner consistent with their mental states) (e.g., Baillargeon et al. 2015, Dennett 1987,
Gergely et al. 1995).
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In our review, we first describe the initial demonstrations of infants’ sensitivity to the efficiency
and consistency principles. We then examine how infants identify novel entities as agents. Next,
we summarize what is known about infants’ ability to reason about agents’ motivational states (e.g.,
goals and dispositions), epistemic states (e.g., knowledge and ignorance), and counterfactual states
(e.g., false beliefs and pretense). Finally, we consider alternative interpretations of these results and
discuss the current controversy about the relation between implicit and explicit psychological rea-
soning. In the limited space available, we could not include recent findings on infants’ sociomoral
reasoning (for reviews, see Baillargeon et al. 2014, 2015; Bloom 2013; Hamlin 2013). Neverthe-
less, it should be stressed that these findings provide additional support for those reviewed here:
Infants could not predict or evaluate social interactions among novel entities without first identi-
fying these entities as agents and determining what goals they are pursuing and what information
is available to them (e.g., Hamlin et al. 2007, Johnson et al. 2010, Meristo & Surian 2013, Sloane
et al. 2012). Our review highlights these foundational psychological-reasoning building blocks.
THE RATIONALITY PRINCIPLE
The initial investigations to address (implicitly or explicitly) infants’ sensitivity to the rationality
principle used the violation-of-expectation method, a prevalent looking-time method that takes
advantage of infants’ natural tendency to look longer at events that violate, as opposed to confirm,
their current expectations (e.g., Luo & Baillargeon 2005b, Stahl & Feigenson 2015, Wang et al.
2004).
Efficiency
The first demonstration that infants are sensitive to the efficiency principle came from experiments
by Gergely and Csibra using a novel detour task (e.g., Csibra 2008, Csibra et al. 2003, Gergely
et al. 1995). Infants ages 6 to 12 months first received familiarization trials in which an agent
had to move around or over an obstacle to reach a target. In the test trials, the obstacle was
removed, and the agent traveled to the target either in a straight line (new-path event) or along
the same detour path as before (old-path event). Infants looked reliably longer at the old-path than
at the new-path event, suggesting that they (a) attributed to the agent the goal of reaching the
target and (b) expected the agent to pursue this goal efficiently, in accordance with the efficiency
principle: With the obstacle removed, a more efficient path to the target became possible, and
infants detected a violation when the agent ignored this shorter path and followed the same path
as before. These conclusions were supported by a control condition identical to the experimental
condition except that in the familiarization trials the obstacle stood behind the agent and thus no
longer blocked access to the target; nevertheless, the agent used the same detour path as in the
experimental condition. Infants looked about equally at the two test events, suggesting that they
could not generate a rational explanation for the agent’s behavior in the familiarization trials (i.e.,
why did the agent detour en route to the target?), and they therefore held no expectation about
the agent’s actions in the test trials. These findings have been replicated in many laboratories (e.g.,
Brandone & Wellman 2009, Kamewari et al. 2005, Sodian et al. 2004).
Additional investigations indicated that infants expect efficiency not only in the length of the
path used to reach a target (they expect a shorter as opposed to a longer path), but also in the
number of actions performed to obtain an object (they expect a shorter as opposed to a longer
means-end action sequence; e.g., Scott & Baillargeon 2013, Southgate et al. 2008). Finally, infants
consider mental as well as physical effort in judging efficiency (Scott & Baillargeon 2013). In an
experiment with 16-month-olds, an agent saw an experimenter cover two identical toys with a
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transparent and an opaque cover (a small screen then hid the transparent cover from the infants,
so that neither toy was visible to them). Although both toys were physically equally accessible to
the agent, infants expected her to reach for the toy that was visible to her and hence mentally
more accessible. Together, these results indicate that infants’ understanding of efficiency is highly
abstract and encompasses both physical and mental effort.
Consistency
The first demonstration that infants are sensitive to the consistency principle came from experi-
ments by Woodward using a novel preference task (e.g., Woodward 1998, 1999). Infants ages 5 to
12 months first received familiarization trials in which an agent faced two different objects, object
A and object B; in each trial, the agent reached for and grasped object A. In the test trials, the
objects’ positions were switched, and the agent reached for either object A (old-object event) or
object B (new-object event). Infants looked reliably longer at the new-object than at the old-object
event, suggesting that they (a) attributed to the agent a preference or liking for object A, as the
agent always chose it over object B, and (b) expected the agent to continue acting on this preference
in the test trials, in accordance with the consistency principle. This finding has been replicated in
many laboratories (e.g., Luo & Baillargeon 2005a, Martin et al. 2012, Spaepen & Spelke 2007).
Subsequent investigations introduced two variations of the preference task that reinforced its
conclusions. In one variation, only object A was present in the familiarization trials; object B was
not added until the test trials (e.g., B´
ır ´
o et al. 2011, Luo & Baillargeon 2005a, Song et al. 2014).
Infants now looked equally at the two test events: Because no choice information was available in
the familiarization trials, infants had no basis for gauging the agent’s disposition toward object A
(i.e., did the agent reach for it because of a positive disposition toward it or because it was the only
object present?); as a result, infants could form no expectation about which object the agent would
choose in the test trials. The other variation was identical to the original preference task except
that new object C replaced object B in the test trials (e.g., L. Bian and R. Baillargeon, manuscript in
preparation; Robson & Kuhlmeier 2013). Infants looked longer at the new- than at the old-object
event, and this effect was eliminated when only object A was present in the familiarization trials.
Thus, when the agent repeatedly chose object A over object B, infants attributed to the agent an
enduring positive disposition toward object A, and they expected this disposition to be maintained
even in the presence of a new object.
Consistency Trumps Efficiency
When efficiency and consistency are pitted against one another, infants expect consistency to
prevail. After an agent demonstrates a preference for object A over object B in the familiarization
trials, infants expect the agent to reach for object A in the test trials even when physical constraints
are added so that a longer, more effortful means-end action sequence is required to retrieve it than
object B (Scott & Baillargeon 2013). Infants thus expect consistency to trump efficiency, at least
in situations where the effort required to obtain a preferred object is not much greater than that
required to obtain a nonpreferred object.
IDENTIFYING AGENTS
The findings summarized in the preceding section indicate that infants in the first year of life
are already capable of sophisticated psychological reasoning about agents’ actions. But whom do
infants view as agents? Do infants initially interpret the actions of only human agents and gradually
extend their action understanding to nonhuman agents? Or do infants reason from an early age
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about the actions of nonhuman agents? The available evidence supports the latter possibility:
Positive results have been obtained using nonhuman agents (e.g., boxes and geometric shapes)
with infants as young as 3 to 6 months (a) in detour, preference, and other psychological-reasoning
tasks (e.g., Csibra 2008, Luo 2011b, Schlottmann & Ray 2010) and (b) in sociomoral-reasoning
tasks (e.g., Hamlin et al. 2007, 2010, Hamlin & Wynn 2011). These findings naturally raise the
question of how infants identify novel nonhuman entities as agents.
Internal Control
One early hypothesis about how infants identify novel agents involved self-propulsion: Perhaps
any entity that can move on its own is viewed as agentive (e.g., Baron-Cohen 1995, Leslie 1994,
Premack 1990). In time, however, it became clear that this hypothesis was incorrect. Instead,
infants seem to identify a novel entity as an agent if it gives sufficient evidence that it has internal
control over its actions (i.e., that it chooses when and how to act). This evidence can come in a
variety of guises.
Detecting and responding purposely to changes. When a change occurs in a scene, a novel
entity is categorized as an agent if it gives evidence that it detects this change and responds to it
in a goal-directed manner (a goal-directed action is performed to achieve a particular outcome,
such as a communicative or an instrumental outcome). In a series of experiments, Johnson and
her colleagues ( Johnson et al. 2007b, Shimizu & Johnson 2004) tested 12-month-olds using a
preference task in which the “agent” was an oval entity covered with green fiberfill. When the
entity simply approached and rested against object A in the familiarization trials, infants did not
view the entity as agentive and looked equally at the new- and old-object test events (making clear
that self-propulsion alone does not constitute evidence of agency, nor does repeating a single,
fixed action that could be described as a goal-directed action). Positive results were obtained,
however, if the entity first interacted with an experimenter in a “conversation”: the experimenter
spoke in English and the entity responded with varying beeps. Because the entity gave evidence
that it detected and responded purposely to the experimenter’s utterances (as though pursuing
a communicative goal), infants perceived it as agentive. Additional results indicated that infants
did not view the entity as an agent if (a) the experimenter spoke but the entity remained silent
(suggesting that it was not merely seeing the experimenter talk to the entity that led infants to
view it as agentive) or (b) if the entity beeped but the experimenter remained silent (suggesting
that it was not merely observing the entity produce varying beeps that led infants to view it as
an agent; variable self-generated behavior, if it appears random, does not constitute evidence of
agency). In converging experiments using an attention-following task, Johnson et al. (2008) found
that after observing the oval entity turn toward one of two targets, 14- to 15-month-olds turned
in the same direction if the entity first conversed with an experimenter (agent condition) but not
if it beeped and the experimenter remained silent (nonagent condition).
The preceding results have been replicated and extended in other laboratories (e.g., Beier
& Carey 2014, Deligianni et al. 2011). In one attention-following task, for example, 12- to 13-
month-olds perceived a rounded brown entity as agentive if it responded with beeps when the
experimenter clapped his hands playfully toward it, but not if it first responded with beeps when
the experimenter clapped two sticks toward it with a neutral expression (Beier & Carey 2014). This
negative result suggests that mere turn-taking does not provide sufficient evidence for agency: The
entity must demonstrate that it can not only detect events in its environment, but also respond to
them in a goal-directed manner, as when participating in a conversation or a playful interaction.
When the experimenter clapped sticks and the entity beeped in response, infants were unable to
interpret its actions as goal directed, and they therefore did not identify it as an agent.
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In the preceding experiments, the novel entity interacted with a human experimenter; in other
experiments, no experimenter was involved, and infants viewed the entity as agentive if it gave
evidence that it detected and responded purposely to changes in the scene (e.g., the introduction
of objects, a change to the size of an obstacle, or the approach of another entity; B´
ır ´
o et al. 2007,
Hernik & Southgate 2012, Luo & Baillargeon 2005a, Schlottmann et al. 2012). In one preference
task, for example, 5-month-olds first saw a box move back and forth at the center of an apparatus
(Luo & Baillargeon 2005a). Next, object A and object B were added, and the box approached and
rested against object A. Infants interpreted the change in the box’s behavior as evidence that it was
agentive; as a result, they attributed to the box a preference for object A, and they looked longer
when it approached object B in the test trials. Interestingly, this effect was eliminated if a long
handle was attached to the box, with the end of the handle protruding through the sidewall of
the apparatus; it was then unclear whether the box had autonomous control over its actions, and
infants no longer viewed it as an agent.
Choosing goals or means. When no change occurs in a scene, infants may still perceive a novel
entity as agentive if it gives evidence that it is choosing either which target to approach or which
(efficient) path to follow to a target. In preference tasks, 6- and 12-month-olds viewed a novel
entity as agentive (as evidenced by their looking longer at the new-object event in the test trials) if
it “turned” toward object A before approaching it in the familiarization trials, as though choosing
it as its goal object ( Johnson et al. 2007b, Schlottmann & Ray 2010). In a detour task, Csibra
(2008) familiarized 6-month-olds with an event in which a box had to move around an obstacle
to reach a target. Infants viewed the box as agentive (as evidenced by their looking longer at the
old-path event in the test trials) if it detoured randomly around the left or the right side of the
obstacle across the familiarization trials, as though choosing its path in each trial. In contrast,
infants did not identify the box as an agent if it approached the target using the same fixed path
around the obstacle in every familiarization trial. This negative result provides further evidence
that for infants, self-propulsion and the repeated production of a single, fixed action that could be
described as a goal-directed action do not provide sufficient evidence for agency (from an adult
perspective, a mechanical device such as a ceiling fan would show these same abilities).
Self-Propelled Objects, Agents, and Animals
Although self-propulsion is not sufficient for infants to identify a novel entity as an agent, it could
still be necessary for them to do so. Are infants able to view inert objects as agents, as adults are (e.g.,
the Magic Mirror in the Snow White fairy tale)? This question has received little experimental
attention to date, but preliminary evidence suggests that infants identify an inert object as an
agent if it demonstrates autonomous control over its communications (e.g., if it beeps when object
A, but not object B, is revealed; Baillargeon et al. 2009). This initial evidence, paired with the
results reviewed in the preceding section and additional findings on infants’ expectations about
self-propelled objects and animals (e.g., Baillargeon et al. 2009, Leslie 1994, Luo et al. 2009,
Newman et al. 2008, Setoh et al. 2013), suggests three conclusions. First, self-propulsion and
agency are distinct concepts for infants: An object may be self-propelled without being agentive,
and it may be agentive without being self-propelled. A self-propelled object has an internal source
of physical energy that allows it to exert or resist physical forces; an agentive object has mental
states that give it control over its actions. Second, objects that are both self-propelled and agentive
are categorized as animals and endowed with additional, biological properties such as innards.
In a series of experiments, 8-month-olds detected a violation when a novel entity that was both
self-propelled and agentive was revealed to be hollow, but they detected no such violation when
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the entity was only self-propelled, only agentive, or neither self-propelled nor agentive (Setoh
et al. 2013). Third, these various results suggest that at least three core causal-reasoning systems
(and their associated concepts) operate seamlessly to guide infants’ responses to novel entities:
the physical-reasoning system (energy), the psychological-reasoning system (mental states), and
the biological-reasoning system (innards). As Keil (1995) emphasized, these early abstract causal
understandings are very shallow and divorced of all mechanistic detail; nevertheless, they play a
critical role in orienting infants to construe entities and their causal powers effectively.
Predictive Cues
We have seen that infants identify a novel entity as an agent if it gives evidence of internal control
over its actions. This identification process may be relatively slow, however, so it makes sense that
infants would also use their discrimination and categorization abilities to learn which perceptual
cues predict agency.
Because most of the agentive entities infants encounter in daily life are humans and nonhuman
animals (henceforth animals), predictive cues for agency will include motion cues (e.g., biological
motion), morphological cues (e.g., having a face, a humanoid form, or a four-legged form), and
surface-texture cues (e.g., having fur). Not surprisingly, given their intense interest in humans
and animals (e.g., LoBue et al. 2013), infants rapidly begin to learn these cues and to use them
in identifying novel agents (e.g., Arterberry & Bornstein 2002, Johnson et al. 2001, Kamewari
et al. 2005, Setoh et al. 2013, Tr¨
auble & Pauen 2011, Yoon & Johnson 2009). In a detour task,
for example, 6.5-month-olds identified a humanoid robot as an agent even though it followed the
same fixed path around the obstacle in each familiarization trial (Kamewari et al. 2005). Similarly,
in attention-following tasks, 12-month-olds turned in the same direction as a point-light human
in an upright position (Yoon & Johnson 2009) or as a novel rounded entity with a face and fur
( Johnson et al. 2001).
ATTRIBUTING MOTIVATIONAL STATES
The initial findings of Gergely, Csibra, and Woodward (reviewed previously) indicated that infants
can attribute to agents motivational states such as goals and dispositions. Subsequent research has
extended these findings in several directions, as summarized below.
Goals
By their first birthday, infants can infer a variety of goals, including inspecting, reaching, obtaining,
or displacing an object; comforting, helping, hindering, chasing, or hitting an agent; and giving
a toy to an agent or stealing a toy from an agent (Csibra et al. 2003; Hamlin & Wynn 2011;
Johnson et al. 2007a, 2010; Kir´
aly et al. 2003; Kuhlmeier et al. 2003; Luo & Baillargeon 2005a;
Premack & Premack 1997; Woodward 1998). Moreover, infants understand not only single goal-
directed actions, but also more complex means-end action sequences. In a preference task with
12-month-olds, for example, object A and object B rested inside separate containers, and in each
familiarization trial the agent opened object A’s container in order to retrieve it (Woodward &
Sommerville 2000). In the test trials, the objects switched containers, and the agent grasped either
the old (old-container event) or the new (new-container event) container and paused. Infants
looked longer at the old- than at the new-container event, suggesting that they attributed to the
agent a preference for object A and understood that her intermediate actions on its container
merely served her overarching goal of obtaining object A. As was found in detour tasks, infants
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demonstrated sensitivity to the efficiency principle in their interpretations of the agent’s means-
end actions: If object A stood next to (as opposed to inside) its container in the familiarization
trials, infants could no longer make sense of the agent’s inefficient actions (i.e., why did she first
open the container next to object A?), and they held no expectation about her actions in the test
trials (see also B´
ır ´
o et al. 2011).
Infants also demonstrate their ability to identify goals in imitation tasks. For example, infants
are more likely to imitate actions that are marked as intentional (“There!”) than actions that are
marked as accidental (“Woops”) (e.g., Carpenter et al. 1998, Olineck & Poulin-Dubois 2005);
they are equally likely to reproduce intended outcomes after watching successful or incomplete
demonstrations (e.g., Meltzoff 1995, Olineck & Poulin-Dubois 2009); and they are more likely
to reproduce goal-relevant than goal-irrelevant action components (e.g., Brugger et al. 2007,
Carpenter et al. 2005).
Although infants can understand a variety of goals, there are of course situations where they
will fail to identify an agent’s particular goal, for a variety of reasons. In some cases, infants may
simply lack the relevant knowledge to infer the goal of a novel action. We can easily imagine that
infants may be nonplussed when they first observe a parent listen to a cell phone, point a remote
key at a car, or lick a fingertip before turning a page; infants may appreciate that the parent is
acting purposely but be uncertain about what outcomes these actions are meant to achieve. In line
with this analysis, 9-month-olds failed at a preference task in which an agent placed the back of her
hand against object A in the familiarization trials instead of grasping it; because infants could not
infer the goal of this baffling back-of-hand action, they looked equally at the new- and old-object
events (Woodward 1999). Several investigations have taken advantage of this negative result to
examine what experiences might lead infants to view the back-of-hand action as a goal-directed
action (e.g., B´
ır ´
o et al. 2014, Kir´
aly et al. 2003; for similar investigations with other novel actions,
see, e.g., Gerson & Woodward 2012, 2013). In one experiment, for example, an experimenter and
12-month-olds first took turns lifting Velcro-covered blocks using a Velcro band worn on the back
of their hands (B´
ır ´
o et al. 2014). After this training session, infants received a preference task in
which an agent wearing a similar Velcro band produced back-of-hand actions, without lifting the
objects. Results were positive, suggesting that the training session helped infants view the agent’s
back-of-hand actions as goal directed; as a result, infants attributed to the agent a preference for
the object she repeatedly chose, and they expected her to maintain this preference in the test trials,
in accordance with the consistency principle.
In other cases, infants may possess the relevant knowledge to identify an agent’s goal but have
difficulty doing so because the scene does not provide sufficient information to guide or support
their reasoning. In one imitation task, for example, 16-month-olds first watched an experimenter
demonstrate the use of a novel T-shaped rake to retrieve a toy out of reach (Esseily et al. 2013).
When encouraged to do the same, infants showed some success only if the experimenter had first
made clear the goal of her actions by stretching her arm and hand toward the out-of-reach toy,
as though vainly trying to grasp it. In other investigations, 3-month-olds succeeded at detour
and preference tasks only if they were first primed to focus on the goal of the agent’s actions
(e.g., Skerry et al. 2013, Sommerville et al. 2005). In one investigation, for example, infants in
the experimental condition first received a brief play session in which they wore Velcro mittens
(adapted from Needham et al. 2002) that allowed them to pick up Velcro-covered toys by swiping
at them (Skerry et al. 2013). Next, infants received a detour task involving videotaped events: In
the familiarization trials, an agent wearing a similar Velcro mitten reached over a barrier to get
a toy and then paused; in the test trials, the barrier was removed and the agent reached for the
toy either in a straight line (new-path event) or using the same arching action as before (old-path
event). Infants looked longer at the old- than at the new-path event; in contrast, infants who wore
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mittens without Velcro during the play session, or who did not receive a play session, looked about
equally at the two events. Together, these results suggest that the experimental play session, where
swipes brought about observable outcomes, helped infants focus on and extract the goal of the
agent’s actions in the detour task. Once infants had identified this goal, they expected the agent to
pursue it efficiently, in accordance with the efficiency principle. Although the young infants in this
experiment were unable to focus on the agent’s goal without an appropriate priming experience
(see also Gerson & Woodward 2014, Sommerville et al. 2005), it is unlikely that such an experience
is always necessary, as positive results have been obtained with 3-month-olds in tasks involving
richer or less minimal actions (e.g., Hamlin et al. 2010, Luo 2011b).
Finally, in situations where infants succeed in identifying an agent’s goal, they expect the agent’s
subsequent actions to abide not only by the efficiency principle, as we have seen, but also by the
consistency principle. First, infants detect a violation if an agent changes goal for no apparent
reason. Thus, after watching familiarization trials in which a large circle chased a small circle in
a scene, 12-month-olds detected a consistency violation in the test trials if the large circle caught
up with the small circle and continued moving past it, as though ignoring it, instead of stopping
against it (Csibra et al. 2003). Second, infants detect a violation if an agent shows an inappropriate
emotional reaction following the attainment of a goal (Skerry & Spelke 2014). After watching
a circle successfully jump over an obstacle to reach a target, 8- and 10-month-olds detected a
consistency violation if the circle displayed a negative emotional reaction (frowning, crying, and
rocking) as opposed to a positive emotional reaction (smiling, giggling, and bouncing).
Preferences
Modifications of the preference task have yielded many additional insights into infants’ ability to
attribute preferences. First, when watching an agent repeatedly choose object A over object B in
the familiarization trials, infants attribute to the agent not simply a preference for that object in
particular, but rather a preference for that object category in general (Spaepen & Spelke 2007).
Thus, after seeing an agent repeatedly choose a black female doll over an orange dump truck (or
the reverse), 12-month-olds attributed to the agent a preference for dolls (or trucks), and they
expected the agent to reach for the toy from the preferred category even when new toys (a white
male doll and a red tow truck) were used in the test trials.
Second, infants can use not only unvarying-choice information (i.e., the agent always chooses
object A over object B), but also other types of information to attribute a preference to an agent.
One type is emotional information: If an agent emotes positively toward one toy but negatively
toward another toy, infants attribute to the agent a preference for the first toy (e.g., Barna &
Legerstee 2005, Egyed et al. 2013). Another type is statistical information: If an agent chooses
only toy ducks from a box that contains mostly toy frogs, infants infer that the agent prefers the
ducks (e.g., Gweon et al. 2010, Kushnir et al. 2010). Yet another type is effort information: If
an agent faces a single toy but has to go to some effort to obtain it in each familiarization trial
(e.g., has to open a container or detour around an obstacle to retrieve it), infants conclude that
the agent must have a positive disposition toward the toy. As might be expected, only rational
effort matters: Infants do not attribute a positive disposition if the agent’s effortful actions are
inefficient because the toy stands next to the container or the detour is wider than necessary (e.g.,
B´
ır ´
o et al. 2011, Hernik & Southgate 2012). A final type of information, equifinality information,
may constitute a special case of effort information: If an agent faces a single toy and approaches
it in every familiarization trial even though the toy’s position keeps changing (suggesting that the
agent is willing to adjust its actions as needed to contact the toy), infants again conclude that the
agent has a liking for the toy (Luo 2011b).
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Third, infants recognize that preferences are attributes of individual agents: Mommy prefers
white wine, but daddy prefers beer; big sister Jane is fond of sports, but big brother Karl likes video
games. Thus, after watching familiarization trials in which agent A demonstrates a preference for
object A over object B, infants age 9 months and older hold no expectation about which of the
two objects a new agent, agent B, will prefer (e.g., Buresh & Woodward 2007, Henderson &
Woodward 2012). An important exception is that infants do generalize preferences demonstrated
in “pedagogical” contexts to other agents (Csibra & Gergely 2009). In an experiment with 18-
month-olds (Egyed et al. 2013), agent A emoted positively toward object A and negatively toward
object B, and then she left the room. Next, agent B arrived and asked the infants to give her
one of the objects. If agent A used ostensive-communicative signals (e.g., looked at, smiled at, and
greeted the infants) before and during her emotional displays, infants (a) interpreted these displays
as pedagogical encounters aimed at teaching them the properties of the objects, (b) inferred that
object A was pleasing but object B was not, and (c) expected agent B to share the same knowledge
and preference and so gave her object A.
Fourth, in addition to preferences for objects (e.g., dolls), infants can attribute other types
of preferences to agents. One type involves preferences for particular activities. After seeing an
agent slide different objects, one at a time, forward and backward on an apparatus floor, 9- and
13-month-olds attributed to the agent a predilection for sliding objects, and they expected the
agent to select a slidable over an unslidable object in the test trials (Song & Baillargeon 2007,
Song et al. 2005). Another type of preference is for particular colors. After seeing that an agent
preferred a red toy pepper over a black cup, and a red toy pyramid over a yellow toy house, 16-
month-olds attributed to the agent a preference for red objects, and they expected the agent to
select a new red object over a new green object in the test trials (Luo & Beck 2010). In recent
experiments, 16-month-olds failed to attribute a color preference to an agent who consistently
reached for a red football over a yellow football, no doubt because both toys belonged to the same
object category (Mou et al. 2014). However, if infants saw the agent choose the red football over
the yellow football in three familiarization trials, and then they saw the agent choose the yellow
football over a green football in the next three familiarization trials, they concluded that the agent
had an ordered set of preferences, and they expected the agent to prefer the red football over the
green football when presented with both in the test trials.
Emotional States
To date, there has been little attention to the question of whether infants understand that emotions
and moods, like goals and dispositions, can motivate agents’ actions in a scene. As adults, we readily
understand that an angry boy may kick rocks in his path or that a teenager looking forward to a
date may sing happily in the shower. At what age do infants begin to understand that emotions may
motivate (as opposed to simply accompany) actions? Such understanding appears to be present at
least by the second year of life (Hepach & Westermann 2013). In one experiment, 14-month-olds
saw two agents who were at times angry or happy perform actions that were either congruent or
incongruent with their current moods. Infants showed greater sympathetic activity (as measured
by pupil dilation) when an agent in an angry mood gently patted a toy or when an agent in a happy
mood hit the toy.
Predicting Others’ Actions
As evidence steadily accumulated that infants could infer agents’ motivational states, researchers
began to ask whether infants could use these states not only to interpret but also to predict
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agents’ actions (e.g., Henrichs et al. 2014, Hunnius & Bekkering 2010, Kanakogi & Itakura 2011).
As Brandone et al. (2014) stated, “a prospective intentional stance is fundamental to interpreting
actions in real-time social situations and thus to interacting seamlessly with others” (p. 23).
The use of eye-tracking methodology has made it possible to examine in great detail under what
conditions infants produce predictive looks that reflect their understanding of agents’ motivational
states. With this methodology, infants have been found to correctly anticipate agents’ actions in
detour tasks (e.g., B´
ır ´
o 2013) and in preference tasks (e.g., Cannon & Woodward 2012, Kim
& Song 2015). In one preference task, for example, 11-month-olds received four trials, each
of which had three phases involving different movie clips (Cannon & Woodward 2012). In the
familiarization phase, object A and object B rested in the top and bottom right corners of the
monitor; a hand entered from the left, moved straight across the scene, and deflected just past
midline to grasp object A. This event was repeated three times. In the next phase, the object’s
positions were switched. In the test phase, the hand moved as before but paused just past midline.
Infants were more likely to make their first look from the hand to object A, suggesting that they
attributed to the agent a preference for this object and anticipated that the agent would reach for
it again.
Analyses of infants’ brain activity during preference tasks also provide evidence of predictive
psychological reasoning (Southgate & Begus 2013). In one experiment, 9-month-olds watched
videotaped events while their sensorimotor-cortex activation was measured using electroen-
cephalography (EEG). Infants first received familiarization trials in which an agent’s hand
consistently reached for and grasped object A as opposed to object B. Next, infants received
several test trials; each included a baseline period (a moving screensaver) and a static anticipatory
period in which either object A or object B was present and the hand rested in front of it.
Comparison of the baseline and static periods showed greater motor activation during the test
trials involving object A. Thus, infants anticipated that the agent would reach when preferred
object A was present, but they showed no such anticipation when object B was present.
Making Sense of Irrational Actions
We have seen that when an agent produces irrational actions (e.g., makes an unnecessary detour
while approaching a target or opens a container before grasping a toy next to it), infants hold no
expectation about the agent’s subsequent actions. But are there situations where infants succeed in
generating explanations for apparently irrational actions? Research on this question has focused
on pedagogical cues and situational constraints.
Pedagogical cues. Infants interpret inefficient actions differently when the actions are accom-
panied by pedagogical signals. Kir´
aly et al. (2013) built on a puzzling finding from an imitation
task by Meltzoff (1988): After watching a model activate a light-box by touching it with his
forehead, 14-month-olds were more likely to reproduce this action one week later than were
control infants. Why did the infants imitate this inefficient head action instead of using the more
efficient approach of touching the light-box with their hands? Kir´
aly et al. (2013) speculated
that the ostensive-communicative cues that accompanied the model’s demonstrations signaled
to the infants that he was attempting to teach them the conventional use of this novel object.
To examine this speculation, Kir´
aly and colleagues tested 14-month-olds in two conditions.
In the communicative condition, a model provided ostensive-communicative signals (e.g., she
looked at and spoke to the infants) before and between her head actions on the light-box. In the
noncommunicative condition, the model performed the same demonstrations without interacting
with the infants. After a 10-minute delay, infants in both conditions were presented with the
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light-box for 20 seconds. Although all infants first used their hands to activate the light-box, 65%
of the infants in the communicative condition also attempted at least once to perform the head
action (this effect was replicated in another experiment with a one-week delay); in contrast, only
29% of the infants in the noncommunicative condition did so. The authors concluded that the
head action, when accompanied by pedagogical cues, was “learned as a culturally relevant novel
instrumental means that ought to be used to operate the novel artifact” (Kir´
aly et al. 2013, p. 482).
Situational constraints. Infants make use of situational constraints to generate explanations for
actions that would otherwise violate the efficiency principle. In another imitation task with a light-
box, Gergely et al. (2002) found that 14-month-olds were less likely to reproduce a model’s head
action one week later if her hands were occupied during the demonstration (the model wrapped
herself in a blanket that she held with both hands) than if her hands were free (the model wore
the blanket loosely and laid her hands on either side of the light-box). Infants thus attended to
the constraints affecting the model’s actions: When her hands were occupied, they interpreted
her inefficient head action simply as an expedient, alternative means of activating the light-box.
Similar results have been obtained in other laboratories (e.g., Paulus et al. 2011, Pinkham & Jaswal
2011, Schwier et al. 2006).
Infants also attend to situational constraints to make sense of actions that appear to violate the
consistency principle. Luo (2010) built on a puzzling finding from a preference task by Woodward
(2003): When an agent simply looked intently at object A (as opposed to object B) in the famil-
iarization trials, without grasping it, 12-month-olds still succeeded in attributing to the agent a
preference for object A, but 7- and 9-month-olds did not (i.e., they looked equally at the new- and
old-object test events). One possible interpretation of this negative result was that the younger
infants detected a consistency violation: If the agent wanted object A, as her attentional behavior
suggested, why did she not take it, since it was within her reach and there was no obstacle in her
way? In line with this interpretation, Luo (2010) found that 8-month-olds succeeded in attributing
a preference for object A to the agent if the scene was modified to provide an explanation for her
failure to reach: Either her hands were occupied holding the two handles of a sippy cup or she
sat behind a small window that only allowed her to look at the objects. These results suggest that
whereas 8-month-olds are in the habit of reaching for interesting objects within easy reach and
interpret others’ actions accordingly, 12-month-olds have learned (perhaps via parental admoni-
tions during their expanding locomotor forays) that one may sometimes look at, but not touch,
interesting objects.
ATTRIBUTING EPISTEMIC STATES
When interpreting an agent’s actions in a scene, do infants consider not only the agent’s
motivation, but also the knowledge the agent possesses or lacks about the scene? To address
this question, researchers have explored infants’ ability to reason about epistemic states such
as knowledge and ignorance. A critical issue has been whether infants (a) are fundamentally
egocentric and as such incapable of attributing to an agent a representation of a scene that differs
from their own or (b) are nonegocentric and able to recognize, at least in some situations, that an
agent’s knowledge about a scene may be less complete than their own.
Keeping Track of What Objects Agents Can See or Have Seen
Do infants attend to what objects an agent can or cannot see, and has or has not seen, and expect
the agent to know about the seen objects but to be ignorant about the unseen objects? To shed
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light on these questions, several experiments have used preference tasks in which object B is
hidden from the agent—but not the infants—during the familiarization trials; the rationale is that
if infants realize that the agent can see object A but not object B, they should perform as infants
typically do when only object A is present in the familiarization trials (Kim & Song 2015, Luo &
Baillargeon 2007, Luo & Johnson 2009). In one experiment, 12-month-olds were assigned to an
ignorance or a knowledge condition (Luo & Baillargeon 2007). In the familiarization trials of the
ignorance condition, the agent sat centered behind a transparent screen and an opaque screen;
object A stood in front of the transparent screen, and object B stood in front of the opaque
screen (object B was thus visible to the infants but not the agent). In each familiarization trial, the
agent reached around the transparent barrier and grasped object A. In the test trial, the screens
were removed, the objects’ positions were switched, and the agent reached for either object A
(old-object event) or object B (new-object event). The knowledge condition was identical except
that before the familiarization trials the agent placed object B in front of the opaque screen herself
and thus knew of its presence there. Infants in the knowledge condition looked longer if shown
the new-object as opposed to the old-object event, whereas infants in the ignorance condition
looked equally at the two events. Thus, infants took into account the agent’s knowledge when
interpreting her actions during the familiarization trials. When the agent knew both objects were
present, infants interpreted her repeated actions on object A as demonstrating a preference for
that object. In contrast, when the agent was ignorant about object B’s presence in the scene,
infants realized that her actions on object A could not be interpreted as signaling a preference (i.e.,
she might be reaching for object A simply because she thought it was the only object present).
These findings were subsequently extended to 6-month-olds (Kim & Song 2015, Luo &
Johnson 2009). For example, in an anticipatory-looking task modeled after that of Luo &
Baillargeon (2007), Kim & Song (2015) found that infants in the knowledge condition anticipated
that the agent would reach for object A in the test trial, whereas infants in the ignorance condition
showed no such anticipation. These results indicate that at least by 6 months of age, infants are
nonegocentric: If an agent’s representation of a scene is incomplete relative to their own, they
use the agent’s representation to predict and interpret the agent’s actions.
By the second year of life, infants also use the agent’s representation to guide their own actions
in the scene. For example, Tomasello & Haberl (2003) found that when an agent requested one of
three objects excitedly, 12- and 18-month-olds gave her the one she had not seen previously, sug-
gesting that they kept track of which objects the agent had experienced during the testing session.
Repacholi et al. (2008) also reported that after watching an agent angrily scold an experimenter
for playing with an “irritating” toy, 18-month-olds were more likely to play with the toy if the
agent did not look at them (e.g., if she read a magazine) than if she looked at them directly.
Finally, infants in the second year of life realize that just as they may see an object that an
agent cannot see, an agent may see an object that they themselves cannot see (e.g., Chow et al.
2008, Moll & Tomasello 2004). For example, Moll & Tomasello (2004) found that when an agent
looked behind an opaque barrier with expressions of excitement, 12- and 18-month-olds crawled
or walked forward to peek around the barrier and see what the agent could see.
Keeping Track of What Events Agents Have Seen
Infants keep track of what events an agent has or has not witnessed in a scene, and they attribute
appropriate epistemic states to the agent: They expect an agent who has witnessed an event to
know about it, and they expect an agent who has not witnessed an event to be ignorant about
it. For example, if an agent is present while an experimenter hides a preferred toy in one of two
boxes, infants ages 6 to 18 months expect the agent to know the toy’s location and to search
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the correct box, and they detect a violation if the agent searches the incorrect box instead (e.g.,
Z. He and R. Baillargeon, manuscript in preparation; Scott & Baillargeon 2009; Song & Bail-
largeon 2008; Surian et al. 2007). Conversely, if the agent is absent while the toy is hidden, infants
expect the agent to be ignorant about the toy’s location and to search either box at random (Z. He
and R. Baillargeon, manuscript in preparation; Scott & Baillargeon 2009). These results provide
additional evidence that infants are nonegocentric and realize that an agent may know less about a
scene than they do. In addition, these results make clear that infants expect agents to act in a manner
consistent with both their motivational and epistemic states: An agent who wants her preferred toy
and knows its location should search that location, in accordance with the consistency principle.
By the second year of life, infants use the knowledge available to an agent not only to interpret
but also to predict the agent’s actions (e.g., Meristo et al. 2012, Surian & Geraci 2012). In one
anticipatory-looking task, for example, 17-month-olds watched events in which a triangle chased a
circle, which finally hid in one of two boxes (Surian & Geraci 2012). When the triangle witnessed
this hiding event, infants anticipated that it would approach the correct box to find the circle.
Finally, infants’ understanding of an agent’s epistemic states also guides their own actions toward
the agent. Thus, infants age 12 months and older spontaneously pointed to inform an agent about
the current location of an object if she was absent when it was moved to a new location (Liszkowski
et al. 2006) or if she was looking away when it fell to the floor (Liszkowski et al. 2008).
Evaluating Irrational Agents: The Case of Epistemic Unreliability
We saw previously that when an agent acts irrationally (e.g., performs an unnecessary detour en
route to a target), infants typically hold no expectation about the agent’s subsequent actions. In
some cases, infants may simply conclude that they lack sufficient information to understand the
agent’s actions. In other cases, however, infants may evaluate the agent as irrational and withhold
future expectations, both in the original context in which the irrational action occurred as well as
in new contexts; for infants as for adults, it is difficult to predict the actions of irrational agents
or to trust new information they impart. Evidence for this second possibility comes from tasks on
epistemic unreliability, which contrast reliable agents who act in accordance with their epistemic
states and unreliable agents who do not.
In a series of unreliable-looker tasks, Poulin-Dubois and her colleagues tested whether 14- to
16-month-olds who saw an agent act in a manner inconsistent with her epistemic states in a first
context would then hold no expectation about her behavior in a second context. In the first context,
the agent expressed excitement (“Wow!”) when looking inside a bucket that either contained a toy
(reliable-looker condition) or was empty (unreliable-looker condition). The second context was
adapted from prior tasks and varied across experiments, but in each case infants held expectations
for the actions of the reliable but not the unreliable looker. Thus, infants were more likely to peek
around a barrier after watching the reliable looker express excitement as she looked behind the
barrier (Chow et al. 2008); they were more likely to detect a violation if the reliable looker failed
to use her knowledge of an object’s location when searching for it (Poulin-Dubois & Chow 2009);
and they were more likely to activate a light-box with their foreheads after watching the reliable
looker perform this novel inefficient action (Poulin-Dubois et al. 2011).
In an unreliable-user task, Zmyj et al. (2010) first showed 14-month-olds events in which an
agent used everyday objects in either the typical manner (reliable-user condition; e.g., putting sun-
glasses on his nose and using a toothbrush to brush his teeth) or an atypical manner (unreliable-user
condition; e.g., putting sunglasses on his foot and using a toothbrush to brush his hand). Next, the
agent activated a light-box with his forehead, and infants in the reliable-user condition were more
likely to imitate this novel inefficient action than were infants in the unreliable-user condition.
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Finally, unreliable-labeler tasks take advantage of the fact that infants in the second year of
life already know labels for many familiar objects (e.g., Begus & Southgate 2012, Brooker &
Poulin-Dubois 2013, Koenig & Woodward 2010, Krogh-Jespersen & Echols 2012). In one task,
for example, 18-month-olds first watched an agent label familiar objects either correctly (reliable-
labeler condition) or incorrectly (unreliable-labeler condition). Infants were more likely to learn a
novel label and to imitate a novel inefficient action taught by the reliable labeler as opposed to the
unreliable labeler (Brooker & Poulin-Dubois 2013). Similarly, 16-month-olds were more likely
to point to novel objects—as though requesting information about these objects (Kov´
acs et al.
2014b)—if faced with a reliable as opposed to an unreliable labeler (Begus & Southgate 2012).
The preceding results suggest two broad conclusions. First, infants evaluate an agent who acts in
a manner inconsistent with her epistemic states as irrational: They are less likely to seek information
from her, to learn novel words and actions from her, or to detect a violation when she acts
irrationally in a new context. This evaluation appears to be psychological rather than sociomoral
in nature: 18-month-olds were equally likely to help a reliable or an unreliable labeler by bringing
closer an object out of reach (Brooker & Poulin-Dubois 2013). Second, the preceding results extend
our understanding of the consistency principle. Until now, our discussion of consistency violations
has focused on situations where an agent with a demonstrated goal or preference suddenly deviated
from it, for no apparent reason. What the research on epistemic unreliability makes clear is that in
assessing consistency, infants bring to bear what they have learned from their social environments
about how agents typically react to situations, use or label objects, and so on. Thus, an agent who
emotes positively over an empty bucket, puts sunglasses on her foot, or labels a ball as a shoe
is an agent who violates the consistency principle, given shared societal norms and conventions
(for an interesting exception showing infants’ sensitivity to humor cues, see Hoicka & Wang
2011).
ATTRIBUTING COUNTERFACTUAL STATES
The evidence reviewed in the preceding section indicates that beginning in the first year of life,
infants recognize that agents may at times be ignorant about some aspect of a scene. But what
happens when agents are not merely ignorant but hold false beliefs about a scene? Are infants able
to reason about counterfactual states such as false beliefs?
For many years, it was widely assumed that the ability to attribute false beliefs did not emerge
until about 4 years of age (e.g., Gopnik & Astington 1988, Wellman et al. 2001, Wimmer &
Perner 1983). The evidence for this conclusion came primarily from elicited-prediction tasks
in which children were asked to predict the behavior of an agent who held a false belief about
a scene. In a classic task (Baron-Cohen et al. 1985), children listened to a story enacted with
props: Sally hid a marble in a basket and then left; in her absence, Anne moved the marble to a
nearby box; Sally then returned, and children were asked where she would look for her marble.
Most 4-year-olds answered correctly and pointed to the basket (where Sally falsely believed the
marble was); in contrast, most 3-year-olds pointed to the box (where the marble actually was),
suggesting that they did not yet understand that Sally would hold a false belief about the marble’s
location.
Over the past decade, the conclusion that false-belief understanding does not emerge until the
preschool years has been called into question by steadily accumulating evidence that children in
the third, second, and even first year of life demonstrate such understanding when tested with
other types of false-belief tasks (e.g., Baillargeon et al. 2010, 2015). Positive results have now been
obtained with infants in spontaneous-response and elicited-intervention tasks. In both types of
tasks, infants watch a scene in which an agent comes to hold a false belief. In spontaneous-response
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tasks, infants are asked no test question; instead, their spontaneous responses to the unfolding scene
are measured. In elicited-intervention tasks, infants are asked a test question that prompts them
to perform some action for the mistaken agent.
Spontaneous-Response False-Belief Tasks
The first spontaneous-response task with infants used the violation-of-expectation method and
examined whether 15-month-olds would expect an agent to act in accordance with her false belief
about a toy’s location (Onishi & Baillargeon 2005). Infants first received familiarization trials in
which an agent hid a toy in a green as opposed to a yellow box. Next, infants received one of four
different belief-induction trials that resulted in the agent believing, truly or falsely, that the toy was
in the green or the yellow box: In the knowledge-green condition, the agent watched as the yellow
box moved a short distance and then returned to its original position; in the false-belief-green
condition, the agent was absent when the toy moved from the green box into the yellow box; in
the knowledge-yellow condition, the agent saw the toy move into the yellow box; and finally, in
the false-belief-yellow condition, the agent watched as the toy moved into the yellow box, but
was absent when it returned to the green box. In the test trial, the agent reached into either the
green or the yellow box and then paused. In each condition, infants expected the agent to act on
the information available to her, whether it was true or false; thus, infants in the knowledge-green
and false-belief-green conditions expected the agent to reach into the green box, whereas infants
in the knowledge-yellow and false-belief-yellow conditions expected her to reach into the yellow
box. In each case, infants detected a consistency violation when the agent searched the other
box.
The results of Onishi & Baillargeon (2005) have been confirmed and extended in many other
spontaneous-response tasks. First, infants’ reasoning about false beliefs about location (like their
reasoning about other mental states) is highly context sensitive. For example, infants expect an
agent not to hold a false belief about an object’s location (a) if she wears a see-through as opposed
to an opaque blindfold while the object is moved (Senju et al. 2011), (b) if she can see part of
the object in its new location when she returns (Surian et al. 2007), (c) if she is given relevant
information (e.g., “The ball is in the cup!”), as opposed to irrelevant information (e.g., “I like the
cup!”), about the object’s new location (Song et al. 2008), and (d) if the object rolls down a beam
to its new location because the agent tipped the beam with her hand while looking away (Tr¨
auble
et al. 2010).
Second, infants understand not only false beliefs about the location of an object, but also false
beliefs about the presence, properties, and identity of an object (e.g., Scott & Baillargeon 2009,
Scott et al. 2010, Song & Baillargeon 2008, Southgate & Vernetti 2014). In a task on identity
(Scott & Baillargeon 2009), for example, 18-month-olds first received familiarization trials in
which an agent faced a one-piece penguin that did not come apart and a disassembled two-piece
penguin. In each trial, the agent hid a small key in the bottom piece of the two-piece penguin and
then assembled it; once assembled, the two-piece penguin was identical to the one-piece penguin.
In the test trials, while the agent was absent, an experimenter assembled the two-piece penguin,
placed it under a transparent cover, and then placed the one-piece penguin under an opaque cover.
The agent then returned with her key and reached for either the transparent or the opaque cover
and then paused. Infants expected the agent to reach for the opaque cover and looked longer
when she reached for the transparent cover instead (this looking pattern reversed if the agent
witnessed the experimenter’s actions). These results indicated that infants expected the agent
(a) to mistake the penguin visible under the transparent cover for the one-piece penguin (because
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the two-piece penguin had always been disassembled at the start of the familiarization trials)
and hence (b) to falsely conclude that the disassembled two-piece penguin was hidden under the
opaque cover (because both penguins were always present in the familiarization trials). Infants
thus attributed to the agent not just one but two interlocking false beliefs.
Third, infants take into account an agent’s false belief(s) not only to interpret the agent’s actions
(e.g., to understand why the agent approaches the wrong location to find a desired object), but also
to predict the agent’s actions and to guide their own actions toward the agent. In anticipatory-
looking tasks, 17- to 25-month-olds spontaneously anticipated that an agent who believed an
object was in location A (when it was in fact in location B or had been removed from the scene)
would search location A for the object (e.g., Meristo et al. 2012, Senju et al. 2011, Southgate
et al. 2007, Surian & Geraci 2012). In anticipatory-pointing tasks, 18-month-olds spontaneously
pointed to inform a mistaken agent that an object had been moved to a new location (Knudsen &
Liszkowski 2012a) or that an aversive object had been placed at the location she falsely believed
held her desired object (Knudsen & Liszkowski 2012b).
Fourth, the evidence that infants represent others’ false beliefs now extends to the first year
of life (e.g., Kov´
acs et al. 2010, Luo 2011a, Southgate & Vernetti 2014). In a looking-time task,
for example, 7-month-olds first received familiarization trials in which a Smurf agent placed a
self-propelled ball in front of an occluder; the ball then moved behind the occluder, which was
lowered to reveal the ball. In the test trials, infants saw a knowledge and a false-belief event. In
the knowledge event, the agent again introduced the ball and watched as it first moved behind
the occluder and then exited the scene; finally, the occluder was lowered to reveal no ball. The
false-belief event was identical except that the agent left after the ball moved behind the occluder
and returned only after the ball had exited the scene. Infants looked longer at the false-belief than
at the knowledge event, and this effect was eliminated if the occluder was not lowered at the end
of the events. These and other results indicated that when watching the false-belief event, infants
expected the agent (a) to falsely believe the ball was still present behind the occluder and hence
(b) to be surprised by the ball’s disappearance and perhaps also to generate an explanation for it (as
do 6-month-olds when a self-propelled object slips out of view to a new location; Luo et al. 2009).
Evidence that young infants can not only interpret but also predict the actions of mistaken agents
comes from an EEG experiment that measured 6-month-olds’ sensorimotor cortex activation as
they watched false-belief events (Southgate & Vernetti 2014). Compared to a baseline period,
infants showed motor activation when an agent falsely believed a box contained a ball, but they
showed no motor activation when the agent falsely believed the box contained no ball. Infants
thus anticipated that the agent would search for the ball when she falsely believed it was present,
but not when she falsely believed it was absent.
Fifth, evidence of false-belief understanding has also been obtained with toddlers in the third
year of life (ages 2 to 3 years) using various spontaneous-response tasks (e.g., He et al. 2011,
2012; Scott et al. 2012). Importantly, some of these tasks have been highly verbal, with linguistic
demands comparable to those of elicited-prediction tasks (He et al. 2012, Scott et al. 2012). In one
violation-of-expectation task, for example, 2.5-year-olds watched a typical Sally-Anne scene along
with an adult “subject” who was then asked where Sally would look for her toy when she returned
(Scott et al. 2012). Children looked longer when the “subject” responded incorrectly and pointed
to the toy’s current as opposed to original location. Similarly, in a preferential-looking task, 2.5-
year-olds listened to a false-belief story, accompanied by a picture book, about a character named
Emily and her apple (Scott et al. 2012). In the final double-page of the book, one picture showed
Emily searching for her apple where she falsely believed it to be (original-location picture), and
the other picture showed Emily searching for her apple in its current location (current-location
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picture). Upon hearing the final line of the story, which stated that Emily was looking for her apple,
children looked preferentially at the original-location picture, suggesting that they represented
Emily’s false belief and understood how it would guide her actions. These results make clear that
the reason why young children fail at elicited-prediction tasks but succeed at spontaneous-response
tasks is not simply that the former are highly verbal whereas the latter are not; young children
succeed even at highly verbal spontaneous-response false-belief tasks.
Finally, positive results have been obtained using nonverbal and highly verbal spontaneous-
response false-belief tasks not only with young Western children, but also with 22- to 40-month-
old children from three traditional non-Western societies: a Salar community in northwest China,
a predominantly Shuar community in southeastern Ecuador, and a Yasawan community in north-
west Fiji (Barrett et al. 2013).
Elicited-Intervention False-Belief Tasks
In elicited-intervention false-belief tasks, infants are asked a test question, but this question does
not require them to predict the behavior of a mistaken agent. Instead, they are prompted to
perform an action such as retrieving or selecting an object for the agent; for infants to succeed,
their actions must be guided by an understanding of the agent’s false belief. In the helping task
of Buttelmann et al. (2009), an experimenter first showed 18-month-olds how to lock and unlock
two lidded boxes; the boxes were left unlocked. Next, a male agent entered the room, hid a toy
in one of the boxes, and then left. While he was gone, the experimenter moved the toy to the
other box and locked both boxes. When the agent returned, he tried to open the box where he
had hidden his toy, without success, and then sat centered behind the boxes. When prompted to
help the agent (“Go on, help him!”), most infants approached the box the agent had not acted on,
suggesting that they understood he wanted his toy and falsely believed it was still in its original
location (when the agent witnessed the toy’s transfer, infants inferred that he wanted to open the
empty box, and they approached that box instead).
In the referential-communication task of Southgate et al. (2010), 17-month-olds watched as an
agent hid two distinct objects in two lidded boxes and then left; in her absence, an experimenter
switched the objects. When the agent returned, she pointed to one of the boxes and said it contained
a “sefo.” The agent then opened the two boxes and asked infants, “Can you get the sefo for me?”
Most infants approached the box the agent had not pointed to, suggesting that they understood
the agent held a false belief about which object was in which box and intended to label the other
object as the sefo. Similar results were obtained when the agent simply pointed to one of the boxes,
said she wanted to play with the object in it, and asked the infants, “Can you get it for me?”
In addition to false beliefs about location, elicited-intervention tasks have been used to exam-
ine infants’ understanding of false beliefs about contents and identity (Buttelmann et al. 2014,
2015). In an unexpected-contents task (Buttelmann et al. 2014), 18-month-olds and an agent first
encountered three “block boxes” that each contained a block. Next, in the agent’s absence, infants
learned that a fourth block box actually contained a spoon. When the agent returned and reached
vainly for the fourth block box, infants were shown a block and a spoon and asked to give one
to the agent. Similarly, in a deceptive-identity task (Buttelmann et al. 2015), 18-month-olds and
an agent first encountered an object that appeared to be a toy duck. Next, in the agent’s absence,
infants learned that the object was actually a brush. When the agent returned and reached vainly
for the object, infants were shown a (nondeceptive) toy duck and a brush and asked to give one to
the agent. In each task, infants correctly selected the object that matched the agent’s false belief
(i.e., the block and the duck, respectively); this pattern reversed if the agent remained present
during the relevant demonstrations.
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HOW SHOULD EARLY PSYCHOLOGICAL REASONING
BE CHARACTERIZED?
We have argued, based on the findings presented in this review, that early psychological reasoning
is mentalistic: Infants attribute to agents motivational, epistemic, and counterfactual mental states,
and they use these mental states—together with the principle of rationality—to predict, interpret,
and evaluate agents’ actions and to guide their own actions toward the agents. Several alternative
interpretations have been offered for these findings.
Alternative Interpretations
According to some views, infants are not yet capable of genuine psychological reasoning. In
the low-level-process view, infants represent events in psychological-reasoning experiments “as
colours, shapes, and movements, rather than as actions on objects by agents” (Heyes 2014, p. 648),
and their responses are driven by perceptual novelty and other low-level domain-general processes.
In the behavioral-rule view, infants do perceive agents acting on objects, but their expectations
about agents are statistical rather than causal. In everyday life, infants gather information, in the
form of statistical regularities or behavioral rules, about how agents typically behave in specific situ-
ations (e.g., an agent will search for an object where it was last seen); infants then apply these rules to
interpret or predict agents’ actions (e.g., Perner 2010, Ruffman 2014). Given the wealth of findings
available today, these views seem unlikely. Infants’ psychological reasoning is highly context sen-
sitive, and a myriad of low-level processes or behavioral rules would be needed to explain all these
findings. It seems more plausible to grant infants an abstract capacity for making sense of agents’ ac-
tions (for further discussion, see Baillargeon et al. 2015, Carruthers 2013, Jacob 2015, Scott 2014).
According to the teleological view, young infants do engage in psychological reasoning and
abide by a principle of rationality, but their reasoning is at first nonmentalistic and reality based.
More specifically, (a) infants deal exclusively with physical variables such as situational constraints
and end-states (infants do not attribute goals to agents, but simply track the outcomes they achieve),
and (b) infants are egocentric and cannot entertain a representation of reality that is different from
their own (Gergely & Csibra 2003, Gergely et al. 1995). The recent evidence that even young
infants appreciate that an agent may be ignorant or mistaken about some aspect of a scene is
inconsistent with the teleological view, or at least suggests that psychological reasoning is already
mentalistic by the first half birthday.
According to the minimalist view, infants’ psychological-reasoning system is mentalistic from
the start, but the range of mental states it can handle is sharply limited. In particular, the system
cannot represent false beliefs and other counterfactual states, although it can track belief-like
states or “registrations” that are sufficient for success at many spontaneous-response and elicited-
intervention tasks (e.g., Apperly & Butterfill 2009, Butterfill & Apperly 2013). Upon encountering
an object, an agent registers its location and properties; by tracking this registration (even if its con-
tents become outdated), infants can predict the agent’s actions. For example, if an agent hides an
object in one location and in her absence the object is moved to another location, infants can antic-
ipate that the agent, upon returning to the scene, will search for the object where she last registered
it. According to the minimalist view, infants’ psychological-reasoning system presents a number
of “signature” limits, which include (a) an inability to represent false beliefs about identity (these
require taking into account not only what objects are registered but also how they are registered),
and (b) an inability to reason about a complex, interlocking set of mental states that interact causally
(e.g., Apperly & Butterfill 2009, Butterfill & Apperly 2013, Low et al. 2014, Low & Watts 2013).
However, there is reason to doubt both of these limits: Infants have now been found to attribute
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false beliefs about identity in several tasks, and success at these tasks typically requires reasoning
about an interlocking, causally coherent set of motivational, epistemic, and counterfactual states
(e.g., Buttelmann et al. 2015, Scott & Baillargeon 2009, Scott et al. 2015a, Song & Baillargeon
2008). For example, recent experiments examined whether 17-month-olds could reason about the
actions of a deceptive agent who sought to implant in another agent a false belief about the identity
of an object (Scott et al. 2015a). In each experiment, a thief attempted to secretly steal a desirable
rattling toy during its owner’s absence by substituting a less desirable silent toy. Infants realized
that this substitution could be effective only if the silent toy was visually identical to the rattling
toy and the owner did not routinely shake her toy when she returned; when these conditions were
met, infants expected the owner to be deceived and to mistake the silent toy for the rattling toy
she had left behind. These results suggest that infants in the second year of life can reason not
only about the actions of agents who hold false beliefs about identity, but also about the actions
of agents who seek to implant such false beliefs, providing strong support for the mentalistic view
that an abstract capacity to represent and reason about false beliefs is already present in infancy.
Implicit and Explicit Psychological Reasoning
What does implicit mean? Infants’ psychological reasoning is often characterized as implicit,
but different investigators mean different things by this term. One meaning (akin to sham) refers
to processes that mimic more advanced, explicit processes but do not, in fact, involve the same
concepts (e.g., if infants represented that “an object and another object” were in a box, they would
have only an implicit understanding of the concept “two,” as this concept would not figure in
any way in their reasoning). Another meaning of the term implicit (akin to unconscious) refers to
reasoning that occurs without explicit awareness of either the processes at work or the contents
they generate. Yet another meaning of the term implicit (akin to intuitive) refers to reasoning
that occurs without conscious awareness of the processes involved but can be accompanied by
awareness of the contents generated.
Given the evidence reviewed in this article, the intuitive meaning of the term implicit comes
closest to describing infants’ psychological reasoning. As Vierkant argued, it is unlikely that infants
in false-belief tasks who produce actions such as retrieving, selecting, and pointing to objects are
unaware of these actions: “There might well be some false-belief understanding that cannot yet be
deliberated about by a child, but which can nevertheless inform the fully consciously controlled
actions of that child. ... The child makes a conscious choice, and this choice turns out to be
an appropriate one, because it was influenced by the child’s false-belief understanding. ... The
behavior is not controlled by an unconscious zombie system ...but by a conscious agent” (Vierkant
2012, p. 154).
Explicit reasoning does not supplant intuitive reasoning. Like infants, older children and
adults routinely engage in intuitive reasoning about others’ actions (e.g., Brown-Schmidt et al.
2008, German & Cohen 2012, Kov´
acs et al. 2010, Senju et al. 2009); unlike infants, however, older
children and adults are also capable of explicit psychological reasoning. First, they can consciously
deliberate about others’ actions and verbalize their understanding of these actions (e.g., they can
explain that Sally will go to the basket because she thinks her marble is still there; Amsterlaw &
Wellman 2006, Bartsch & Wellman 1989). Second, they develop a folk theory of psychology (just
as they develop folk theories of astronomy and biology; e.g., Carey 1985, Vosniadou & Brewer
1992), which enables them to think and talk about theoretical concepts such as false beliefs (e.g.,
Gopnik & Wellman 1994, Leslie 2000).
There is currently a heated debate about how explicit psychological reasoning develops, how it
relates to implicit psychological reasoning (in children and in adults), and whether its emergence is
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what makes possible children’s success at elicited-prediction false-belief tasks (e.g., when a 4-year-
old points to the correct location in such a task, this action is certainly consciously controlled, but
does it necessarily reflect an explicit reasoning process?). These issues represent the new frontier
in the research on early psychological reasoning, and findings from behavioral and neuroscientific
methods are producing new insights (e.g., Hyde et al. 2015, Kov´
acs et al. 2014a). One other
approach is also yielding thought-provoking results: Over the past few years, researchers have
begun to conduct longitudinal studies exploring the continuity of psychological reasoning from
infancy to childhood (e.g., Aschersleben et al. 2008, Thoermer et al. 2012, Wellman et al. 2008,
Yamaguchi et al. 2009). Although results have been somewhat variable due to small samples,
several studies have reported significant correlations involving false-belief understanding. In a
recent study, for example, performance in an anticipatory-looking task at age 18 months predicted
performance in various elicited-prediction tasks at 50 months (Sodian et al. 2015). These results
not only point to substantial continuity in early psychological reasoning, but also raise important
questions about individual differences and the factors responsible for them.
Finally, in light of the preceding discussion, it may be clearer why in this review we chose to
refer to infants’ ability to infer others’ mental states as “psychological reasoning” rather than as
“theory of mind,” as is often the case. We prefer the term psychological reasoning for two reasons
(see also Schaafsma et al. 2015). First, this term underscores the deep similarities between infants’
psychological reasoning and their reasoning in other core domains of causal reasoning, such as
physical and sociomoral reasoning (e.g., Baillargeon et al. 2013, 2015). Second, the term theory
of mind sometimes fosters the assumption that the acquisition of a folk theory of psychology is
the primary endpoint of development in this domain and allows an explicit form of reasoning
to supplant a more intuitive form of reasoning. As we have just seen, intuitive psychological
reasoning persists throughout life, and its relation to explicit psychological reasoning is far from
being completely understood.
CONCLUSION
The extensive evidence reviewed in this article indicates that from a very early age, psychological
reasoning is mentalistic in nature. Upon observing an agent act in a scene, infants attempt to infer
the agent’s motivational, epistemic, and counterfactual states; infants then use these mental states,
together with the principle of rationality, to predict and interpret the agent’s subsequent actions
and to guide their own actions toward the agent. Much remains to be discovered about how infants’
ability to infer and reason about others’ mental states improves with age, about the maturation
of the brain networks that underlie this ability, and about the various factors that contribute to
individual differences in neurotypical and other populations. Nevertheless, it seems clear that this
core domain of causal reasoning depends on a content-rich, adaptive, neurocomputational system
that begins to operate early in life (Cosmides & Tooby 2013).
DISCLOSURE STATEMENT
The authors are not aware of any affiliations, memberships, funding, or financial holdings that
might be perceived as affecting the objectivity of this review.
ACKNOWLEDGMENTS
We wish to thank Shelley Taylor and Lisa Dean for their suggestions, support, and patience, as
well as Andrei Cimpian, Melody Buyukozer Dawkins, Cynthia Fisher, Gerald DeJong, Francesco
Margoni, and Francisca Ting for helpful comments.
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PS67-FrontMatter ARI 23 November 2015 19:6
Annual Review of
Psychology
Volume 67, 2016
Contents
In Pursuit of Three Theories: Authoritarianism, Relative Deprivation,
and Intergroup Contact
Thomas F. Pettigrew ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp1
Drug Addiction: Updating Actions to Habits to Compulsions
Ten Years On
Barry J. Everitt and Trevor W. Robbins ppppppppppppppppppppppppppppppppppppppppppppppppppppp23
Remembering Preservation in Hippocampal Amnesia
Ian A. Clark and Eleanor A. Maguire ppppppppppppppppppppppppppppppppppppppppppppppppppppppp51
Beyond Words: How Humans Communicate Through Sound
Nina Kraus and Jessica Slater pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp83
Episodic Memory and Beyond: The Hippocampus and Neocortex
in Transformation
Morris Moscovitch, Roberto Cabeza, Gordon Winocur, and Lynn Nadel pppppppppppppppp105
Counterfactual Thought
Ruth M.J. Byrne pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp135
Psychological Reasoning in Infancy
Ren´ee Baillargeon, Rose M. Scott, and Lin Bian ppppppppppppppppppppppppppppppppppppppppppp159
Socioemotional, Personality, and Biological Development: Illustrations
from a Multilevel Developmental Psychopathology Perspective
on Child Maltreatment
Dante Cicchetti pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp187
The Affective Neuroscience of Aging
Mara Mather pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp213
Gene ×Environment Determinants of Stress- and Anxiety-Related
Disorders
Sumeet Sharma, Abigail Powers, Bekh Bradley, and Kerry J. Ressler ppppppppppppppppppp239
Automaticity: Componential, Causal, and Mechanistic Explanations
Agnes Moors ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp263
Psychology of Habit
Wendy Wood and Dennis R¨unger pppppppppppppppppppppppppppppppppppppppppppppppppppppppppp289
Media Effects: Theory and Research
Patti M. Valkenburg, Jochen Peter, and Joseph B. Walther pppppppppppppppppppppppppppppp315
vi
Annu. Rev. Psychol. 2016.67:159-186. Downloaded from www.annualreviews.org
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PS67-FrontMatter ARI 23 November 2015 19:6
Changing Norms to Change Behavior
Dale T. Miller and Deborah A. Prentice ppppppppppppppppppppppppppppppppppppppppppppppppppp339
Consistency Versus Licensing Effects of Past Moral Behavior
Elizabeth Mullen and Benoˆıt Monin ppppppppppppppppppppppppppppppppppppppppppppppppppppppp363
Justice and Negotiation
Daniel Druckman and Lynn M. Wagner pppppppppppppppppppppppppppppppppppppppppppppppppp387
Stereotype Threat
Steven J. Spencer, Christine Logel, and Paul G. Davies pppppppppppppppppppppppppppppppppp415
Toward a Social Psychology of Race and Race Relations for the
Twenty-First Century
Jennifer A. Richeson and Samuel R. Sommers ppppppppppppppppppppppppppppppppppppppppppppp439
Theodiversity
Ara Norenzayan ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp465
Materialistic Values and Goals
Tim Kasser ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp489
Beyond Work-Life “Integration”
Joan C. Williams, Jennifer L. Berdahl, and Joseph A. Vandello ppppppppppppppppppppppppp515
Vocational Psychology: Agency, Equity, and Well-Being
Steven D. Brown and Robert W. Lent ppppppppppppppppppppppppppppppppppppppppppppppppppppp541
Causal Inference in Developmental Origins of Health and Disease
(DOHaD) Research
Suzanne H. Gage, Marcus R. Munaf`o, and George Davey Smith ppppppppppppppppppppppp567
From Brain Maps to Cognitive Ontologies: Informatics and the Search
for Mental Structure
Russell A. Poldrack and Tal Yarkoni ppppppppppppppppppppppppppppppppppppppppppppppppppppppp587
Modular Brain Networks
Olaf Sporns and Richard F. Betzel ppppppppppppppppppppppppppppppppppppppppppppppppppppppppp613
Sequential Sampling Models in Cognitive Neuroscience: Advantages,
Applications, and Extensions
B.U. Forstmann, R. Ratcliff, and E.-J. Wagenmakers ppppppppppppppppppppppppppppppppppp641
Evidence-Based Practice: The Psychology of EBP Implementation
Denise M. Rousseau and Brian C. Gunia pppppppppppppppppppppppppppppppppppppppppppppppppp667
Scientific Misconduct
Charles Gross pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp693
The Council of Psychological Advisers
Cass R. Sunstein ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp713
Contents vii
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Annual Review of Vision Science
vision.annualreviews.org • Volume 1 • November 2015
Co-Editors: J. Anthony Movshon, New York University and Brian A. Wandell, Stanford University
The Annual Review of Vision Science reviews progress in the visual sciences, a cross-cutting set of disciplines that intersect
psychology, neuroscience, computer science, cell biology and genetics, and clinical medicine. The journal covers a broad
range of topics and techniques, including optics, retina, central visual processing, visual perception, eye movements, visual
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TABLE OF CONTENTS FOR VOLUME 1:
Adaptive Optics Ophthalmoscopy, Austin Roorda,
Jacque L. Duncan
Angiogenesis in Eye Disease, Yoshihiko Usui,
Peter D. Westenskow, Salome Murinello, Michael I. Dorrell,
Leah Scheppke, Felicitas Bucher, Susumu Sakimoto,
Liliana P Paris, Edith Aguilar, Martin Friedlander
Color and the Cone Mosaic, David H. Brainard
Control and Functions of Fixational Eye Movements,
Michele Rucci, Martina Poletti
Deep Neural Networks A New Framework for Modeling
Biological Vision and Brain Information Processing,
Nikolaus Kriegeskorte
Development of Three-Dimensional Perception in Human
Infants, Anthony M. Norcia, Holly E. Gerhard
Functional Circuitry of the Retina, Jonathan B. Demb,
Joshua H. Singer
Image Formation in the Living Human Eye, Pablo Artal
Imaging Glaucoma, Donald C. Hood
Mitochondria and Optic Neuropathy, Janey L. Wiggs
Neuronal Mechanisms of Visual Attention, John Maunsell
Optogenetic Approaches to Restoring Vision, Zhuo-Hua
Pan, Qi Lu, Anding Bi, Alexander M. Dizhoor, Gary W. Abrams
Organization of the Central Visual Pathways Following Field
Defects Arising from Congenital, Inherited, and Acquired
Eye Disease, Antony B. Morland
Contributions of Retinal Ganglion Cells to Subcortical
Visual Processing and Behaviors, Onkar S. Dhande,
Benjamin K. Staord, Jung-Hwan A. Lim,
Andrew D. Huberman
Ribbon Synapses and Visual Processing in the Retina,
Leon Lagnado, Frank Schmitz
The Determination of Rod and Cone Photoreceptor Fate,
Constance L. Cepko
A Revised Neural Framework for Face Processing,
Brad Duchaine, Galit Yovel
Visual Adaptation, Michael A. Webster
Visual Functions of the Thalamus, W. Martin Usrey,
Henry J. Alitto
Visual Guidance of Smooth Pursuit Eye Movements,
Stephen Lisberger
Visuomotor Functions in the Frontal Lobe, Jerey D. Schall
What Does Genetics Tell Us About Age-Related
Macular Degeneration? Felix Grassmann, Thomas Ach,
Caroline Brandl, Iris M. Heid, Bernhard H.F. Weber
Zebrash Models of Retinal Disease, Brian A. Link,
Ross F. Collery
Access all Annual Reviews journals via your institution at www.annualreviews.org.
FREE online access to Volume 1 will be available until November 2016.
Annu. Rev. Psychol. 2016.67:159-186. Downloaded from www.annualreviews.org
Access provided by University of Illinois - Urbana Champaign on 08/18/16. For personal use only.
... Al respecto, los estudios que han utilizado una versión explícita-verbal de la tarea de la falsa creencia han reportado una secuencia de desarrollo de la capacidad para razonar sobre los estados mentales de los demás a partir de los cuatro años, pero no antes (Wellman, 2014;Wellman et al., 2001;Wimmer & Perner, 1983). Sin embargo, estudios recientes que han implementado una versión implícita-no verbal de la tarea han mostrado que los niños pequeños (M < 2 años) con un DT tienen la capacidad de anticiparse correctamente a las acciones de un agente sobre la ubicación o identidad de un objeto basándose en la atribución de una falsa creencia (Baillargeon et al., , 2016Buttelmann & Kovács, 2019;Onishi & Baillargeon, 2005;Scott et al., 2010;Siu & Cheung, 2019). ...
... Por otro lado, los estudios sobre el desarrollo de la TdM han señalado que los niños neurotípicos adquieren la capacidad para comprender explícitamente las creencias falsas alrededor de los 4 años (Oktay-Gür et al., 2018;Wellman, 2014;Wellman et al., 2001;Wimmer & Perner, 1983). Sin embargo, también se ha demostrado que los bebés desde los 15 meses dominan las tareas no verbales de la falsa creencia (Baillargeon et al., , 2016Onishi & Baillargeon, 2005;, lo que se ha interpretado a favor de la idea de que tienen una TdM implícita que les permite reconocer que las acciones de los demás están orientadas intencionalmente o dirigidas a objetivos (Baillargeon et al., 2016;Buttelmann & Kovács, 2019). ...
... Por otro lado, los estudios sobre el desarrollo de la TdM han señalado que los niños neurotípicos adquieren la capacidad para comprender explícitamente las creencias falsas alrededor de los 4 años (Oktay-Gür et al., 2018;Wellman, 2014;Wellman et al., 2001;Wimmer & Perner, 1983). Sin embargo, también se ha demostrado que los bebés desde los 15 meses dominan las tareas no verbales de la falsa creencia (Baillargeon et al., , 2016Onishi & Baillargeon, 2005;, lo que se ha interpretado a favor de la idea de que tienen una TdM implícita que les permite reconocer que las acciones de los demás están orientadas intencionalmente o dirigidas a objetivos (Baillargeon et al., 2016;Buttelmann & Kovács, 2019). ...
Article
Association between executive functions and theory of mind in children: Empirical evidence and theoretical implications. Previous studies have found that executive functioning (EF) is related to theory of mind (ToM). However, the directionality and strength of this link remain a topic of debate in the current literature. The aim of this paper was to analyze the study perspectives and empirical evidence on the directionality and strength of the co-development of EF and ToM in children. The literature search was performed in Web of Science. Sci2 Tool and Gephi were used for the analysis. Cluster analysis showed three study perspectives focused on the relationship between EF performance and ToM in children with attention deficit hyperactivity disorder (ADHD) (1), autism spectrum disorder (ASD) (2) and typical development (TD) (3). We found a consistent pattern of association between EF and ToM in children with ASD, ADHD, and TD. Longitudinal findings showed that the association between early EF and late ToM, including false belief comprehension, is stronger than the inverse association and tends to consolidate with age, indicating an EF→ToM, but not ToM→EF directionality, and is not better explained by the effect of executive demands posed in ToM tasks. Taken together, the evidence supports the “emergence” and “enrichment” theoretical accounts in considering that EFs in early child neurodevelopment are ontogenetically implicated in the acquisition, consolidation, and change of psychological state comprehension abilities in others
... Examples of updated methodology can be found in Wang, rarer, whilst implicit testing has flourished. Reviews by Baillargeon et al. (2015), and Baillargeon, Scott and Bian (2016), describe dozens of tests purporting to demonstrate that infants have surprisingly flexible false belief reasoning skills. ...
... Putting positions on concepts and cognitive architectures together, we see that, for example, Heyes (2014) takes a heavily constructivist and non-modular approach (to learning, at least), arguing that behavioural reasoning and heuristics explain away the nativist-coded implicit testing data. Alternatively, Baillargeon, Scott, and Bian (2016), and Carruthers' (2013) nativist and modular approach maintains that the puzzle of mindreading is accounted for by cognitive bottlenecks that prevent infants from applying (through language) their already latent concepts of belief. Furthermore, Apperly and Butterfill (2009), and Butterfill and Apperly (2013), also held that children reason through false-belief tasks using mental concepts and not merely by parsing behaviour, but they maintain that the mindreading module is split in two. ...
Thesis
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We make character trait attributions to predict and explain others’ behaviour. How should we understand character trait attribution in context across the domains of philosophy, folk psychology, developmental psychology, and evolutionary psychology? For example, how does trait attribution relate to our ability to attribute mental states to others, to ‘mindread’? This thesis uses philosophical methods and empirical data to argue for character trait attribution as a practice dependent upon our ability to mindread, which develops as a product of natural selection acting on culture instead of genes. This analysis carves out trait attribution’s distinct place within an emerging complex and mature scholarship on pluralistic social cognition.
... The same principle of rationality that keeps infants from predicting a specific choice after the one-object condition, should keep them from making a specific prediction after the differentpositions condition, because no information about a preference is given in this case either. 76 The pairing hypothesis does not have this problem. It explains the different-positions condition by emphasizing the behavioral variability that infants experience in themselves and in the caregivers they soon become familiar with. ...
Article
Full-text available
A deep and polarizing tension in cognitive science is the one between cognitivism and the 4E Cognition approach. A lack of serious engagement with the theoretical and empirical work generated in the opposite framework seems problematic on both sides. In this paper, we closely discuss data on early socio-cognitive development produced by an influential nativist current of the cognitivist paradigm. We consider these data from the point of view of a 4E Cognition perspective called “the pairing hypothesis,” which originates in phenomenological philosophy. We show that a close examination of cognitivist-nativist data strengthens this phenomenological 4E Cognition perspective by significantly expanding the range of findings it can account for. By addressing the debate between rich and lean explanations in early social cognition, we corroborate the idea that a careful interaction between cognitivism and the 4E Cognition approach can be a fruitful way to make progress in cognitive science.
... Infants even differentiate moving animations as "agents" and "patients" based on motion direction (13), consistent with Michotte's (22) findings that people easily attribute causality even to simple action sequences. Indeed, evidence suggests that infants can identify an agent if it exhibits internal control over its actions (128). Seven-month-old children form different expectations about movement by animate and inanimate agents (129): In these scenarios, people changed their motion, either after coming into contact with another object (or person) or after stopping short of that contact. ...
Article
Languages tend to encode events from the perspective of agents, placing them first and in simpler forms than patients. This agent bias is mirrored by cognition: Agents are more quickly recognized than patients and generally attract more attention. This leads to the hypothesis that key aspects of language structure are fundamentally rooted in a cognition that decomposes events into agents, actions, and patients, privileging agents. Although this type of event representation is almost certainly universal across languages, it remains unclear whether the underlying cognition is uniquely human or more widespread in animals. Here, we review a range of evidence from primates and other animals, which suggests that agent-based event decomposition is phylogenetically older than humans. We propose a research program to test this hypothesis in great apes and human infants, with the goal to resolve one of the major questions in the evolution of language, the origins of syntax.
... Several scientists argue that morality does not necessarily imply fairness and may include a greater variety of actions (Haidt, 2007;Haidt & Graham, 2007;Haidt et al., 1993). Other researchers claim that early socio-moral reasoning is guided by some concepts and principles that are early and universally in development, normative in nature and interacting when they apply in the same situation (Baillargeon et al., 2016;Baumard et al., 2013;Dupoux & Jacob, 2007;Graham et al., 2013;Rai & Fiske, 2011;. Others support that young children by 3-4 years of age understand that moral concepts are generalizable, reflecting concerns for fairness, equality and rights (Killen & Smetana, 2015;Smetana et al., 2012), and applied to a societal domain based on ingroup membership (concerning ingroup-norms, group identity and group dynamics) (Cooley & Killen, 2015;Rutland & Killen, 2017). ...
Article
Full-text available
The principle of fairness is very important in social life and plays an important role in socio-moral evaluation; in the last decade, the amount of research on this topic is increasing and suggests different considerations about its origin whether this principle is present at birth or constructed later in development. This article presents some of these considerations focused on the common aspects of innatist and constructivist views and sheds light on the role of experience. The conclusions suggest a more integrated approach, supporting that experience seems to instantiate and model an abstract representation that can be presumably innate. The pursuit of this approach could help researchers to address questions in the field.
... Humans have a penchant for taking an intentional stance (Dennett, 1989). Even young infants expect agents to act intentionality towards their goals through the principle of rationalityagents will act consistently and efficiently in relation to their goals, desires, and beliefs (Baillargeon et al., 2016). For instance, 6-month-old infants expect that a consistently repeated object selection is intentional and indicates a preference for that object (Woodward, 1998) and that agents will use the most © 2022 Informa UK Limited, trading as Taylor & Francis Group CONTACT Lukas D. Lopez llopez65@ucmerced.edu ...
Article
Infants use statistical information in their environment, as well as others' emotional communication, to understand the intentions of social partners. However, rarely do researchers consider these two sources of social information in tandem. This study assessed 2-year-olds' attributions of intentionality from non-random sampling events and subsequent discrete emotion reactions. Infants observed an experimenter remove five objects from either the non-random minority (18%) or random majority (82%) of a sample and express either joy, disgust, or sadness after each selection. Two-year-olds inferred the experimenter's intentionality by giving her the object that she had previously selected when she expressed joy or disgust after non-random sampling events, but not when she expressed sadness or sampled at random. These findings demonstrate that infants use both statistical regularities and discrete emotion communication to infer an agent's intentions. In particular, the present findings show that 2-year-olds infer that an agent can intentionally select a preferred or an undesired object from a sample as a function of the discrete emotion. Implications for the development of inferring intentionality from statistical sampling events and discrete emotion communication are discussed.
Article
There is considerable variability in the social categories that children essentialize and the types of expectations children form about these categories, suggesting children's essentialist beliefs are shaped by environmental input. Prior studies have shown that exposure to generic statements about a social category promotes essentialist beliefs in 4.5- to 8-year-old children. However, by this age children form essentialist beliefs quite robustly, and thus it is unclear whether generic statements impact children's expectations about social categories at younger ages when essentialist beliefs first begin to emerge. Moreover, in prior studies the generic statements were delivered by an experimenter and carefully controlled, and thus it is unclear whether these statements would have the same impact if they occurred in a somewhat less constrained setting, such as parents reading a picture book to their child. The current study addressed these open questions by investigating whether generic statements delivered during a picture-book interaction with their parents influenced 3-year-olds' expectations about members of a novel social category. Our results showed that children who heard generic statements during the picture-book interaction used social-group membership to make inferences about the likely behavior of a novel category member, whereas children who were not exposed to generic statements did not. These findings suggest that as early as 3 years of age, children's expectations about social categories are influenced by generic statements that occur during brief parent-child interactions.
Article
This study examined how the reliability (i.e., transitivity) of an agent’s object choices affects 16-month-old infants’ (N = 48) imitation of her unconventional way of turning on a touch light box with her head when her hands were available. When the agent made transitive choices (i.e., she chose Object A over Object B, Object B over Object C, and then A over C), infants imitated her head touch actions. When the agent made intransitive choices (i.e., after choosing A over B and B over C, she chose C over A), infants were more likely to use only their hands to touch the light box. In addition, when it was presumably difficult for infants to judge the transitivity of the agent’s choices (i.e., she chose B over C, A over B, and then A over C), they used their hands more. These results demonstrate that infants’ understanding informs their decisions to selectively imitate others’ specific ways to act on novel artifacts, consistent with young children’s selective trust in information provided by other people based on their epistemic reliability.
Article
Full-text available
Previous studies suggest that people from the Western hemisphere tend to explain others’ behavior based on a person’s traits and dispositions, while participants from non-Western cultural settings more likely refer to situational factors. From a developmental perspective, it has been suggested that culture-specific modes of explaining behavior gradually emerge during late childhood and adolescence. The present study explored whether traces of a corresponding culture-specific development can be found at earlier ages when using simplified assessments. In total, 438 children between 4 and 9 years old from Münster (urban Germany), Kyoto (urban Japan), and Cotacachi (rural Ecuador), were asked to explain positive and deviant behaviors of children depicted in simple picture-based vignettes. While more internal attributions were given in Münster than in Kyoto and Cotacachi children at 4 to 5 years old, these cultural differences disappeared as internal attributions significantly increased with age in Kyoto and Cotacachi but not Münster children. Analyzing children’s explanations on a level of subcategories revealed more subtle cultural specificities. For example, when giving internal explanations, Cotacachi children focused on stable traits, while Münster children emphasized individual desires and Kyoto children highlighted more volatile aspects. Cross-cultural differences in children’s social explanations could partially be explained by mothers’ preference for autonomy-related socialization goals. Taken together, this study provides evidence for an earlier onset of internal explanations when they are culturally accentuated and further calls for a more nuanced approach to capture culture-specific meaning systems reflected in everyday social explanations.
Article
To successfully navigate their social world, humans need to understand and map enduring relationships between people: Humans need a concept of social affiliation. Here I propose that the initial concept of social affiliation, available in infancy, is based on the extent to which one individual consistently takes on the goals and needs of another. This proposal grounds affiliation in intuitive psychology, as formalized in the naive-utility-calculus model. A concept of affiliation based on interpersonal utility adoption can account for findings from studies of infants' reasoning about imitation, similarity, helpful and fair individuals, "ritual" behaviors, and social groups without the need for additional innate mechanisms such as a coalitional psychology, moral sense, or general preference for similar others. I identify further tests of this proposal and also discuss how it is likely to be relevant to social reasoning and learning across the life span.
Article
Full-text available
Until recently, it was generally assumed that the ability to attribute false beliefs did not emerge until about 4 years of age. However, recent reports using spontaneous- as opposed to elicited-response tasks have suggested that this ability may be present much earlier. To date, researchers have employed two kinds of spontaneous-response false-belief tasks: violation-of-expectation tasks have been used with infants in the second year of life, and anticipatory-looking tasks have been used with toddlers in the third year of life. In the present research, 2.5-year-old toddlers were tested in violation-of-expectation tasks involving a change-of-location situation (Experiment 1) and an unexpected-contents situation (Experiment 2). Results were positive in both situations, providing the first demonstrations of false-belief understanding in toddlers using violation-of-expectation tasks and, as such, pointing to a consistent and continuous picture of early false-belief understanding.
Chapter
Considers various versions of what might be meant by saying that possession of a concept depends upon possessing knowledge of a theory. Specifically, the chapter considers the early appearing and highly abstract concept of BELIEF.
Article
Developmental psychology currently faces a deep puzzle: most children before 4 years of age fail elicited-response false-belief tasks, but preverbal infants demonstrate spontaneous false-belief understanding. Two main strategies are available: cultural constructivism and early-belief understanding. The latter view (unlike the former) assumes that failure at elicited-response false-belief tasks need not reflect the inability to understand false beliefs. The burden of early-belief understanding is to explain why elicited-response false-belief tasks are so challenging for most children under 4 years of age. The goal of this article is to offer a pragmatic framework whose purpose is to discharge this burden.
Chapter
Researchers disagree over whether preverbal infants have any true understanding of other minds. There seem to be at least two sources of hesitation among researchers. Some doubt that infants have any concepts as sophisticated as that implied by the term 'intentionality'. Other researchers simply doubt that infants understand anything in a conceptual way. This chapter provides arguments in favour of infants' abilities in both respects. It describes data from one study in which the method itself was designed to assess conceptual representations abstracted away from perception-action systems.
Article
Humans have the unique capacity to actively reflect on the thoughts, beliefs, and knowledge of others, but do we also track mental states spontaneously when observing other people? We asked this question by monitoring brain activity in belief-sensitive cortex using functional near-infrared spectroscopy (fNIRS) during free-viewing of social videos. More specifically, we identified a portion of the right temporal-parietal junction (rTPJ) selective for mental state processing using an established, explicit theory of mind task, and then analyzed the brain response in that region of interest (ROI) during free-viewing of video clips involving people producing goal-directed actions. We found a significant increase in oxygenated hemoglobin concentration in our rTPJ ROI during free-viewing for all of our test videos. Activity in this region was further modulated by the extent to which the knowledge state, or beliefs, of the protagonist regarding the location of an object contrasted with the reality of where the object was hidden. Open-ended questioning suggested our participants were not explicitly focusing on belief states of the characters during free-viewing. Further analyses ruled out lower-level details of the video clips or general attentional differences between conditions as likely explanations for the results. As such, these results call into question the traditional characterization of theory of mind as a resource intensive, deliberate process, and, instead, support an emerging view of theory of mind as a foundation for, rather than the pinnacle of, human social cognition. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.