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Anim Cogn (2005) 00
DOI 10.1007/s10071-005-0008-1
REVIEW
´
Adam Mikl
´
osi · Krisztina Soproni
A comparative analysis of animals’ understanding of the human
pointing gesture
Received: 27 February 2004 / Revised: 28 February 2005 / Accepted: 7 July 2005
C
Springer-Verlag 2005
Abstract We review studies demonstrating the ability of
some animals to understand the human pointing gesture.
We present a 3-step analysis of the topic. (1) We compare
and evaluate current experimental methods (2) We compare
available experimental results on performance of different
species and investigate the interaction of species differ-
ences and other independent variables (3) We evaluate how
our present understanding of pointing comprehension an-
swers questions about function, evolution and mechanisms.
Recently, a number of different hypotheses have been put
forward to account for the presence of this ability in some
species and for the lack of such comprehension in others. In
our view, there is no convincing evidence for the assump-
tion that the competitive lifestyles of apes would inhibit the
utilization of this human gesture. Similarly, domestication
as a special evolutionary factor in the case of some species
falls short in explaining high levels of pointing compre-
hension in some non-domestic species. We also disagree
with the simplistic view of describing the phenomenon as
a simple form of conditioning. We suggest that a more sys-
tematic comparative research is needed to understand the
emerging communicative representational abilities in ani-
mals that provide the background for comprehending the
human pointing gesture.
Keywords Communication
.
Pointing
.
Comparative
social cognition
.
Apes
.
Dogs
.
Seals
.
Dolphins
Introduction
Historical background
Although researchers interacting with their animal subjects
often use communicative signals both in the laboratory and
´
A. Mikl
´
osi (
) · K. Soproni
Department of Ethology, E
¨
otv
¨
os Lor
´
and University, Budapest,
P
´
azmany P 1/c,
H-1117 Budapest, Hungary
e-mail: miklosa@ludens.elte.hu
in the field, until recently there was no systematic study
aimed at investigating to what extent animals comprehend
human gestural signals and whether such communication
affects the behaviour of animals. There have been, however,
many anecdotal accounts, some followed up with experi-
ments, which have suggested that some individuals could
indeed react differentially to human given cues (for some
examples see Candland 1993). Animals with a longer do-
mestication history might have some advantage and also
individuals that were raised by humans from a very young
age. Perhaps the most well-known case was about a horse
(“Clever [Kluger] Hans”), which reportedly was able to
“count and read” (Candland 1993; Rosenthal 1965). Oskar
Pfungst (1911) was among the first to show that the horse’s
“extraordinary abilities” were based on its sensibility to
observe and react to minute changes in body tension of the
human experimenter.
The case of Clever Hans made researchers more cau-
tious and as a consequence, textbooks in both experimen-
tal psychology and ethology have argued that researchers
should avoid getting in communicative interactions with
their subjects because inadvertent cueing during training
or testing could influence the behaviour and therefore the
performance of experimental subjects. This warning has
been taken seriously and since then special precautionary
measures are taken to prevent direct contact with the ani-
mals. For example, experimenters separate themselves by a
screen while their subjects make a choice in the Wisconsin
test apparatus, and computers control operant condition-
ing apparatuses while researchers observe their subjects
through one-way mirrors or by the means of closed circuit
video camera systems.
In recent years there has been a renewed interest in inves-
tigating the ability of various animal species to understand
human gestures. The interest in this subject was at least
partially initiated study by Anderson et al.’s (1995), which
used a very simple experimental method to look system-
atically for the effect of experimenter given cues on the
behaviour of the subject. Several studies with various ani-
mals using the same paradigm have followed up this work,
and as of today, more than 20 papers have been published.
Unfortunately, these studies suffer from many conceptual
and methodological problems. The goal of this review is to
facilitate future comparative work by pinpointing some of
the main issues.
The ethological approach: What can we learn
from studying comprehension of human pointing
in animals?
Although it might be of some interest to study how our
gestural communicative system is able to influence the be-
haviour of various species of animals, we would argue that
the controlled investigation of the animals’ ability to under-
stand human communicative signals offers a possibility to
study the cognitive abilities underlying their communica-
tive interactions.
Because most studies preferentially used the pointing
gesture as the main communicative signal, this will be the
focus of the present review. The advantage of using this ges-
ture, pointing with an extended index finger, is that repre-
sents a species specific, human communicative gesture that
is not used on any regular basis by other free living primates
(seeVeaandSabater-Pi1998;forarecentreviewofpoint-
ing in apes see Leavens and Hopkins 1999). In humans,
pointing behaviour emerges toward the end of the first year
but continues to develop until the age of two years when
infants use pointing to direct the attention of the mother
to objects in space (Bates et al. 1977). Comprehension
precedes production, and already 9-month-old infants can
follow with their gaze simple forms of pointing. Research
reveals a gradual development in pointing comprehension
that very likely is the result of an interaction between cog-
nitive development and learning, social experience, social
interaction and communication. This development is fur-
ther facilitated by the own pointing behaviour. We believe
that the comparative research of pointing comprehension
can in principle extend our knowledge in two directions:
First, we can learn about possible evolutionary scenarios
that allowed the emergence of pointing behaviour in our
species, and by it, understand the ultimate and proximate
causes of both its comprehension and production. Second,
the species studied can open a window on their commu-
nicative system. Learning about a communicative signal of
another species can reveal the flexibility of the system as
well as the contribution (or impediment) of species-specific
features to get engaged in inter-specific communication.
Following the footsteps of Tinbergen (1963), we investi-
gate pointing comprehension from three different perspec-
tives:
1. The evolutionary perspective is based on the obser-
vation that the pointing gesture is a specific human
behaviour. Collecting experimental evidence for such
human distinctiveness requires comparative data on
humans and related primate species. Differences and
similarities could show whether abilities associated
with pointing comprehension are restricted to humans
or have some evolutionary antecedents (Povinelli
and Giambrone 1999). A somewhat different line of
argumentation suggests that convergent evolutionary
processes could also lead to the emergence of such
abilities. More specifically, it has been argued that
dogs (and perhaps other domesticated species) are at
advantage in comprehending human communicative
signals (including pointing), because the process of do-
mestication might have selected for such abilities (Hare
et al. 2002; Kaminski et al. 2005; Mikl
´
osi et al. 1998).
2. The functional perspective of pointing comprehension
was emphasized by Hare (2001) when he attempted to
account for some differences in pointing comprehen-
sion between apes and humans. He argued that pointing
is an inherently cooperative type of signal, that is, the
signaller directs the attention of the receiver to an object
or location. It has been hypothesized that pointing com-
prehension should be found in species with a stronger
tendency to cooperate. Based on this, negative results
have been explained by the mainly competitive relation-
ship present in most species of apes and monkeys.
3. The mechanistic perspective is concerned with explain-
ing the cognitive abilities underlying pointing compre-
hension. Earlier it had been thought that pointing com-
prehension could reveal something about the animals’
ability of understanding mental states (Anderson et al.
1995, 1996). It was suggested that the perceiver of a
pointing gesture might attend to the mental state of the
pointer by recognizing its attentive state. Later this hy-
pothesis was referred to as the ‘high-level’ model of
pointing comprehension (Povinelli et al. 1999), and it
was contrasted with the ‘low-level’ interpretation, which
assumed that subjects either use some observable vi-
sual cues to discriminate between situations (associa-
tive discrimination learning), or they use some simple
behavioural automatisms that enables them to track the
goalobjectofthesignalinspace.BasedonCall’s(2001)
recent proposition, a third alternative mechanism can be
suggested. Animals that are able to recognize a situation
as communicative could also be able to deduce after
some experience, a secondary variable (“knowledge” in
Call’s terms), a “rule” that they apply in a novel situation
or context. This explanation assumes a more complex
mental representation of the communicative interaction
(at least the ability to recognize the communicative na-
ture of the cue emitted by the signaller), in contrast
to the simple discrimination learning explanation, but
does not depend on abilities to represent mental states of
others.
A further interesting question is whether animals are able to
comprehend the referential aspect of pointing. In humans
the referential aspect of pointing follows directly from
its imperative and/or declarative nature (Tomasello and
Camaioni 1997), however this does not mean that also an-
imals are necessarily decoding the referential components
of pointing. Although the issue of referentiality remains
controversial in animal communication (see e.g. Owren and
Rendall 1997), here we refer to it as an ability to compre-
hend communicative signals that refer to external events or
objects and their effect seems to be relatively independent
of the context (Allen and Saidel 1998; Evans 1997).
The structure of this review
In the following we will present a 3-step analysis of the
topic. (1) We compare and evaluate current experimental
methods used. (2) We compare available experimental re-
sults on performance of different species and we investigate
the interaction of species differences and other independent
variables. In this section we look for answers on how mod-
ifications of the procedure affect performance (see Table 1)
and whether previous (social) experience influences perfor-
mance, including the effect of development. (3) We try to
evaluate how our present understanding of pointing com-
prehension answers questions about function, evolution and
mechanisms.
It should be noted that because of the divergence of the-
oretical and experimental paradigms, our comparisons will
often be only tentative. Nevertheless, we believe that this
review will provide a starting point for developing more
precise hypotheses and better designed experiments.
Methods
Subjects
Probably because researchers had different theoretical
questions in mind, a wide array of animals have been
tested for pointing comprehension (monkeys: Rhesus
monkey (Macaca mulatta), capuchin monkeys (Cebus
apella); apes: chimpanzees (Pan troglodytes), gorillas
(Gorilla gorilla), orangutans (Pongo pygmaeus); dogs
(Canis familiaris); wolves (Canis lupus); cats (Felis catus);
dolphins (Tursiops truncatus); horses (Equus caballus),
seals (Arctocephalus pusillus), goats (Capra hircus)).
There are however, at least three potential problems when
relying on the comparative argument based on the animals
tested up to now with this paradigm. (1) It should be noted
that given the nature of these tasks in the case of some
species, the number of subjects is very low which could
violate the external validity of the results and eventually
could bias the comparisons. (2) Given the social nature of
the situation, previous individual social experience could
have major influence on the outcome. In many cases we
know little about the age, the individual history of the
subjects and their previous experience with humans that
remains difficult to assess. For example, dogs living in a
family (and sometimes also being trained) are exposed to
a great extent to pointing gestures (personal observation).
The effect of human social experience is problematic in the
case of apes because there is a considerable variation from
using captive apes (with minimal human contact) to home
raised individuals (for categorization on human experience
in apes, see Call and Tomasello 1996), and in addition,
the amount of early socialisation, which can have a strong
effect on social skills in general, is often also not known.
Further, pointing is such a natural behaviour in humans
that it is difficult to assess the amount of previous exposure
to such experience with humans in animals like dolphins or
seals, even if admittedly this gesture was not used during
training (Herman et al. 1999; Tschudin et al. 2001). (3) The
experimental procedures used differ also among the tested
species. This means that comparisons can be done only with
some reservations and negative or contradictory results
can be attributed sometimes to procedural differences.
Procedure(s)
The studies reviewed here are based on the following ex-
perimental procedure: The subject’s out of view food is
hidden in one of two (or sometimes three) bowls that are
placed either on the floor or at particular height. The human
informant stands (or kneels) between them, points to one of
the bowls, and then the subject is allowed to make a choice.
Pre-training often involves familiarization with the bowls
since some subjects have to learn that those might contain
food. The reward is usually presented in semi-random order
(No more than two rewards are hidden on the same side in
subsequent trials to avoid the development of a side bias.).
In some cases subjects (e.g. chimpanzees) are separated
from the human informant by partitions (or “by water” in
dolphins, see Herman et al. 1999; Tschudin et al. 2001),
and in these cases subjects are usually nearer to the bowls
(or goal objects in case of dolphins) than the pointer, or
both participants are at equal distance. In other experiments
both the informant and the recipient are in the same physical
space, and can interact freely (e.g. dogs, goats), and subjects
usually stand further from the bowls.
A further difference concerns the degree of familiarity
with the testing environment and the experimenter. Ani-
mals are sometimes tested in their home environment or in
a familiar environment that is used for testing. The experi-
menter is usually familiar in the case of apes and dolphins,
while often unfamiliar persons test dogs.
Two distinct experimental procedures can be distin-
guished: In the ‘training procedure’, novel gestures are
introduced only one by one, usually only after the ani-
mal had reached significant performance levels with the
previous “simpler” gesture. In this arrangement one can
test for learning ability by measuring differences in learn-
ing rate for different gestures. However, inference from
earlier learning makes interpretation difficult (Anderson
et al. 1995; Mikl
´
osi et al. 1998). In the so-called ‘probe tri-
als procedure’ different and often “unfamiliar” variations
of the pointing gesture are intermixed with simple “base-
line” pointing (for example see Povinelli et al. 1997, 1999;
Soproni et al. 2001, 2002). This method has the advantage
that it usually involves a small number of trials to test the
actual comprehension abilities of the subject, and on the
practical side, the baseline trials also help to maintain the
attention of the subjects, and are indicative of the general
level of responsiveness during the experimental sessions.
Additionally, the response to the first presentation of a novel
gesture can be used to assess the ability for generalization.
Table 1 Summary table for experimental studies of pointing com-
prehension, grouped on the basis of three aspects of the gesture.
The temporal aspect refers to the duration and the dynamics of the
gesture used. The spatial aspects refers to the physical proximity
of the experimenter and the pointing hand to the target object (at
target = the experimenter is standing at the target and is pointing at
the target; proximal =the experimenter is standing at equal distance
from both targets but the tip of pointing finger is within 10 cm of
the target; distal = the experimenter is standing at equal distance
from both targets but the tip of pointing finger is at least 50 cm
from the target; asymmetric = the experimenter is standing at the
non-target, and pointing to the target. Pointing gestures are often not
accompanied by any gazing cues (no gazing = looking at the floor
or wearing non-transparent glasses), experimenters gaze at their sub-
jects during pointing (gazing) or make gaze alterations (gazing at the
subject is followed gazing at the target and vice versa). ± signs in-
dicate significant/non-significant preference for the object indicated
by pointing
Temporal aspect Spatial
aspect
Accompanying attentional cue ((Ref) species (n), result)
No gazing Gazing at target Gazing at subject Gaze alternation
Static At target
Proximal
Distal (8) chimpanzee (7) − (8) chimpanzee (7)
+
(8) chimpanzee (7) −
(23) dolphin (2) +
Cross body (23) dolphin (2) +
Asymmetric
Dynamic At target (19) wolf (4) + (5) chimpanzee (4) +
(14) dog (10) +
Proximal (1) capuchin monkey (3) − (7) gorilla (4) + (9) chimpanzee (6) − (6) chimpanzee
(Pandesa, Pan) +
(2) rhesus monkey (3) − (12) capuchin
monkey (2) +
(9) orangutan (2) − (6) orangutan (Sakura)
+
(7) gorilla (4) + (11) wolves (7) − (9) orangutan (Chantek) + (6) human 22 months
(10) +
(11) dog (7) + (11) wolf (7) − (24) tamarins (4)+
(21) seal (4) + (11) dog (7) +
(21) seal (4) +
(17) dog (14) +
(17) cat (14) +
Distal (10) dolphin (6) + (20) seal (1) + (17) dog (14) + (5) chimpanzee (4) −
(20) seal (1) + (17) cat (14) + (13) dog (2) +
(18) dog (16) + (22) goat (23) +
Cross body (11) wolves (7) − (11) wolf (7) − (14) dog (10) +
(11) dog (7) + (11) dog (7) +
Asymmetric (20) seal (1) + (20) seal (1) +
Momentary At target
Proximal (17) dog (14) +
(17) cat (14) +
(19) wolf (2) −
(19) wolf (2) +
Distal (4) dolphin (Ake) + (20) seal (1) + (3) orangutan (Chantek) +
(20) seal (1) + (3) orangutan (Puti) −
(23) dolphin (2) + (15) dog (10) +
(16) dog (9) +
(17) dog (14) +
(17) cat (14) +
(19) wolf (3) −
(19) wolf (1) +
Cross body (4) dolphin (Ake) + (20) seal (1) + (16) dog (9) +
(20) seal (1) +
(23) dolphin (2) +
Asymmetric (20) seal (1) + (20) seal (1) + (16) dog (9) +
List of references: (1) Anderson et al. 1996; (2) Anderson et al. 1995; (3) Call and Tomasello 1994; (4) Herman et al. 1999; (5) Itakura et al.
1999; (6) Itakura and Tanaka 1998; (7) Peignot and Anderson 1999; (8) Povinelli et al. 1997; (9) Tomasello et al. 1997b; (10) Tschudin et al.
2001;(11)Hareetal.2002;(12)VickandAnderson2000;(13)Hareetal.(1998);(14)HareandTomasello1999;(15)Miklosietal.1998;
(16) Soproni et al. 2002; (17) Mikl
´
osi et al. 2005; (18) McKinley and Sambrook 2000; (19) Mikl
´
osi et al. 2003; (20) Shapiro et al. 2003;
(21) Scheumann and Call 2004; (22) Kaminski et al. 2005; (23) Pack and Herman 2004; (24) Neiworth et al. 2002
Looking at different experimental protocols there is a
considerable variation in the presentation of the pointing
gesture (see Table 1). In humans, pointing is also accom-
panied by joint/mutual visual attention (Morissette et al.
1995) that has been also described for chimpanzees in
semi-natural circumstances (Tomasello et al. 1994). In-
terestingly, however, in order to decrease the chance of
“unconscious” influence on the subjects’ behaviour, inves-
tigators often avoided establishing the state of joint/mutual
attention during pointing. For example, in most experi-
ments by Povinelli and his colleagues (e.g. Povinelli et al.
1997) the experimenter did not establish eye contact with
the subjects (experimenters gazed at the floor) before per-
forming the pointing gesture. In contrast, in other studies,
the experimenter used other visual gestures such as gazing,
that is, simultaneously looking at the bowl when pointing to
their subject (e.g. Itakura et al. 1999). Some experimenters
established eye contact before presenting the pointing ges-
ture (e.g. Soproni et al. 2002).
Experimenters have often varied the movement compo-
nent of the gesture; this can have a strong effect on per-
formance because it can affect salience and can have a dif-
ferential effect on memory. We suggest that the following
categories of arm movements are used for future reference:
Static pointing: The informant is already in the pointing
position (indicating one of the objects) before the subject
views him/her, and remains in this position until the choice
is made.
Dynamic pointing: The pointing gesture is enacted in
full view of the subject and the arm remains in the pointing
position until choice is made.
Momentary pointing: The subject observes only a short
1–2 seconds long extended arm movement toward the ob-
ject, after which the arm rests at the side of the body before
it is allowed to make its choices, therefore the subject has
to remember at which object the arm was pointing.
Experimenters varied also the distance between the point-
ing finger and the object. Although these distances are often
not reported, actually we can deduce the values for most
experiments reviewed here from other distance measures
provided (and assuming that the average length of the hu-
man arm is about 70 cm). Accordingly, we suggest that the
following two categories are considered:
Proximal pointing: The distance between the tip of the
finger and the bowl is smaller than 10–40 cm.
Distal pointing: The distance between the tip of the finger
and the bowl is greater than 50 cm.
Further procedural differences can be found in the spa-
tial relation between the pointer and the objects pointed
at. Generally the pointer stands at equal distance from all
objects (symmetric pointing), but in some cases the exper-
imenter points to a distant object while standing near to
another potential object (asymmetric pointing). Finally, the
ipsilateral hand with regard to the position of the object
or the contralateral one can execute pointings. The later is
usually referred to as cross pointing. (For some schematic
examples of pointing gestures see Fig. 1.)
Fig.1. Schematic viewof the most frequently used pointing gestures
Results
In this section we compare the comprehension of the hu-
man pointing gesture across many species but being aware
of the constraints provided by the data available in the liter-
ature. Because most studies do not only differ in the species
involved, but also in their procedural details, we can not and
do not aim at direct comparisons of the results. Instead, we
compare the outcome of various experiments done with the
same research questions in mind in a qualitative way.
Most of the experiments conducted recently on pointing
comprehension have been summarized in Table 1 under
three different aspects: temporal pattern, spatial relation-
ship to the goal object, and whether pointing was accom-
panied by other forms of visual gesturing (i.e. head turning,
gazing or eye movement).
The human body as a cue for food
In everyday situations the pointer is usually closer to the
object he is indicating, than to other potential objects, and in
the case of captive animals humans are often “the source”
of food, so it can be expected that for such animals the
human body could become a signal for food. In experi-
mental tests, chimpanzees (Itakura et al. 1999), dogs (Hare
and Tomasello 1999) and socialized wolves (Mikl
´
osi et al.
2003) seem to choose the bowl at which the experimenter
is standing, providing a clear indication that they can use
the body position as a cue for choice.
Static and dynamic pointing to proximal
and distal objects
As indicated earlier, two types of pointing gestures can be
discriminated, depending on the distance between the tip
of the finger and the object. Although distance is not an ob-
vious variable for categorization, in some cases “proximal”
and “distal” distances can be distinguished. For example,
objects can be said to be in a proximal position if they are
within reaching distance, and by the same token distant
objects are ‘out of reach’.
The problem of distance between the place of reward and
a visual “beacon” becomes obvious if one considers the
results of earlier similar experiments executed in a social
context with chimpanzees (Jenkins 1943). It was found
that their choice behaviour (in the Wisconsin apparatus) is
poor if the indicating (cuing) object (“beacon”) is further
than 20 cm from the goal object. In contrast the pointing
index finger, head/gaze contour or eyes etc., are usually at
a greater distance from the goal (sometimes even at 1 m).
Therefore one could investigate whether the social context
facilitates the use of distant cues in object choice tasks.
The effect of distance on static pointing in apes can be
seen in Fig 2a. If the distance between the tip of the index
finger and the object was greater than 50 cm, subjects per-
formed poorly in contrast to trials where the pointing finger
almost touched the baited box. We should also note that in
some trials/experiments the pointers also turned their head
and looked in the same direction thereby enhancing the
communicative effect of the gesture but even so the differ-
ence did not disappear. Even after training, chimpanzees in
Povinellietal’s(1997)experimentwerejustabletomaster
Fig. 2. (a) Comparison of the effect of human ‘proximal’ (index
finger is approx. within 10 cm from target) and ‘distal’ (index finger
is approx. more than 50 cm from target) pointing on choice behaviour
in apes. C1: Itakura and Tanaka 1998 (n=2); C2: Itakura et al. 1999
(n=4); O1: Itakura and Tanaka 1998 (n=1); O2: Call and Tomasello
1994 (n=2); P1: Peignot and Anderson 1998 (n=4). Dotted lines
shows chance performance, and ∗ indicates significant difference
from chance. (b) Comparison of the effect of human ‘distal’ pointing
on choice behaviour in different species. D8: Mikl
´
osi et al. 2005
(dogs = 14; cats = 14); D7: Mikl
´
osi et al 2003 (wolves = 4); M1:
Anderson et al. 1996 (n=3); M2: Anderson et al. 1995 (n=3); Do2:
Tschudin et al. 2001 (n=6); S1: Scheumann and Call 2004 (n=4).
Dotted lines shows chance performance, and ∗ indicates significant
difference from chance
the task. Note that in all of these experiments, the exper-
imenter presented a static pointing gesture (keeping the
hand in extended position until the subject made a choice)
that could also increase the chances of success. Two dol-
phins seem to show a much higher level of performance
right from the beginning of such static pointing trials after
being tested on various forms of dynamic pointing gesture
(Pack and Herman 2004).
Capuchin monkeys (Cebus apella) performed well with
proximal dynamic pointing (Anderson et al. 1995; Vick and
Anderson 2000) but three Rhesus macaques were less suc-
cessful in a similar task (Anderson et al. 1996). Recent com-
parative experiments have shown that seals (Scheumann
and Call 2004), dogs and cats (Mikl
´
osi et al. 2005)are
very skillful in trials with proximal dynamic pointing ges-
tures (Fig. 2b) in contrast to chimpanzees (Tomasello
et al. 1997a, b) and wolves (Hare et al. 2002). Dolphins
(Tschudin et al. 2001) have only been tested with the distal
dynamic gesture, and their performance was above chance
in all experiments carried out (Fig. 2b) similarly to one
seal (Shapiro et al. 2003). Cats and dogs (Mikl
´
osi et al.
2005) seemed to be relatively skillful, while wolves tested
by Hare et al. (2002) performed at chance level (see below).
In general, dogs, cats and dolphins performed at a similar
(high) level from the beginning of the testing, so there was
little indication for learning.
It should be noted that the experimenter avoided eye
contact with the dolphins (by wearing sunglasses) but in
trials with dogs, cats and wolves (in some cases with chim-
panzees) eye contact was established before the presen-
tation of the pointing gesture. Comparing dogs and apes
in experiments where eye contact (accompanied by distal
pointing) was obtained before pointing, dogs seem to be
more efficient, but eye contact or especially gaze alterna-
tion, increases the effect of the pointing gesture.
More supporting evidence for comprehension of distal
pointing comes from studies showing that two dogs (Hare
et al. 1998), one dolphin (Herman et al. 1999) and a seal
(Shapiro et al. 2003) were quite skillful at choosing between
two objects that were placed behind them. Interestingly, at
present it seems that despite variations in both the actual
pointing gesture and other accompanying signals, apes have
problems with comprehending static and dynamic distal
pointing gestures in contrast to dogs, cats, dolphins and
seals.
Momentary pointing gestures
The outstretched arm during pointing can be used as a
“beacon” for guiding choice behaviour. Therefore, subjects
can rely on simple spatial orienting mechanisms that are
based on the use of physical cues for finding food repeatedly
at the same location. In the case of momentary pointing
gestures the subject has to remember a short signal for some
time before making a choice. This makes the situation more
similar to a communicative interaction where behaviour of
the receiver is influenced by a short discrete signal emitted
by the sender. Dolphins (Herman et al. 1999; Pack and
Fig. 3. Comparison of the effect of human dynamic and momentary
pointing gestures on choice behaviour. D8: Mikl
´
osi et al. 2005 (
dogs = 14; cats = 14); Do1 (momentary pointing): Herman et al.
1999 (n=1); Do2 (dynamic pointing): Tschudin et al. 2001 (n=6);
S2: Shapiro et al. 2003. ∗indicates significant difference from chance
Herman 2004), dogs, cats (Mikl
´
osi et al. 2005), and a seal
(Shapiro et al. 2003) seem to show only minor decrease in
performance if any (Fig. 3). Currently there is data from
only one ape for this condition, Chantek (an orangutan),
performed well to momentary pointing.
The direction of movement
It can be argued that the signal’s most salient feature is
not the pointing arm, but its direction of movement. This
would explain why some subjects (for example apes) faced
problems when presented with static pointing gestures
(Povinelli et al. 1997). The possibility of such an effect
has been tested by using a “reversed pointing gesture”
when either the experimenter moved away from the goal
object (McKinley and Sambrook 2000) during pointing,
or the pointing arm was lowered to the side of the body
after the static gesture had been observed by the dog
(Soproni et al. 2002). Especially the later variation bears
some importance because in this case the subjects witness
an arm movement opposite to the directional movement
observed in natural circumstances. The performance seems
to affect only partially dogs (Fig. 4) suggesting that the
movement component of the gesture plays a secondary
role in dogs responding to pointing (see also similar results
with dolphins in Pack and Herman 2004).
Asymmetric pointing
The use of asymmetric pointing could be very revealing
because it presents the subject with two conflicting cues.
While animals with more or less human experience show a
clear preference for approaching the object in the vicinity
of the human (see above), in this case, pointing indicates
an object that is further away. In this situation dogs seemed
to prefer to choose the bowl indicated by pointing and not
at which the human was standing (Soproni et al. 2002).
Note that the dogs did not witness the hiding, and the in-
formant stayed in the vicinity of one of the potential places
Fig. 4. Comparison of the effect of movement during pointing
gestures on choice behaviour in dogs. D1: Soproni et al. 2002 (n=9);
D4: Hare et al. 1998 (n=2); D5: McKinley and Sambrook 2000
(n=14). ∗ indicates significant difference from chance
Fig. 5. Comparison of the effect of body signalling and asymmetri-
cal pointing. C2: Itakura et al. 1999 (n=4); C3: Povinelli et al. 1997
(n=7); D1: Soproni et al. 2002 (n=9); D6: Hare and Tomasello 1999
(n=10); S1: Scheumann and Call 2004 (n=4). ∗indicates significant
difference from chance
that could have hidden food. Although this situation proved
to be somewhat difficult for the dogs, they seemed to be
able to overcome their natural tendencies. In a similar man-
ner, asymmetrical pointing seemed to be comprehendible
for seals (Scheumann and Call 2004, Shapiro et al. 2003)
(Fig. 5).
Variability in the form of the pointing gesture
In (adult) humans, the pointing gesture can take many
forms. Although in most cases we point with the extended
arm and index finger ipsilateral to the objects, sometimes,
variations in the position of the upper arm and the hand
with respect to the body can be observed. For example,
pointing across the body represents such a variation when
one is using his contralateral hand. If done with the arm the
extended index finger usually protrudes on the contralat-
eral side of the body (cross-pointing). Rarely, people point
with a bent arm when the elbow protrudes on the ipsilateral
side of the body and the index finger is positioned in front
of the belly (described as “elbow cross-pointing”: Soproni
et al. 2002; or as “belly pointing” in Hare et al. 1998).
The use of such (relatively) unfamiliar variations of the
Fig. 6. Comparison of the effect of human ‘cross-pointing’ and
‘elbow cross-pointing’ on choice behaviour. D1: Soproni et al. 2002
(n=9); D4: Hare et al. 1998 (n=2); D6: Hare and Tomasello 1999
(n=10); Do1: Herman et al. 1999 (n=1); S2: Shapiro et al. 2003
(n=1); C3: Povinelli et al. 1997 (n=7). ∗ indicates significant differ-
ence from chance
pointing gesture offers the possibility to test the animal’s
plasticity and capacity for generalization in understanding
this visual signal. We should also add that during point-
ing interactions under natural conditions, animals have the
opportunity to observe the gesture from different viewing
angles that might also contribute to their flexibility in re-
sponding to unfamiliar signals.
The cross pointing gesture was so far only applied to
dogs (Soproni et al. 2002), dolphins (Pack and Herman
2004) and a seal (Shapiro et al. 2003); all demonstrated
relatively good levels of comprehension (Fig. 6). However,
since in the cross pointing gesture, the tip of the index
finger is even further from the object than in the case of
the normal pointing gesture, then apes should show on the
basis of previous experience even lower performance.
For the “elbow-cross-pointing” gesture there are data
both for apes and dogs (Fig. 6), and members of both
species seem to be unable to comprehend the meaning of
pointing which is less surprising in the case of apes given
their low performance with other types of the pointing ges-
ture. In the case of dogs, it seems that the protrusion of
the hand/finger from the body torso represents the most
characteristic feature of the pointing gesture. Interestingly,
recent results suggest that seals show decreased perfor-
mance when only the index finger is used for indicating the
correct container (Scheumann and Call 2004) but another
seal might be better with such type of gestures (Shapiro
et al. 2003). Finally, in a somewhat different design, dol-
phins seem to be able to follow the direction at which the
hand was pointing and not at which the arm was extended
(see Fig. 4b in Pack and Herman 2004)
The role of additional attention cues
In humans, pointing is usually accompanied with gazing
cues that direct the attention of the subject both to the
signaller and the target. In some cases, researchers tried
to separate the pointing gesture from these natural human
specific features by avoiding gazing at the animal. The
performance of dolphins and a seal was not affected. In-
terestingly however, chimpanzees showed improvement if
the human was also gazing at the target but not if he was
gazing at the chimpanzee during pointing (Povinelli et al.
1997). This can be explained on the basis of gaze following
in the chimpanzees (e.g. Povinelli and Eddy 1996), when
human’s directional gazing biases the choice behaviour.
In some experiments pointing was accompanied with re-
peated gaze alternations when the human was looking to
and from between the subject and the target. This “en-
hanced” or facilitated version of pointing increased the
performance of two enculturated chimpanzees (Itakura and
Tanaka 1998) in the case of proximal pointing. Goats with
restricted human experience performed just above chance
level in this case, when additionally to pointing, many
other behavioural cues indicated the location of the tar-
get (Kaminski et al. 2005). Little variation can be detected
in this regard in dogs but they have not been tested without
gazing, and there is some indication that dogs could even
decrease their performance if the gazing cue is omitted
(personal observations).
The effect of human social experience and development
The comparison of comprehension in these species is in-
variably confounded by the effect of experience with hu-
mans, and it can be argued that different individual experi-
ence can have a larger effect on this behaviour than species
predisposition. For example, dogs live usually and natu-
rally in a relatively stable social environment in or around
human families. Their experience with and exposure to the
pointing gesture can be compared to that of children since
it should be remembered that dogs often share to some
extent the physical and social environment. Although dol-
phins are kept in a different manner, the living environment
of the animals used in these studies is relatively similar
including their level of intensity of interaction with hu-
mans. The captive apes represent the most diverse group
because their contact with humans is often restricted to
some extent (or after some age), and their direct contact
with humans is difficult to assess. Some individuals were
captured in the wild, while others were raised in special
nurseries or in human homes, and differences in early so-
cial experience might turn out to be important. The no-
tion of enculturation refers to apes that were brought up
with intensive human contact (Call and Tomasello 1996),
and although this concept might have explanatory value in
some cases (e.g. imitation, see Carpenter et al. 1995; Nagell
et al. 1993), the lack of quantification of human experience
often makes it difficult to apply (see also Bering 2004;
Tomasello and Call 2004). Nevertheless one might argue
that more intense human contact leads to better compre-
hension of the pointing gesture. Unfortunately, the present
data does not equivocally support such a conclusion. Seven
nursery reared chimpanzees in the study by Povinelli et al.
(1997) reached about 100% performance with the proxi-
mal pointing gesture after some training which is compara-
ble to the two “enculturated chimpanzees” in the study by
Itakura and Tanaka (1998). Similarly, captive lowland go-
rillas with little human contact proved to be successful with
static proximal pointing (Peignot and Anderson 1999). In
contrast,mostapesusedinbothstudiesbyTomaselloetal.
(1997a, b) and Itakura et al. (1999) did not show signs of
comprehension.
Individuals that acquired communicative skills in close
contact and in the course of communicative exchanges with
humans (i.e. language trained apes) did not show outstand-
ing performance. There are data that Chantek (language
training, see Miles 1990) was reported to choose rela-
tively well in the case of distal pointing gestures (Call and
Tomasello1994)butSavage-Rumbaugh(1986)notesthat
two language trained apes showed little comprehension of
human pointing (no formal testing has been reported).
The comparison of dogs and wolves has revealed that in
some cases even extensive socialization with humans can-
not overcome natural species differences but can increase
performance after some training. In a recent study, dogs
and wolves were raised under identical social conditions in
close human contact during their first 3–4 months of life
(Mikl
´
osi et al. 2003). Testing them under identical circum-
stances revealed that juvenile dogs performed better than
wolves of the same age but that after extensive training,
one wolf was able to reach a performance comparable to
that of dogs even with the momentary distal gesture.
Earlier there was some indication that social experience
improves the performance of dogs to pointing gestures
(Hare and Tomasello 1999). However, there are observa-
tions that dogs as young as 4 months old are able to choose
correctly on the basis of static, proximal pointing gesture
(Hare et al. 2002) even if raised in puppy kennels with lim-
ited human contact. More recent observations suggest that
at this age, dogs living in human homes perform relatively
well even with momentary distal pointing gestures (G
´
acsi
et al. 2005, unpublished data).
Discussion
Functional arguments: Can a single ultimate
hypothesis explain species differences
in comprehension of pointing?
Recently, arguments have been put forward to explain the
apparent differences between apes and humans suggest-
ing that the inherently competitive social strategy of pri-
mates prohibits them from performing well in a cooperative
context (Hare 2001). In humans, communication based on
pointing is inherently cooperative in its nature. The infor-
mant directs the attention of the perceiver to himself and/or
to the gesture, and this signalling is seen usually as a benefit
for the observer.
However, the concept of cooperation can also be evoked
on another level. For example, the “social tool use” hy-
pothesis of this gesture is based on the observation that the
perceiver is usually willing to act in partnership with the
pointer’s goal. From the pointer’s perspective it might be
either a natural tendency to expect this (G
´
omez 1990)or
a result of experience (learning) during social interactions.
Many recent studies do not support a high-level interpreta-
tion of cooperation among apes (e.g. Boesch and Boesch
1989; Chalmeau and Gallo 1993), nevertheless this kind of
‘social tool use’ has been observed both in apes (G
´
omez
1990) and dogs (Mikl
´
osi et al. 2000) while interacting with
humans.
In support of the aforementioned hypothesis chim-
panzees have been found to be superior in judging the
visual experience of the other individual (conspecific) in
agonistic (e.g. Hare et al. 2000) but not in cooperative situ-
ations (Povinelli et al. 1990), suggesting that chimpanzees
are experiencing difficulties in understanding tasks based
on cooperation. This notion could receive further support
from the observation that chimpanzees do not actively share
food although they tolerate passive sharing (de Waal 1989)
and the lack of this natural habit could prevent them from
understanding the “logic” of interactions based on pointing.
However, the picture becomes less clear if the
“cooperation-competition hypothesis” is applied to other
species. Hare and Tomasello (1999) noted that the hunt-
ing behaviour of the wolves relies more on cooperative
abilities in comparison with the apes. This would suggest
that both wolves and dogs should be able to perform well
in responding to the pointing gesture, provided they have
appropriate social experience and/or training. However, as
we have seen this is not the case because even after ex-
tended human socialization wolves’ performance was in-
ferior to that of dogs (Mikl
´
osi et al. 2003). Furthermore,
chimpanzees (Itakura and Tanaka 1998) and monkeys (
Vick and Anderson 2000) learned to comprehend simpler
forms of the pointing gestures, and at the behavioural level
(although no such data are available) most chimpanzee sub-
jects seem to be able to cooperate with their human partner
during the task. Conversely, one could argue that in the
case of proximal pointing the informant is within reach of
the potential food source (e.g. in the case of standing at the
target), therefore the situation is not cooperative at all, and
the gesture becomes a cue (and not a signal, see Hauser
1996) for indicating either the place of the food or the goal
of the “dominant” human to obtain the food.
Although the “cooperation-competition hypothesis” can
explain why dolphins showing many instances of coopera-
tive behaviour (e.g. Connor and Norris 1982) exhibit supe-
rior pointing comprehension (Herman et al. 1999) it fails
short in the case of seals that are not particularly cooperative
in their nature (Le Boeuf et al. 2000; McConell et al 1999).
This means that although the “cooperation-competition hy-
pothesis” might have some virtue in explaining differences
within the primate line, such difference in predominant so-
cial strategies could only partially be responsible for the
observed effect.
Having noted high levels of pointing comprehension
in dogs, another appealing hypothesis aims at explaining
dog-ape differences by the effect of domestication (Hare
et al. 2002; Mikl
´
osi et al. 1998, 2000; Soproni et al. 2001,
2002). It has been suggested that dogs have been selected
for enhanced sociocognitive abilities for living in human
social settings. However, it should be noted that domesti-
cation is not a unified process and the behaviour selected
for depends not only on the selection process, but also
on the species in question, and there is likely a “selection
response x species” interaction. For example, dogs and
cats are among the animals domesticated very early. Being
both predatory species, dogs and cats share many cognitive
abilities but it is likely that their domestication took place
in context and species differences in their communicative
behaviours toward humans is also evident (Mikl
´
osi et al.
2005). A recent finding that domesticated goats with
relatively little human contact also seem to be able to
master the comprehension of pointing gestures (Kaminski
et al. 2005), provides further support for the domestication
hypothesis but it remains to be seen whether all species
domesticated perform better in these tasks in comparison
to their “wild cousins” if the later are socialized to humans
at comparable levels. The only available case of dog-wolf
comparison points in this direction.
Despite the appealing nature of the domestication hy-
pothesis, it still fails to explain pointing comprehension in
dolphins and seals, but it could be suggested that species
with some exapted behavioural traits (see Gould and Vbra
1982) for using directional signals in their species specific
communicative exchanges, are able to comprehend the hu-
man pointing gesture, given some social experience or for-
mal training (see also Hare and Tomasello 1999;Herman
et al. 1999). More specifically, explaining comprehensive
abilities of their dolphin, Herman et al. (1999) suppose that
the oriented body position of the dolphins during projection
of the sonar emission could provide a behavioural basis for
such ability. A non-echolocating observer dolphin is able
to identify a target that was targeted by another dolphin by
its sonar (Xitco and Roitblat 1996). Translated to the world
of visual senses this means that a dolphin is able to attend
to an object the other is looking at.
Similarly, wolves have the ability to signal the direction
where potential prey can be located (Mech 1970). When
sensing the smell of the prey, wolves often freeze into a
“pointing” position for some time. (This behaviour seems
to have a genetic basis, and has been enhanced by selective
breeding in some hunting dog breeds, i.e. pointers). How-
ever, the ability to follow the other’s gaze into a space is
not restricted to dogs and dolphins because chimpanzees
have been found to use the gazing cues in very flexible
ways (Hare et al. 2000; Povinelli and Eddy 1996). There-
fore it seems unlikely that the ability of gaze following
(which seems to be present in most mammals investigated
so far) would give a primary basis for the comprehension
of pointing.
Finally, it should be noted that the evolutionary and func-
tional hypotheses listed above are not mutually exclusive
and depending on the species they might have a synergic or
antagonistic effect. At present is seems unlikely that point-
ing comprehension (or the lack of it) can be explained by a
simple one factorial theory.
Mental representations behind pointing comprehension
Recently, it has been argued that all experimental evidence
gathered so far on pointing comprehension in animals can
be explained by “simple conditioning processes” (Shapiro
et al. 2003). This opinion is in concert with Povinelli’s
“low level”hypothesis, which explains performance in such
communicative situations by assuming that low level asso-
ciative learning is at work. Especially in the case of social
cognition it has become a fashion to think about the animal
mind dichotomously: either assuming “simple condition-
ing” or some “high level complex cognitive processes”.
However, it becomes extremely clear that by putting ac-
tual performance in one or the other category not much is
explained. Actually, it turns out that such “simple condi-
tioning” can be quite a complex process in itself. In this
regard, we sympathize with the approach taken by Call
(2001) who places more emphasis on explaining how an-
imals set up general rules after experiencing certain envi-
ronmental invariance. However, this line of investigation
needs carefully planned studies based on viable hypothe-
ses with appropriate control conditions. For example, the
comparison of responses to proximal and distal pointing
gestures could provide bases for differentiating between
asocial and social aspects of the task. In the case of the
former, the pointing finger/hand is at the goal object and
learning about this form of gesture can be restricted to as-
sociating the vicinity of the cue with the place of food.
The performance with distal pointing gestures cannot be
explained easily this way because animals do not readily
associate physical cues placed at a distance from the rein-
forced location (see above, Jenkins 1943). In this case, they
rely either on the movement of the hand at the beginning of
the cueing (see contradictory data for dogs in Soproni et al.
2002), or they have other strategies associated only with
social interactions and not asocial situations. Additionally
we find striking differences among species in performance
with distal pointing as socialized wolves or chimpanzees
have been found to have problems in understanding the
task. Such negative evidence suggests that learning expe-
rience in itself is not enough to develop this skill. There is
little doubt that associative learning plays a role in com-
prehending a gesture of a heterospecific, but the question
is how flexible such learning mechanisms are and what
kind of representations emerge as a consequence. The use
of novel communicative gestures can also be informative
here. Tomasello et al. (1997a, b) found that in contrast to
children, chimpanzees had problems to recognize the act of
putting an object on the baited bowl as signalling the place
of food, while dogs seemed to be able to base their choice
on this signal (Agnetta et al. 2000). This provides further
evidence that the representations acquired by dogs and chil-
dren in communicative context with humans might share
some features in contrast to those emerging in some apes.
Another mechanism playing a role has been suggested
by Mikl
´
osi et al. (2003) after observing the behaviour of
socialized wolves and dogs in problem situations. It was
found that dogs engage more readily in gazing contact with
humans than wolves and along with others (Byrne 2003),
we have argued that this propensity might facilitate the
development of dog-human communicative interactions.
A further question is whether animals represent and are
able to decode the referential information provided by the
pointing gesture, which is an important ability in humans
(e.g. Tomasello and Camaioni 1997). In view of Povinelli
et al. (1997), the comprehension of the referential nature of
the pointing gesture means understanding that it refers to (or
is about) a given object in space. Their tests were based on
the presumption that the ability to generalize from the basic
(proximal) pointing gesture to novel forms of the point-
ing gesture might reveal representational understanding in
chimpanzees. In contrast to the (often) negative findings
with chimpanzees, both dogs and dolphins displayed high
levels of performance in the case of some novel pointing
gestures. The application of Povinelli’s argument would
suggest that both latter species might share some under-
standing with humans on the referential character of the
pointing gesture. Herman et al. (1999) broadened the quest
for referentiality showing that in dolphins the pointing ges-
ture could also be a substitute for other gestural symbols
referring to objects. Of course, it is difficult to exclude that
the trained dolphin had no prior experience with pointing
of this kind during their interaction with humans. Neverthe-
less, the dolphin was able to substitute the pointing, cross
pointing and combinations of points and cross-points for
the symbols in an artificial symbolic gestural system. A
major thrust of the combination of the point test was to
show that the subject could understand a reference to an
object that was to be acted upon indirectly (the destination
object) which had to be represented in the memory while
the transport object was identified and transported. Fur-
ther evidence for referentiality comes from experiments in
which a dolphin shows the ability to choose successfully
from three or more objects on a horizontal plain on the
basis of pointing. In the case of the dog, we do not have
such evidence yet, but dogs responding to other novel types
of pointing gestures could give more support to this idea
(Mikl
´
osi et al., in preparation).
The effect of experience and socialization
Given the peculiarities of the phenomenon, the experience
with humans could turn out to be crucial. Unfortunately
the picture is not clear because no systematic compar-
isons have been done. For example, language trained apes
should display superior abilities if daily, communicative
exchange is an important factor in pointing comprehen-
sion. To date, only Chantek has been tested systemati-
cally and evidence from other individuals is contradic-
tory (see above). Similarly in the case of wolf-dog com-
parison, human socialization did not result in comparable
performances.
Interestingly, after learning to point to the hiding place,
macaques have shown increased understanding of the hu-
man pointing gesture (Blaschke and Ettlinger 1987) and
conditioned joint attention in the same species, seems to fa-
cilitate comprehension of pointing (Kumashiro et al. 2003).
Both results suggest the functioning of a more complex
mental representational system behind such comprehension
than one would assume on the basis of simple associative
phenomena.
Nevertheless it is likely that a minimal experience with
humans is needed to perform successfully and extensive
experiences can faceplate performance in some cases, espe-
cially when the subject is faced with unfamiliar situations.
Future directions
Perhaps at this point we should admit that this review was
elicited by our frustration in trying to make sense of recent
experimental results in this field. Moreover, in the field of
social cognition, we often note that researchers “pick” their
favourite arguments and totally disregard the actual results
of the experiments and their external validity. On this basis
we agree with one of our reviewers saying that the present
state of this field does not allow for scientific arguments on
social cognitive evolution. In this sense, this work should
be treated as a provocative script providing a “mirror” to
all those involved. We hope, however, that by summarizing
most of the available data we facilitate better-planned re-
search strategies and more systematic experiments. A short
list suggesting the most urgently needed studies follows.
Technical considerations:
(1) We have suggested a kind of categorisation of the ges-
tures, but there is room for improvement. This would
help to understand how the gesture was actually exe-
cuted and what the subject saw. Apparently there are
cultural differences among humans, which cause no
major problems in our conspecific communication, but
might do make a difference if not controlled for in
experimental conditions.
(2) The so-called probe procedure seems to be accepted
by most laboratories. Although this makes life easier
to account for the effect of generalization, researchers
should provide data on first trials with the novel gesture
and also show whether learning takes place over the
testing procedure.
(3) As many assume that social experience is important,
data on experience with humans should be provided. In
the case of species comparison, members of all species
should experience similar level of human contact, tak-
ing into account developmental effects. This problem
is most evident in the case of ape-human comparison
when the performance of apes is compared to young
children. In principle differences in the results could
always be attributed to differential social experience.
Suggestions for further research:
(1) Using monkey species that are known to differ in
their social relationships, one can test the cooperative-
competitive hypothesis further. For example, coop-
erative behaviour observed in captivity of Tonkean
(Macaca tonkeana) and Rhesus macaques (M. mu-
latta) seem to mirror their dominance structure in the
wild (Petit et al. 1992). Socialized Tonkean macaques
should be superior to Rhesus monkeys if social toler-
ance and cooperative nature contributes to better per-
formance in pointing tasks.
(2) The domestication hypothesis needs further parallels
when both wild and domesticated species are tested
in comparable manner (e.g. pigs versus wild boars).
It should be emphasized that in this case the experi-
ence both with humans and the experimental procedure
should be the same for both species. Positive results
could encourage direct comparison between domesti-
cated species that originate from species of similar eco-
logical background, as in dogs and cats or goats and
horses. Accordingly, “domesticated” foxes (Trut 1999)
should perform also better than non-domesticated ones
when tested with distal pointing gestures (see also Hare
et al. 2002) because this type of gesture proved very
difficult to learn by socialized wolves (Mikl
´
osi et al.
2003).
(3) Interestingly, there are only a few studies with human
children (i.e. Povinelli et al. 1997). Recently, we have
started to re-run experiments in dogs with children in
order to collect data on their development of pointing
comprehension (Soproni 2004).
(4) One should investigate whether other faculties of social
cognition can influence understanding of pointing. For
example, does the ability of establishing joint attention,
the sensitivity for attention cues (G
´
acsi et al. 2004;
Xitco et al. 2004) or the skill of pointing, enhance
pointing comprehension?
Acknowledgements This work has been supported by an OTKA
grant (T043763) and grant of the Hungarian Academy of Sciences
(F01/031). We are grateful to Josep Call and J
´
ozsef Top
´
al and two
anonymous reviewers for providing valuable suggestions and con-
structive criticism on earlier versions of this paper
References
Agnetta B, Hare B, Tomasello M (2000) Cues to food locations that
domestic dogs (Canis familiaris)ofdifferentagesdoanddo
not use. Anim Cogn 3:107–112
Allen C, Saidel E (1998) The evolution of reference. In Dellarosa
DC, Allen C (eds) The evolution of mind. Oxford University
Press, New York, pp 183–203
Anderson JR, Sallaberry P, Barbier H (1995) Use of experimenter-
given cues during object-choice tasks by capuchin monkeys.
Anim Behav 49:201–208
Anderson JR, Montant M, Schmitt D (1996) Rhesus monkeys
fail to use gaze direction as an experimenter-given cue in an
object-choice task. Behav Proc 37:47–55
Bates E, Benigni L, Bretherton I, Camaioni L, Volterra V (1977)
From gesture to the first word: On cognitive and social
prerequisites. In M Lewis, L Rosenblum (eds) Interaction,
conversation, and the development of language. Wiley:
New York
Bering JM (2004) A critical review of the “enculturation hypothe-
sis”: The effects of human rearing on great ape social cognition.
Anim Cogn 7:201–213
Blaschke M, Ettlinger G (1987) Pointing as an act of social
communication by monkeys. Anim Behav 35:1520–1523
Boesch C, Boesch H (1989) Hunting behaviour of wild chim-
panzees in the Tai Forest National Park. Am J Phys Anthr 78:
547–573
Byrne RW (2003) Animal communication. What makes a dog able
to understand its masters? Current Biology, 13:R347–R348
Call J (2001) Chimpanzee social cognition. Trends Cogn Sci
5:388–393
Call J, Tomasello M (1994) Production and comprehension of
referential pointing by orangutans (Pongo pygmaeus). J Comp
Psych 108:307–317
Call J, Tomasello M (1996) The effect of humans on the cognitive
development of apes. In: Russon AE, Bard KA, Parker ST (eds),
Reaching into thought: The minds of the great apes. Cambridge
University Press, Cambridge, pp 371–403
Candland DK (1993) Feral children and clever animals. Oxford
University Press, New York
Carpenter M, Tomasello M, Savage-Rumbaugh S (1995) Joint
attention and imitative learning in children, chimpanzees and
enculturated chimpanzees. Soc Devel 4:217–237
Chalmeau R, Gallo A (1993) Social constrains determine what is
learned in the chimpanzee. Behav Proc 28:173–180
Connor RC, Norris KS (1982) Are dolphins reciprocal altruists? Am
Nat 119:358–374
Evans CS (1997) Referential signals. In: Owings DH, Beecher
MD, Thompson NS (eds.): Perspectives in Ethology, vol 12,
Communication, Plenum Press, New York, pp 99–143
G
´
acsi M, Mikl
´
osi A, Varga O, Top
´
al J, Cs
´
anyi V (2004) Are readers
of our face readers of our minds? Dogs (Canis familiaris)show
situation-dependent recognition of human’s attention. Anim
Cogn 7:144–153
G
´
omez JC (1990) The emergence of intentional communication
as a problem solving strategy in the gorilla. In: Parker TS,
Gibson KR (eds), “Language” and intelligence in monkeys
and apes: Comparative developmental perspectives. Cambridge
University Press, Cambridge, pp 333–355
Gould SJ, Vbra ES (1982) Exaptation – a missing term in the science
of form. Paleobiol 8:4–15
Hare B (2001) Can competitive paradigms increase the validity of ex-
periments on primate social cognition? Anim Cogn 4:269–280
Hare B, Call J, Tomasello M (1998) Communication of food location
between human and dog (Canis familiaris). Evol Commun
2:137–159
Hare B, Tomasello M (1999) Domestic dogs (Canis familiaris)use
human and conspecific social cues to locate hidden food. J
Comp Psychol 113:173–177
Hare B, Call J, Agnetta B, Tomasello M (2000) Chimpanzees know
what conspecifics do and do not see. Anim Behav 59:771–785
Hare B, Brown M, Williamson C, Tomasello M (2002) The
domestication of cognition in dogs. Science 298:1634–1636
Hauser M (1996) The evolution of communication. MIT Press,
Cambridge Mass
Herman LM, Abichandani SL, Elhajj AN, Herman EYK, Sanchez
JL, Pack AA (1999) Dolphins (Tursiops truncatus) comprehend
the referential character of the human pointing gesture. J Comp
Psychol 113:347–364
Itakura S, Tanaka M (1998) Use of experimenter given cues
during object-choice tasks by chimpanzees (Pan troglodytes),
an orangutan (Pongo pygmaeus), and human infants (Homo
sapiens). J Comp Psychol 112:119–126
Itakura S, Agnetta B, Hare B, Tomasello M (1999) Chimpanzee use
of human and conspecific social cues to locate hidden food.
Devel Sci 2:448–456
Jenkins WO (1943) A spatial factor in chimpanzee learning. J Comp
Psychol 35:81–84
Kaminski J, Riedel J, Call J, Tomasello M (2005) Domestic goats
(Capra hircus) follow gaze direction and use some social cues
in an object choice task. Anim Behav 69: 11–18
Kumashiro M, Ishibashi H, Uchiyama Y, Itakura S, Murata A,
Iriki A (2003) Natural imitation induced by joint attention in
Japanese monkeys. Int J of Psychophysiol 50:81–99
Leavens AD, Hopkins WD (1999) The whole-hand point: The struc-
ture and function of pointing from a comparative perspective.
J Comp Psychol 113:417–425
Le Boeuf BI, Crocker DE, Costa DP, Blackwell SB, Webb PM,
Houser DS (2000) Foraging ecology of Northern elephant seals.
Ecol Monogr 70:353–382
McConell BJ, Fedak MA, Lovell P, Hammond PS (1999) Movements
and foraging areas of grey seals in the North-sea. J Appl Ecol
36:573–590
McKinley J, Sambrook TD (2000) Use of human given cues by
domestic dogs (Canis familiaris) and horses (Equus caballus).
Anim Cogn 3:13–22
Mech LD (1970) The wolf: The ecology and behaviour of an
endangered species. Natural History Press, New York
Mikl
´
osi
´
A, Polg
´
ardi R, Top
´
al J, Cs
´
anyi V (1998) Use of experimenter
given cues in dogs. Anim Cogn 1:113–121
Mikl
´
osi
´
A, Polg
´
ardi R, Top
´
al J, Cs
´
anyi V (2000) Intentional
behaviour in dog-human communication: An experimental
analysis of ‘showing’ behaviour in the dog. Anim Cogn 3:
159–166
Mikl
´
osi A, Kubinyi E, Top
´
al J, G
´
acsi M, Vir
´
anyi Z, Cs
´
anyi V (2003)
A simple reason for a big difference: Wolves do not look back
at humans but dogs do. Curr Biol 13:763–766
Mikl
´
osi
´
A, Pongr
´
acz P, Lakatos G, Top
´
al J, Cs
´
anyi V (2005) A
comparative study of dog-human and cat-human interactions in
communicative contexts. J Comp Psych 119: 179–186
Miles HLW (1990) The cognitive foundations for reference in a
signing orangutan. In: Parker TS, Gibson KR (eds), “Language”
and intelligence in monkeys and apes: Comparative develop-
mental perspectives. Cambridge University Press, Cambridge,
pp 511–539
Morissette P, Ricard M, Decarie TG (1995) Joint visual attention and
pointing in infancy: A longitudinal study of comprehension. Br
J Dev Psych 13:163–175
Nagell K, Olguin RS, Tomasello M (1993) Process of social learning
in the tool use of chimpanzees (Pan troglodytes) and human
children (Homo sapiens). J Comp Psychol 107:174–186
Neiworth JJ, Burman MA, Basile BM, Lickteig MT (2002) Use
of experimenter-given cues in visual co-orienting and in an
object-choice task by a new world monkey species, cotton top
tamarins (Saguinus oedipus). J Comp Psychol 116: 3–11
Owren MJ, Rendall D (1997) An affect-conditioning model of
nonhuman primate vocalizations. In: Owings DW, Beecher
MD, Thompson, NS (eds), Perspectives in Ethology, Vol. 12
Communication. Plenum Press. New York, pp. 299–346
Pack AA, Herman LM (2004) Bottlenosed dolphins (Tursiops
trunctaus) comprehend the referent of both static and dynamic
human gazing and pointing in an object-choice task. J Comp
Psychol 118:160–171
Peignot P, Anderson JR (1999) Use of experimenter given manual
and facial cues by gorillas (Gorilla gorilla) in an object-choice
task. J Comp Psychol 113:253–260
Petit O, Desportes C, Thierry B (1992) Differential probability of
co-production in two species of macaque (Macaca tonkeana,
Mmulatta). Ethology 90:107–120
Pfungst O (1911) Clever Hans, the horse of Mr. von Osten. Henry
Holt, New York
Povinelli DJ, Nelson KE, Boysen ST (1990) Inferences about
guessing and knowing by chimpanzees (Pan troglodytes). J
Comp Psychol 104:203–210
Povinelli DJ, Reaux JE, Bierschwale DT, Allain AD, Simon BB
(1997) Exploitation of pointing as a referential gesture in
young children, but not adolescent chimpanzees. Cogn Devel
12:423–461
Povinelli DJ, Bierschwale DT, Cech CG (1999) Comprehension of
seeing as a referential act in young children, but not juvenile
chimpanzees. Br J Devel Psychol 17:37–60
Povinelli DJ, Eddy TJ (1996) Chimpanzees: Joint visual attention.
Psych Sci 7:129–135
Povinelli DJ, Giambrone S (1999) Inferring other minds: Failure of
the argument by analogy. Philosophical Topics 27:167–201
Rosenthal R (1965) Clever Hans (the Horse of Mr Osten) by Oskar
Pfungst. Henry Holt, New York
Savage-Rumbaugh SE (1986) Ape language: From conditioned
response to symbol. Columbia University Press, New York
Scheumann M, Call J (2004) The use of experimenter given cues by
South African fur seals (Arctocephalus pusillus). Anim Cogn
7:224–231
Shapiro AD, Janik VM, Slater PJB. (2003) Gray seal (Halichoerus
grypus) pup responses to experimental-given pointing and
directional cues. J Comp Psychol 117:355–362
Soproni K (2004) Gestural communication between dog and man.
(Phd thesis, E
¨
otv
¨
os University, Budapest, in Hungarian)
Soproni K, Mikl
´
osi
´
A, Top
´
al J, Cs
´
anyi V (2001) Comprehension of
human communicative signs in pet dogs (Canis familiaris). J
Comp Psychol 115:122–126
Soproni K, Mikl
´
osi
´
A, Top
´
al J, Cs
´
anyi V (2002) Dogs’ (Canis
familiaris) responsiveness to human pointing gestures. J Comp
Psychol 116:27–34
Tinbergen N (1963) On and methods of ethology. Z Tierpsych
20:410–433
Tomasello M, Call J, Nagell K, Olguin R, Carpenter M (1994) The
learning and use of gestural signals by young chimpanzees: A
trans-generational study. Primates 35:137–154
Tomasello M, Call J, Hare B (1997a) Five primate species follow
the visual gaze of conspecifics. Anim Behav. 55:1063–1069
Tomasello M, Call J, Gluckman A (1997b) Comprehension of novel
communicative signs by apes and human children. Child Devel
68:1067–1080
Tomasello M, Camaioni L (1997) A comparison of the gestural com-
munication of apes and human infants. Human Devel 40:7–24
Tomasello M, Call J (2004) The role of humans in the cognitive
development of apes revisited. Anim Cogn 7:213–216
Trut LN (1999) Early canid domestication. The farm fox experiment.
Am Scientist 87:160–169
Tschudin A, Call J, Dunbar RIM, Harris G, van der Elst C (2001)
Comprehension of signs by dolphins (Tursiops truncatus). J
Comp Psychol 115:100–105
Vea JJ, Sabater-Pi J (1998) Spontaneous pointing behaviour in
the wild pygmy chimpanzees (Pan paniscus). Folia Prim
69:289–290
Vick S, Anderson JR (2000) Learning and limits of use of eye gaze
by capuchin monkeys (Cebus apella) in an object-choice task.
J Comp Psychol 114:200–207
Waal F de (1989) Food sharing and reciprocal obligations among
chimpanzees. J Human Evol 18:433–459
Xitco MJ Jr, Roitblat HL (1996) Object recognition through
eavesdropping: Passive echolocation in bottlenose dolphins.
Anim Learn Behav 24:355–365
Xitco MJ, Gory JD, Kuczaj SA (2004) Dolphin pointing is linked to
the attention behaviour of a receiver. Anim Cogn 7:231–238
