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Future thinking in animals: Capacities and limits

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Abstract

The previous two decades have seen much theoretical and empirical research into the future thinking capacities of non-human animals. Here we critically review the evidence across six domains: (1) navigation and route planning, (2) intertemporal choice and delayed gratification, (3) preparing for future threats, (4) acquiring and constructing tools to solve future problems, (5) acquiring, saving and exchanging tokens for future rewards, and (6) acting with future desires in mind. In each domain we show that animals are capable of considerably more sophisticated future-oriented behavior than was once thought possible. Explanations for these behaviors remain contentious, yet in some cases it may be most parsimonious to attribute animals with mental representations that go beyond the here-and-now. Nevertheless, we also make the case that animals may not be able to represent future representations as future representations – an overarching capacity that allows humans to reflect on their own natural future thinking limits and act to compensate for these limits. Throughout our analysis we make specific suggestions for how future research can continue to make progress on this and other important questions in the field.
Running head: FUTURE THINKING IN ANIMALS 1
Future Thinking in Animals: Capacities and Limits
Jonathan Redshaw, University of Queensland
Adam Bulley, University of Queensland
Author Note
Jonathan Redshaw, School of Psychology, University of Queensland, St Lucia, QLD,
4072, Australia
Adam Bulley, School of Psychology, University of Queensland, St Lucia, QLD, 4072,
Australia
Chapter to appear in: Oettingen, G., Sevincer, A. T., & Gollwitzer, P. M. (2017). The
psychology of thinking about the future. New York: Guilford.
Address of Correspondence: Jonathan Redshaw, School of Psychology, University of
Queensland, St Lucia, QLD, 4072, Australia. e-mail: j.redshaw@uq.edu.au
Running head: FUTURE THINKING IN ANIMALS 2
Abstract
The previous two decades have seen much theoretical and empirical research into the future
thinking capacities of non-human animals. Here we critically review the evidence across six
domains: (1) navigation and route planning, (2) intertemporal choice and delayed
gratification, (3) preparing for future threats, (4) acquiring and constructing tools to solve
future problems, (5) acquiring, saving and exchanging tokens for future rewards, and (6)
acting with future desires in mind. In each domain we show that animals are capable of
considerably more sophisticated future-oriented behavior than was once thought possible.
Explanations for these behaviors remain contentious, yet in some cases it may be most
parsimonious to attribute animals with mental representations that go beyond the here-and-
now. Nevertheless, we also make the case that animals may not be able to represent future
representations as future representations – an overarching capacity that allows humans to
reflect on their own natural future thinking limits and act to compensate for these limits.
Throughout our analysis we make specific suggestions for how future research can continue
to make progress on this and other important questions in the field.
Running head: FUTURE THINKING IN ANIMALS 3
Future Thinking in Animals: Capacities and Limits
The brute is an embodiment of present impulses, and hence what elements of fear and
hope exist in its nature – and they do not go very far – arise only in relation to objects
that lie before it and within reach of those impulses; whereas a man’s range of vision
embraces the whole of his life, and extends far into the past and future.
– Arthur Schopenhauer, Studies in Pessimism, 1851
Non-human animals1 do not harness the future to dominate their environments in the
immediately obvious way that humans do (Suddendorf, 2006). It is therefore unsurprising
that early thinkers such as Schopenhauer and others (e.g., Bergson, 1896/2004; Köhler,
1917/1927; Nietzsche, 1876/1998) regarded animals as being largely mentally bound to the
present (but see James, 1890). Contemporary scientific theorists have also made cases for
strong limits on non-human future thinking (Roberts, 2002; Suddendorf & Corballis, 1997),
and driven by these claims comparative psychologists have begun to document animal
behaviors that appear in some way oriented towards the future (for previous reviews, see
Cheke & Clayton, 2010; Roberts, 2012; Suddendorf & Corballis, 2007, 2010). Conflicting
interpretations of the results has led to the formation of two camps within the literature: one
that tends to emphasize the possible continuities between human and animal future thinking
(e.g., Clayton, Bussey, & Dickinson, 2003; Corballis, 2013; Osvath & Martin-Ordas, 2014;
Roberts, 2012; Scarf, Smith, & Stuart, 2014; Zentall, 2005), and one that tends to emphasize
the possible discontinuities (e.g., Cheng, Werning, & Suddendorf, 2016; Hoerl, 2008;
Redshaw, 2014; Suddendorf, 2013a; Tulving, 2005).
Despite much heated debate, however, the dichotomy between the continuity and
discontinuity camps is in many respects a false one. Both sides would agree, for instance, that
animals often act in ways that increase their future survival and/or reproductive chances
1 Hereafter ‘animals’
Running head: FUTURE THINKING IN ANIMALS 4
without mentally representing the future at all. Future-oriented behaviors need not necessarily
require sophisticated planning, but instead can exist as purely innate processes (e.g., fixed
action patterns) and/or arise via associative learning (Suddendorf & Corballis, 2007, 2010).
Both sides would also agree that future thinking is not an all-or-none process; an
encapsulated cognitive module that an organism is either equipped with or not. Among
humans, the various components involved in future thinking come online at different ages
during childhood (Suddendorf & Redshaw, 2013), and individual differences in the capacity
persist into adulthood (e.g., Lebreton et al., 2013). Finally, both sides of the debate would
agree that: (1) at least some animals can represent more than just perceptual information tied
to the present, and (2) there are at least some differences between human and animal future
thinking (whether these differences be quantitative or qualitative in nature).
In defining future thinking, various theoretical positions have placed differential
emphasis on the subjective nature of the phenomenon and its behavioral consequences.
Tulving (1985), for instance, initially put forward the notion of autonoetic or ‘self-knowing’
consciousness to refer to the first-person awareness often implicated in mental access to past
and future autobiographical events. Suddendorf and Corballis (1997) later coined the term
mental time travel to refer to these declarative mental trips into past and future, and also
indicated that important differences may exist between the capacities of humans and animals.
Specifically, they proposed the seminal Bischof-Köhler hypothesis (cf. Bischof-Köhler, 1985;
Bischof, 1985; Köhler, 1917/1927), suggesting that animals may not be able to imagine and
prepare for future desire states that conflict with their current state (see the section ‘Acting
with future desires in mind’). Subsequently, however, Suddendorf and Corballis (2007; 2010)
emphasized how the behavioral consequences of this future thinking might be discerned,
reasoning that evolution can work only on the behavioral ‘output’ or actions of an animal,
and not on mental events per se. A number of researchers have since proposed that certain
Running head: FUTURE THINKING IN ANIMALS 5
behavioral capacities (Raby & Clayton, 2009) or underlying mechanisms (Osvath, 2016;
Osvath & Martin-Ordas, 2014) should be key to understanding the future thinking of animals.
The empirical goal of comparative psychologists, then, should perhaps not be to determine
whether animals can mentally represent events that have not yet happened, but rather to
establish their capacities and limits in various future-oriented behavioral domains (Osvath,
2016; Raby & Clayton, 2009; Suddendorf & Corballis, 2007).
In the bulk of this chapter we review and critique the evidence for future-oriented
animal behavior from several lines of research. Future thinking itself, of course, cannot be
directly observed in non-verbal subjects, yet with careful controls simpler alternative
explanations for their behavior can be ruled out with increasing confidence (Suddendorf &
Corballis, 2010). Throughout our analysis we highlight not only the achievements of animals
on certain tasks, but also their failures and suggest where their cognitive limits may lie. We
then synthesize these findings and make the case for at least one overarching limit – namely,
that animals (unlike humans) may not be able to reflect on their own natural future thinking
limitations and act to compensate for them to acquire additional benefits. Given that the vast
majority of research has focused on primates, rodents, or corvids, we largely restrict our
analysis to studies of these taxa. We do, however, point towards other branches of the
phylogenetic tree that may be worth investigating.
Animal Future Thinking Across Domains
In the following sections we survey the behavioral evidence for animal future thinking
across six domains: (1) navigation and route planning, (2) intertemporal choice and delayed
gratification, (3) preparing for future threats, (4) acquiring and constructing tools to solve
future problems, (5) acquiring, saving, and exchanging tokens for future rewards, and (6)
acting with future desires in mind. We then summarize animals’ capacities and potential
limits in each domain in Table 1.
Running head: FUTURE THINKING IN ANIMALS 6
Navigation and Route Planning
It is not surprising that many animals should possess mental representations of their
environments in order to navigate through them safely and efficiently. Indeed, classic
behavioral research demonstrates that rodents (O'Keefe & Nadel, 1978; Tolman, 1948),
chimpanzees (Boesch & Boesch, 1984; Menzel, 1973) and perhaps even bees (Gould, 1986)
rely on ‘cognitive maps’ to pursue both familiar and novel paths through known
environments in order to attain rewards and avoid threats. Interestingly, recent research
suggests that rodents may mentally pre-experience such routes before they pursue them, both
inside and outside of the simulated spatial context. This inference is based on recordings from
hippocampal place cells, which show similar patterns of firing before the rodents take a path
and then when they actually take the path (see, e.g., Dragoi & Tonegawa, 2013; Ólafsdóttir,
Barry, Saleem, Hassabis, & Spiers, 2015; Pfeiffer & Foster, 2013).
If we grant the validity of hippocampal place cell recordings as evidence of
phenomenological experience (cf. Suddendorf, 2013a), then the data do indeed suggest that
rodents mentally represent specific navigational sequences before they take them (Corballis,
2013). Nevertheless, even if there is a correlation between mental representations and future
behavior, it need not necessarily follow that rodents (or other animals) pre-emptively embed
these representations within a specific future context (i.e., represent them as future
representations). Among humans, representations of potential future events are often
spontaneous and detached from awareness of the temporal location of these events (e.g.,
during mind-wandering), even though such representations may influence actual future
behavior (Baird, Smallwood, & Schooler, 2011; Stawarczyk, Cassol, & D'Argembeau, 2013).
If similar cognitive processes occur in rodents, then it remains plausible that they experience
navigational representations as an adaptive form of temporally-detached mental imagery,
rather than actively planning future routes as humans can (see Redshaw, 2014). Recent
Running head: FUTURE THINKING IN ANIMALS 7
computational modelling suggests that offline sequential firing in rodent hippocampal place
cells may even be generated randomly by neural network activity (Azizi, Wiskott, & Cheng,
2013).
Regardless of the underlying cognitive processes, neurological studies of rodent route
planning have thus far focused only on navigation through very simple spatial fields.
Ecological studies with great apes, on the other hand, have claimed to provide evidence of
route planning through complex natural environments. Female chimpanzees in the Tai forest,
for example, have been found to prefer sleeping in nests that are closer to breakfast sites
containing ephemeral, high-calorie fruits than breakfast sites containing other fruits (Janmaat,
Polansky, Ban, & Boesch, 2014). They also leave their nests earlier when they breakfast on
ephemeral fruits, especially when these fruits are further away. These findings led the authors
to conclude that the chimpanzees were flexibly planning their sleeping and nest-leaving
behaviors with breakfast in mind (for similar route-planning claims in male orangutans, see
van Schaik, Damerius, & Isler, 2013).
Ecological studies are extremely valuable for documenting the natural future-oriented
behaviors of great apes and other species. The problem with drawing strong conclusions
about future thinking from such research, however, is that we cannot rule out whether the
behaviors observed are the product of innate predispositions, learning processes, or a
combination thereof (Thom & Clayton, 2015a). Future-oriented behavior is pervasive
throughout the animal kingdom and need not necessarily require sophisticated temporal
representations (Suddendorf & Corballis, 2007). It seems plausible, for instance, that natural
selection would favor chimpanzees with an innate preference for sleeping closer to
ephemeral, high-calorie fruits, even if these individuals were not specifically considering the
next day’s breakfast when doing so. Natural selection would also favor chimpanzees with a
predisposition towards leaving earlier in their circadian cycle when travelling to breakfast
Running head: FUTURE THINKING IN ANIMALS 8
sites that were further away (according to their cognitive map). If chimpanzees are truly able
to flexibly plan breakfast, then they should be able to do so in an experimental setting in
which the natural contingency between proximity and ease of access to the next day’s food is
reversed (such that they must choose to sleep further away from a breakfasting area in order
to more easily access it tomorrow).
Intertemporal Choice and Delayed Gratification
Animals often forgo immediate opportunities or incur immediate costs in favor of
longer term benefits (Fawcett, McNamara, & Houston, 2012; Stevens & Stephens, 2008).
When a spider builds a web that may later catch prey, for instance, energy must be expended
to produce the silk and to spin the threads, and other opportunities (e.g., to mate) must be
forfeited. Thus building a web, along with many other activities in the animal kingdom –
from hibernating to caching food to searching for a mate – can be construed as intertemporal
trade-offs between immediate and delayed outcomes (Stevens, 2010). While these behaviors
are typically referred to as ‘choices’, however, at least some of them likely involve no
thinking about the future reward at all (Stevens, 2011). Few would attribute the spider in the
above example with any mental representation of the rewards it stands to receive from its
patience, for instance. On the other hand, larger-brained animals such as birds, rodents and
primates are also faced with intertemporal trade-offs, the underlying cognitive mechanisms of
which are more contentious (Thom & Clayton, 2015b). Foraging is a classical case: an animal
encountering an unripe fruit must decide whether to eat it now or wait for it to ripen in order
to reap the benefits of improved taste and nutrition (Dasgupta & Maskin, 2005).
In standard laboratory intertemporal choice tasks an animal is presented with two
options: one that will trigger an immediate reward, and one that will incur a delay until
reward onset. Although rats and pigeons generally exhibit a global preference for immediate
reinforcement, they will sometimes choose to delay their gratification for a few seconds for a
Running head: FUTURE THINKING IN ANIMALS 9
larger reward than an immediately available one in these tasks (Tobin & Logue, 1994). Both
new and old world monkeys tend to wait less than a minute for the larger reward (Santos &
Rosati, 2015), whereas chimpanzees may wait up to two minutes (Rosati, Stevens, Hare, &
Hauser, 2007). Other paradigms assess the related construct of delay maintenance – or how
well an animal can hold out for a larger later reward in the face of immediate temptation. In
‘accumulation’ tasks a small reward will gradually build up until the animal chooses to
retrieve it, and chimpanzees have been shown to wait for up to three minutes for chocolate
pieces to accumulate before consuming them (Addessi et al., 2013; Beran, 2002). In
‘exchange’ tasks, on the other hand, a small reward must be kept in possession for a period of
time before being traded back to the experimenter for a larger one. Chimpanzees may delay
gratification for up to 8 minutes when the delayed reward is 40 times larger than the one
initially provided (Dufour, Pelé, Sterck, & Thierry, 2007).
Although some authors have suggested that animals’ intertemporal choice behavior
may rely on some form of future thinking (Roberts, 2012; Santos & Rosati, 2015), there are a
number of reasons to be skeptical. Standard dichotomous choice scenarios are usually
presented in highly artificial environments in which many trials are used to teach the time lag
associated with the delayed options (Mazur, 1987). For instance, the two rewards (large and
small) generally start off both being delivered immediately, with a slight delay added to the
larger reward every time it is chosen. Furthermore, because these studies often present both
the delayed and immediate options simultaneously, with the only difference being the
inferred wait that the animal has learned previously, it is possible for the subject to simply
associate each of the options with the outcome it engenders if chosen (including the negative
emotion associated with waiting for the larger reward), without necessitating a mental
representation of the delay itself. In the accumulation task this problem is somewhat abated,
though the animal can still see the rewards building up and is therefore reinforced in their
Running head: FUTURE THINKING IN ANIMALS 10
waiting behavior with every food item that is added. Successful performance on exchange
tasks probably signifies the most convincing evidence of some degree of future reward
representation, though such tasks typically still involve a long period of training to teach the
trade behavior, and it is difficult to rule out the possibility that the subjects simply lose
interest in the small reward and subsequently exchange it when it returns to their attention.
Sometimes it is more adaptive to select an immediate reward instead of a larger but
delayed one, for example when the environment is particularly harsh or uncertain (Fantino,
1995; Fawcett et al., 2012; Frankenhuis, Panchanathan, & Nettle, 2016). A capacity to
flexibly adjust intertemporal preferences as a function of anticipated outcomes might
therefore be a particularly informative avenue for exploring future-oriented thinking in the
context of intertemporal choice (Bulley, Henry, & Suddendorf, 2016; Cheke, Thom, &
Clayton, 2011). Bonobos have been found to adjust the amount of time they are willing to
spend waiting for future rewards when the administering experimenter has proven themselves
unreliable, perhaps because they are ‘expecting’ delayed rewards to be less likely to
materialize (Stevens, Rosati, Heilbronner, & Mühlhoff, 2011). Similarly, squirrel monkeys
have been found to gradually change their choice preferences to a smaller reward when they
learn that this choice will eventually lead to a larger reward amount (McKenzie, Cherman,
Bird, Naqshbandi, & Roberts, 2004). The animals in these studies, however, were taught that
their food amounts would change as a function of their choices over a number of trials, so it
is plausible that they learned to associate the two options with different outcomes. To test
whether an animal could flexibly adjust intertemporal choices as a function of anticipated
(rather than learned) outcomes, an experiment could be devised in which the reward options
varied in perishability. For instance, if a chimpanzee first learned that 1 piece of food from
Tray A would always be given immediately upon selection, whereas 10 pieces of the same
Running head: FUTURE THINKING IN ANIMALS 11
food from Tray B would not be given until after a delay, then would it subsequently be less
likely to select Tray B if the trays contained a quickly perishing food (e.g., flavored ice)?
Avoiding Future Threats
The future holds the potential for abundant opportunities and rewards, but it also
contains myriad potential threats. Whereas manifest threats tend to be responded to with a
complex suite of processes collectively labelled as a ‘fear’ or ‘defensive’ response (LeDoux,
2014), many animals are also capable of responding to threats with a more advanced
preparatory window. Such preparation for threats before they materialize is associated with a
different set of physiological and cognitive reactions that together constitute an ‘anxiety’
response (Bateson, Brilot, & Nettle, 2011; Damasio, 1995). This response entails the
secretion of stress hormones and a change in heart rate, but also hypervigilance and
precautionary behaviors oriented towards sampling more information and discerning the
optimal reaction to the implied danger. In essence, the anxiety response can be thought of as
extending the amount of time an animal has at its disposal to deal with potential threats
before they eventuate. This response can be evoked both by specific cues of a possible threat
such as the smell of a predator, but also via an appraisal of ‘general vulnerability’, for
instance based on interoceptive signals that indicate the current healthiness of the body
(Bateson et al., 2011).
The threat reaction is thereby highly flexible and its expression varies as a function of
a number of variables pertaining to, among others, the state of the organism, its recent
experiences and ecological conditions (Bateson et al., 2011; Nettle & Bateson, 2012). Many
prey animals, for example, exhibit vigilant ‘checking’ behavior in open areas where they are
susceptible to predation, while nocturnal animals show anxiety in bright light (Bednekoff &
Lima, 1998; Burman, Parker, Paul, & Mendl, 2009; Underwood, 1982). Despite being
impressively future-oriented and often flexible, however, such a preparatory anxiety response
Running head: FUTURE THINKING IN ANIMALS 12
does not necessarily demonstrate mental representations of the future. Rather, this response
may be largely dependent upon perceptible cues of specific or general threat in the immediate
environment alongside physiological signals about current vulnerability (Apfelbach,
Blanchard, Blanchard, Hayes, & McGregor, 2005). It is possible that animals may also
employ memory traces of aversive past events associated with such cues in modifying their
responses. However, a capacity to think about and act against specific potential future threats
without relying on external or vulnerability cues has thus far been demonstrated only in
humans (Miloyan, Bulley, & Suddendorf, 2016).
Thus far, nearly all experimental research into animal future thinking capacities has
focused on preparation for future opportunities and rewards, rather than for future threats. In
the previous section, however, we outlined how animals tend to be largely impatient and
prefer immediately available rewards relative to larger, later ones; and therefore it may be
somewhat unsurprising that animals fail certain future thinking tasks where they must pursue
delayed rewards. Still, it remains possible that they could pass structurally similar tasks
requiring them to plan for upcoming dangers. Indeed, threats to fitness are a potent source of
selective pressure and likely played a critical role in the evolution of future-oriented
cognition (Miloyan et al., 2016; Mobbs, Hagan, Dalgleish, Silston, & Prévost, 2015).
Nevertheless, given the ethical concerns with experimental manipulations that have the
potential to induce strong negative emotion, future research in this area may be largely
confined to observational studies.
Acquiring and Constructing Tools to Solve Future Problems
Some of the most commonly cited evidence of animal future thinking comes from
studies of great apes’ capacity to select tools and use them after a delay to solve a problem
and obtain a reward. In the earliest of these studies (Mulcahy & Call, 2006), bonobos and
orangutans were first trained to use a tool to retrieve a food reward, and were then presented
Running head: FUTURE THINKING IN ANIMALS 13
with a free choice of tools (including the trained tool) to transport out of the room while the
reward was unavailable. The apes transported the appropriate tool more often than
inappropriate tools, and a few of them were more likely to bring the appropriate tool back to
the room and use it when the reward became available again (one or 14 hours later). A second
study replicated these findings with chimpanzees and orangutans in a forced choice paradigm
(where they could only choose one tool), while also showing that the subjects sometimes
preferred the appropriate tool over an immediate small food reward (Osvath & Osvath, 2008).
Impressively, the final experiment in this follow-up study found that the apes were more
likely to choose novel tools that could solve the future problem than novel tools that could
not.
Concerns exist over whether the apes’ success in these paradigms could be explained
by associative learning, given that the appropriate tools (or similar ones) had been previously
reinforced during the training phases (Suddendorf, 2006; Suddendorf, Corballis, & Collier-
Baker, 2009). Even setting aside this particular low-level explanation, however, such
experiments can only go so far in demonstrating apes’ future thinking. It seems plausible, for
instance, that seeing an appropriate tool would trigger an immediate representation of the
reward it can retrieve (such representations are easily cued in humans; Tulving & Thomson,
1973); and so the apes could make their choice based on this immediate representation rather
than any expectation of a specific future event in which the reward becomes available again.
And then when the reward does become available they simply retrieve the tool to which they
have convenient access. In this manner their initial representations would indeed be ‘future-
oriented’, but only from an objective perspective rather than from the apes’ own perspective
(Redshaw, 2014). Such explanations could potentially be ruled out by visibly destroying the
reward apparatus (and then removing it from view) before testing whether the apes continued
to choose the now useless tool. If they did not, it might suggest they made their initial choices
Running head: FUTURE THINKING IN ANIMALS 14
based on flexible representations of the future, rather than rigid representations triggered by
seeing the tool.
One recent study gave great apes the opportunity to construct tools that could be used
to solve a future problem and obtain a reward (Bräuer & Call, 2015). Chimpanzees, bonobos
and orangutans were introduced to an apparatus that required them to bite off and insert
pieces of wood into tubes in order to retrieve grapes. Once a piece of wood had been inserted
into a tube it could no longer be retrieved, such that the apes had to bite off multiple pieces of
wood in order to retrieve grapes from multiple tubes. After learning how to do this, the apes’
access to the apparatus was temporarily blocked by a transparent flexiglass panel, and either
0, 1, or 8 of the tubes were baited with grapes. While waiting for the apparatus to become
accessible again, the apes were more likely to prepare useful pieces of wood when grapes
would be available in the future (for a limited time) than when they would not. They also
prepared significantly more tools in the 8 grapes condition than the 1 grape condition, but not
excessively so (on average they produced less than two tools in the 8 grapes condition).
These results do indeed show that great apes can prepare tools that will enable them to
obtain a currently-unavailable reward in the near future, but they also point to important
limitations. Firstly, it remains to be seen whether apes could succeed at the task if visual
access to the apparatus was blocked, and the future availability of grapes (or lack thereof) had
to be represented in working memory. Moreover, the pattern of responses suggests that the
apes were not particularly sensitive to the specific contingencies of the problem. They
showed no evidence of producing even close to the optimal number of tools in the 8 grapes
condition, which suggests they may have been producing them based on a rough rule (e.g.,
‘more visible grapes = make more tools’) rather than the precise requirements of the task (i.e.,
‘make one tool per visible grape’). The apes’ difficulty with the 8 grapes condition and the
Running head: FUTURE THINKING IN ANIMALS 15
more general capacity to produce multiple tools to solve multiple future problems may be
related to limitations in number representation (Matsuzawa, 2009).
Acquiring, Saving, and Exchanging Tokens for Future Rewards
Money is a powerful reinforcer for humans primarily because we recognize that it can
be exchanged for desirable items and experiences in the future. Researchers have investigated
whether non-human primates, too, can acquire, save and eventually exchange tokens for
future rewards. In one of the earliest of these studies (Dufour & Sterck, 2008), chimpanzees
were first trained to return a colorful straw to an experimenter in order to receive peanuts. In
the subsequent test phase, they were given the opportunity to collect straws and two types of
distractor objects, transport them to another room when ushered away, and then come back to
the first room an hour later and exchange the straws for peanuts. The distractor objects were
also associated with rewards (a branch that could be used to retrieve honey and a stick that
could be used to retrieve fruit pieces), but not in an exchange context, in order to rule out the
possibility that the subjects simply preferred the straws because of their previous positive
reinforcement. The results showed that the chimpanzees often transported the straws and
distractor objects out of the room when ushered away, but they rarely returned and exchanged
the straws for peanuts (the best performer exchanged straws on 2/10 trials). Critically, the
subjects showed no significant preference for returning to the testing room with straws
compared to the distractor objects, suggesting that they were not specifically considering the
future exchange task when returning to the room.
A similar study produced contrasting results, although there was one important
methodological difference. Osvath and Persson (2013) showed that chimpanzees and
orangutans preferred to transport, return with, and exchange the previously reinforced token
instead of distractor objects, and they also preferred to the select the token over distractors in
a forced-choice paradigm. Unlike in the earlier study, however, the distractor items were
Running head: FUTURE THINKING IN ANIMALS 16
novel and not positively associated with rewards in any context. Prior to training, the subjects
showed no inherent preference for selecting the correct token instead of the distractors, but it
seems likely that the apes would have quickly acquired a preference for the token after they
had been taught to return it for food. It therefore cannot be ruled out that the subjects
preferred to select and transport the correct token instead of the distractors simply because of
the token’s unique association with rewards. A final study showed that bonobos and
orangutans also acquired, transported, and later exchanged items for rewards (Bourjade, Call,
Pelé, Maumy, & Dufour, 2014), but these results are also equivocal as there were no
distractor objects for the apes to select.
The differential pattern of responding across these studies elegantly illuminates where
apes’ limitations in exchange tasks may lie. Specifically, it appears they may select and
transport tokens based on their past utility, rather than representing and reasoning about the
specific future exchange context in which they will become useful. In Dufour and Sterck’s
(2008) study, the distractor items also had past utility (albeit in a non-exchange context), and
so they were preferred an equal amount to the tokens. In the later studies, however, the tokens
were preferred based on their unique past utility, regardless of the fact they would become
useful in the future. The preference for past utility could be based on simple associative
valence (Suddendorf, 2006; Suddendorf et al., 2009) or it could be based on cued mental
representations (i.e., episodic memory traces) of previous occasions when the token was
useful (Cheng et al., 2016; Redshaw, 2014).
Acting with Future Desires in Mind
For nearly two decades, animal future thinking researchers have been trying to falsify
the Bischof-Köhler hypothesis (Suddendorf & Corballis, 1997), which proposes that animals
cannot imagine and prepare for a future motivational state that conflicts with their current
motivational state (e.g., they cannot imagine and prepare for future hunger when sated). As
Running head: FUTURE THINKING IN ANIMALS 17
Suddendorf and Corballis (2007) point out, animals incapable of anticipating future drive or
need states would “have little reason to concern themselves with a remote future” (p. 306), on
account of the fact that only present needs would matter to such animals. Early observations
suggested that animals had great difficulty imagining future desires (e.g., Roberts, 2002), but
more recent studies have produced some provocative findings.
In the earliest study that claimed to falsify the Bischof-Köhler hypothesis, Naqshbandi
and Roberts (2006) gave two squirrel monkeys a choice between selecting one piece of date
with water available after 30 minutes, or four pieces of date with water available after 180
minutes. The monkeys eventually began to prefer the former option, with the authors arguing
that they made their selection in order to reduce future thirst levels (as dates induce thirst).
Nevertheless, the fact that the monkeys gradually began to prefer the one date over many
trials suggests the involvement of associative learning; and moreover, if they were truly
acting for future desires then they should have selected the four pieces of date and simply
waited until water became available before eating them (Suddendorf & Corballis, 2010). The
result could not be replicated in a sample of six rhesus monkeys (Paxton & Hampton, 2009).
One of the most interesting lines of evidence in this area comes from a pair of
observational studies with a male chimpanzee, Santino. Zookeepers and researchers
witnessed him storing piles of stones on some mornings before later hurling them at zoo
visitors (Osvath, 2009; Osvath & Karvonen, 2012). These observations were met with claims
that Santino may have been preparing for future occasions when he would desire to display
his dominance towards the zoo visitors (the stone collecting behavior appeared to occur in a
calm state, whereas the hurling behavior typically occurred in an aroused state). Nevertheless,
it remains unclear just how oriented towards specific future events his stone storing activities
were, rather than being driven by more general mental representations (i.e., episodic memory
traces) of zoo visitors appearing (Redshaw, 2014). These observational findings must be
Running head: FUTURE THINKING IN ANIMALS 18
replicated in an experimental setting before they can begin to seriously question the Bischof-
Köhler hypothesis.
Perhaps the strongest challenge to the Bischof-Köhler hypothesis comes from a clever
line of research with birds from the Corvidae family, which have a natural proclivity for
caching and retrieving food (e.g., Correia, Dickinson, & Clayton, 2007; Raby, Alexis,
Dickinson, & Clayton, 2007). The most convincing of these studies (Shettleworth, 2012)
exploited the fact that corvids and other animals prefer not to eat a specific food (in
comparison to other foods) once they have become sated on that food. Eurasian jays were
first fed a particular food (e.g., peanuts) to the point of satiation, and subsequently preferred
to store that food in a specific cache that would only be available to retrieve from when they
would prefer the food again in the future (Cheke & Clayton, 2012). Thus it appeared the birds
were ignoring their current distaste for the food in order to act for their future preference.
Nevertheless, the authors conceded that the jays could have simply learned to associate an
emotional preference for the food with the appropriate storage location during the training
phase, with this preference becoming reactivated when the birds were given the opportunity
to cache. In other words, the birds might have not been acting based on a ‘future’ desire state,
but rather a cued current desire state that just happened to match the future desire (Redshaw,
2014).
Emotional states seem particularly susceptible to such reactivation, in that they can be
cued by environmental factors and experienced in the present to motivate behaviors with
incidental future benefits (see Boyer, 2008; Damasio, 1989; Osvath & Martin-Ordas, 2014).
So-called ‘interoceptive states’ (e.g., general hunger, thirst, temperature sensitivity), on the
other hand, arise more directly from the peripheral nervous system (Craig, 2002) and may be
less susceptible to reactivation. Tests of the Bischof-Köhler hypothesis should perhaps
therefore focus on whether animals can act for future interoceptive states if they wish to rule
Running head: FUTURE THINKING IN ANIMALS 19
out associative reactivation as an explanation. Nonetheless, acting for such states may be
genuinely beyond the capacity of animals. Among humans, children struggle to act for future
thirst levels until at least age seven and possibly beyond (Atance & Meltzoff, 2006; Mahy,
Grass, Wagner, & Kliegel, 2014). Indeed, even adults struggle to pre-experience future
interoceptive states (try to ‘experience’ hunger the next time you finish a very large meal, for
example), and so our capacity to act for such states may be largely based on an abstract
understanding of temporal shifts in motivation rather than any analogue representation of the
states themselves. If there is truth to the Bischof-Köhler hypothesis, then, it may be that
animals cannot represent desire states in a propositional fashion in the way that humans can.
Synthesis
The previous sections have described evidence for non-human animals’ future-
oriented behavior in a number of domains (see Table 1 for summary). In each section we
have encountered examples of animals acting in ways that make future events more
pleasurable and/or less painful. It is not surprising that such behaviors would be apparent in
the animal kingdom, given that natural selection can clearly act on how a behavior affects an
animal’s future survival or reproductive chances (Klein, 2013; Schacter & Addis, 2007;
Suddendorf & Corballis, 2007). It is also not surprising that some of these behaviors would
be underpinned by cognitive processes, in that certain animals can represent states of reality
that correlate with actual future events and subsequently behave in a manner that provides
tangible fitness benefits. Indeed, some of the most influential unified theories of neuroscience
propose that brains are essentially ‘prediction machines’, that through a continuous,
potentially Bayesian-like process of comparing expected and actual outcomes, become ever
more optimal at anticipating events in the immediate environment (Bar, 2007; Clark, 2013;
Friston, 2010). And at least some of the predictions generated by the brain may be based on
episodic memory traces triggered by the presence of relevant external cues (Cheng et al.,
Running head: FUTURE THINKING IN ANIMALS 20
2016; Redshaw, 2014). In this particular sense, animal future thinking may be basically
continuous with the human capacity.
In each domain, however, we have also encountered important potential limitations.
Some of these potential limitations may eventually require reconsideration; future research
may well demonstrate that animals are capable of more complex future thinking and behavior
than is currently known. On the other hand, in comparison to human future thinking at least,
it seems almost certain that some genuine limits exist. Moreover, some of these limits may be
overarching, in that they restrict future-oriented behavior across several domains. A recurring
theme throughout our analysis, for example, has been the lack of any evidence that animals
represent future representations as future representations – a form of ‘metarepresentation’
that may be critically important in various flexible human future-oriented behaviors
(Redshaw, 2014; Suddendorf, 1999). In fact, Schopenhauer (1818/1909) first proposed this
fundamental discontinuity between humans and animals nearly 200 years ago, when he
claimed that the principal component missing from animal minds was “distinct consciousness
of the past and of the eventual future, as such, and in connection with the present” (p. 229,
emphasis original).
Metarepresentation is important for future thinking not necessarily in that it enables
more vivid future imagery, but rather because it allows agents to represent the properties of
future imagery, such that potential future events can be explicitly contrasted with both current
reality (Kappes & Oettingen, 2014; Oettingen, 2012; Redshaw, 2014) and with other
potential future events (Gollwitzer, 2014). A predictive brain may indeed be ideally suited to
representing likely outcomes of an event, but some future events cannot be anticipated with
any certainty by even an optimal predictive brain (consider, for example, the often erratic
behavior of predators and prey). An agent with an additional capacity for forming
metarepresentations, on the other hand, can reflect on the natural representational limits of
Running head: FUTURE THINKING IN ANIMALS 21
their own mind and flexibly compensate for these limits. The human ability to develop and
enact contingency plans, for instance, relies on an understanding that future events do not
always unfold as expected or desired, and so it pays to also prepare for mutually exclusive
alternatives. A traveler may imagine and prepare for a dream overseas holiday, but they may
also purchase insurance in case something goes wrong and their original plan must be
abandoned. On a broader scale, governments and other institutions are tasked with guiding
human societies towards prosperous versions of the future, but they must also plan for
potential large scale emergencies and disasters.
One recent study examined the capacity to simultaneously prepare for two mutually
exclusive outcomes of a very basic, immediate future event in 2- to 4-year-old children and a
sample of 8 great apes (Redshaw & Suddendorf, 2016). Subjects were given the opportunity
to catch a desirable item that was dropped into a forked tube with one opening at the top and
two possible exits at the bottom. The apes (like 2-year-olds) typically covered only one exit
when preparing to catch the item, whereas most of the 4-year-olds consistently covered both
exits from the first trial onwards. The apes thus failed to provide evidence for an insightful
capacity to consider and prepare for multiple, mutually exclusive future event outcomes.
Nevertheless, it remains possible that future studies with other subjects, species, and/or
paradigms will discover some competence.
Another domain in which humans often reflect on and compensate for their future
thinking limitations is prospective memory, which involves remembering to perform an
action at some particular future occasion. Because we recognize the chance that we will
forget to perform the action, many of us use calendars, alarms, lists, and other external
reminders as aids (Gilbert, 2015; Risko & Gilbert, 2016). Indeed, many human institutions
would collapse entirely if it were not for future-oriented record-keeping procedures that
preclude the need for perfect memories (e.g., consider legal and financial systems). There
Running head: FUTURE THINKING IN ANIMALS 22
have been some claims for prospective memory in great apes (Beran, Perdue, Bramlett,
Menzel, & Evans, 2012; Perdue, Evans, Williamson, Gonsiorowski, & Beran, 2014), with
experiments showing that they remember to request or exchange a token for food after
completing another irrelevant task (for similar claims in rats, see Crystal, 2013).
Nevertheless, it remains possible that no future thinking was involved in these studies, and
instead the apes were simply cued into action after completing the irrelevant task. There is
nothing to indicate that great apes or other animals spontaneously set their own reminders in
order to improve their likelihood of remembering to perform future actions.
Certain species naturally act on their environments to store information that will be
useful in the future. Consider, for example, ants that leave a pheromone trail between their
nest and a food source (Sterelny, 2003). The question here, however, is whether any animals
can do so in various novel contexts as humans can. This would indicate a domain-general,
flexible capacity for strategic reminder setting, rather than an instinctual fixed action pattern
confined to a narrow domain (for more general arguments along these lines, see Premack,
2007; Suddendorf & Corballis, 2010). One could examine this ability, for instance, in a
delayed object permanence paradigm, where an animal has to wait a specified period of time
before they can select (from some options) the location where an experimenter has hidden
food. Would the animal spontaneously and consistently mark the correct location with a body
part (or scent) or other object during the waiting period in order to increase their chances of
remembering it?
To summarize, there remains no evidence that animals metarepresent future
representations as future representations; as mere possibilities that could be otherwise
because of the mind’s inherent inability to predict some aspects of future events with
certainty. Humans, on the other hand, reflect on and flexibly compensate for their future
thinking limitations to acquire enormous benefits. Nevertheless, it is important to remember
Running head: FUTURE THINKING IN ANIMALS 23
that an absence of evidence is not the same as evidence of absence, and thus future studies
should give animals more opportunities to demonstrate such a capacity. Here we have given
two possible lines of evidence to pursue: (1) the ability to spontaneously and simultaneously
prepare for multiple, mutually exclusive versions of the future, and (2) the ability to
spontaneously set reminder cues in prospective memory tasks. Any results suggesting that
animals did or did not possess these abilities would likely inspire debate and alternative
interpretations, but with increasing refinement of experimental manipulations it is certainly
possible to make progress on such important questions.
The Phylogeny of Future Thinking
Absence of evidence is not only a specific problem for certain domains of animal
future thinking, but also more a general problem when considering the relatively miniscule
number of species that have been tested in controlled settings. The performance of great apes
and other primates is of particular interest, of course, given the potential for shedding light on
the evolution of human-like future-oriented mechanisms by studying closely related species.
Nevertheless, by examining patterns of capacities and limits across vastly different taxa, one
could potentially reason about the biological and environmental factors responsible for the
emergence of future thinking in general (whether that be ‘mere’ predictive cognition or
higher-order capacities). For example, does future thinking tend to arise as a by-product of
domain-general cognitive specialization? Or does it tend to emerge in response to critical
environmental pressures such as highly uncertain future rewards or threats that precipitate a
need for advanced preparation? And what role do overall brain size, neocortex ratio, or other
neurological factors play? These questions will remain moot, however, until more studies are
carried out with non-primate taxa other than corvids and rodents. Prime research candidates
include taxa that have demonstrated impressive cognitive skills in other domains, such as
elephants (e.g., Foerder et al., 2011), cetaceans (e.g., Marino et al., 2007), domestic dogs
Running head: FUTURE THINKING IN ANIMALS 24
(e.g., Range, Viranyi, & Huber, 2007), and parrots (e.g., Pepperberg, Willner, & Gravitz,
1997). Even certain invertebrates, such as coleoid cephalopods (i.e., octopuses, squid and
cuttlefish), are worthy of investigation, given their notable problem-solving and tool use
capacities (Vitti, 2013).
Importantly, although discussions of ‘animal’ future thinking are traditionally
confined to extant species other than modern humans, we must also consider that Homo
sapiens are only the last survivors of a rich hominin lineage. Indeed, archaeological evidence
suggests that hominin future thinking has undergone radical changes in the last few million
years. Over one million years ago in east Africa, for example, our Homo erectus predecessors
were making many more Acheulean tools than were necessary for everyday use (Kohn &
Mithen, 1999). Given that such tools are notoriously difficult to craft, it is possible these early
humans were deliberately practicing tool manufacture with future expertise in mind
(Rossano, 2003) – a behavior that may be out of reach for extant animals (Suddendorf,
Brinums, & Imuta, in press). Other novel future thinking capacities are likely to have
emerged in our more recent ancestors, such as Homo heidelbergensis, as the ability to harness
the future continued to be a prime mover in human evolution (Suddendorf & Corballis,
1997). If any of our recently extinct cousins were still walking the earth – such as Homo
neanderthalensis or the Denisova hominin – then the potential limits column in Table 1
would likely be considerably bare (see Suddendorf, 2013b).
Conclusion
Contemporary comparative psychologists have shown animals to be capable of far
more complex future-oriented behaviors than was once thought possible. Here we have
reviewed the available evidence and suggested that at least some of these behaviors are based
on mental representations that go beyond the here-and-now. Such representations probably
function to motivate present action that provides tangible future benefits across various
Running head: FUTURE THINKING IN ANIMALS 25
domains. Nevertheless, there remain important questions regarding just how much insight
animals have into their own future thinking processes. There is no current evidence to suggest
that animals metarepresent and behaviorally compensate for their natural future thinking
limits – an overarching capacity that enables humans to acquire additional and substantial
benefits. Much further research is needed to shed light on the continuities and potential
discontinuities between human and animal future thinking capacities, and on the evolutionary
circumstances that give rise to these capacities.
Running head: FUTURE THINKING IN ANIMALS 26
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Running head: FUTURE THINKING IN ANIMALS 38
Table 1.
Animal Future Thinking Capacities and Potential Limits across Domains
Future thinking domain Capacities Potential limits
Navigation and route
planning
Neural simulation of familiar and
novel routes through known
environments, and subsequent
pursuit of the same routesr
Strategic nesting and calling
behaviors that increase future
foraging and reproductive success
in distant locationsp
May involve temporally-detached
mental imagery, rather than active
planning
Ecological evidence only; behavior
may be based on innate
predispositions and/or associative
learning
Delayed gratification and
temporal discounting
Selecting a larger, delayed reward
over a smaller but immediate oneg;
waiting for food to accumulate
before eatingp; retaining a small food
reward without eating before
exchanging it for a larger rewardp
May be limited to very short periods
of time; and may be based on learned
associations between options and
outcomes
Preparing for future
threats
Anxious affect produces
hypervigilance and other
physiological responses to prepare
for potential threatsg
May be limited to instances in which
immediately perceptible cues of
threat are available; and may require
learned associations between the cue
and negative outcomes (and/or innate
predispositions to fear the cue)
Selecting and
constructing tools to
solve future problems
Selecting an appropriate tool that
can solve a non-visible future
problem and using it when the
opportunity arisesp
Making an appropriate tool to solve
a future problem and using it when
the opportunity arisesp
May require past experience using an
identical or similar tool successfully
on the same problem, and thus tool
selection may be based on rigid
memory traces of past tool use rather
than flexible future representations
May require the future problem to be
visible; and may struggle to make
multiple tools when multiple future
problems can be solved
Collecting tokens and
exchanging them for
future rewards
Selecting a token and returning it
for a reward after a delayp
May be based on the past utility of
the token rather than its ability to be
used in a specific future exchange
context, given that no preference is
observed when distractor items also
have past utility
Acting for future desire
states (Bischof-Köhler
hypothesis)
Acting in a manner consistent with
a future desire statec, p
May require the future desire state to
be triggered (i.e., experienced in the
present) by pre-learned associations
with the behavioral context; and may
not apply to interoceptive desire
states that arise more directly from
the peripheral nervous system
Note. Each point in the capacities column corresponds to one point in the potential limits column. Superscripts
indicate the taxa that the evidence applies to: p = primates, r = rodents, c = corvids, g = animals in general.

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