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Dogs distinguish human intentional and unintentional action
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* Published: 01 September 2021
Dogs distinguish human intentional and unintentional action
* Britta Schunemann ORCID: orcid.org/0000-0002-7493-5904^1^ na1,
* Judith Keller^1,2^ na1,
* Hannes Rakoczy^1,
* Tanya Behne^1 &
* Juliane Brauer^3,4
Scientific Reports volume 11, Article number: 14967 (2021) Cite this
article
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Subjects
* Animal behaviour
* Social evolution
Abstract
When dogs interact with humans, they often show appropriate reactions
to human intentional action. But it is unclear from these everyday
observations whether the dogs simply respond to the action outcomes
or whether they are able to discriminate between different categories
of actions. Are dogs able to distinguish intentional human actions
from unintentional ones, even when the action outcomes are the same?
We tested dogs' ability to discriminate these action categories by
adapting the so-called "Unwilling vs. Unable" paradigm. This paradigm
compares subjects' reactions to intentional and unintentional human
behaviour. All dogs received three conditions: In the
unwilling-condition, an experimenter intentionally withheld a reward
from them. In the two unable-conditions, she unintentionally withheld
the reward, either because she was clumsy or because she was
physically prevented from giving the reward to the dog. Dogs clearly
distinguished in their spontaneous behaviour between unwilling- and
unable-conditions. This indicates that dogs indeed distinguish
intentional actions from unintentional behaviour. We critically
discuss our findings with regard to dogs' understanding of human
intentional action.
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Introduction
When humans interact with other humans, this interaction depends to a
substantial extent on ascribing intentions to one another. We could
hardly make sense of other agents' actions if we could not consider
what the agent planned and whether he or she acted intentionally or
accidentally^1,2. The concept of intention is a central part of our
Theory of Mind, the ability to attribute mental states to others and
ourselves^3. Theory of Mind has long been regarded as a uniquely
human ability. However, while this may be true for our full-fledged
adult Theory of Mind that includes the ascription of complex
subjective states, accumulating evidence suggests that certain basic
capacities to ascribe simple mental states to other agents are
present in some non-human species, such as apes and birds. For
example, chimpanzees track whether other agents can or cannot see a
given scene^4,5, and male Eurasian jays react appropriately to a
females' desires even if they do not share these desires^6 (for an
overview see^7,8,9). In human ontogeny, the ascription of intentions
is one of the primary forms of Theory of Mind: Even infants
understand actions as goal-directed^10, differentiate intentional
from unintentional behaviour^11,12, and rationally imitate failed
actions^13.
But humans are not the only ones who rely substantially on making
sense of human actions. The dog is probably the animal whose history
and everyday life are most interwoven with that of humans. Having
evolved in close proximity to humans, dogs have developed special
skills for forming close social bonds with us^14,15,16. In this close
relationship, they are confronted with different forms of human
intentionality on a regular basis, for instance communicative
intentions, when humans either intend or do not intend to communicate
with them using certain behavioural and vocal cues^17. Also, dogs
experience how humans direct their actions to certain goals, and
encounter intentional and unintentional actions, for instance, when
humans lie on the grass intentionally versus when they trip.
But do dogs show appropriate responses to human intentional actions
because they are simply responding to an action's environmental
outcome or because they actually recognize the human's intention? In
cases where an intention has been realized successfully it is hard to
tell whether dogs react to the action's outcome or to the underlying
intention. Accordingly, the methodological approach to study
intentions in both human and non-human animals has been to examine
their responses to failed attempts and accidental behavior^12,18,19,
20,21,22,23. To our knowledge this approach has not been used with
dogs, yet.
There is ample research on dogs' capacity to react appropriately to
humans' mental states: Dogs register a human's attentive state when
they decide whether to steal food^24, to beg for food^25, or to obey
commands^26. To some degree, they even seem to be able to take a
human's visual perspective^27,28,29,30. Moreover, dogs outperform
even chimpanzees in reacting appropriately to human pointing gestures
^31,32,33,34,35,36, and attend to the referential nature of the
human's gaze during social interactions^17,37,38, as well as to the
communicative intent of the human^17. They even take contextual
information into account rather than blindly following a pointing
gesture^39,40. For instance, they understand that a human does not
intend to communicate something to them when that person looks at
their watch and thereby inadvertently points towards a certain
location^17.
However, when it comes to dogs' capacity for ascribing goals, the
evidence is mixed. At first glance, some evidence speaks in favour of
such a capacity. Dogs expect agents to keep acting towards a certain
goal even if that requires a change of action^41. Also, dogs appear
to recognize the target of a human's search and show informative
motives to help find a hidden object^42. Furthermore, dogs consider
an agent's goal when they rationally imitate the agent's actions^43,
44. For example, when dogs observed another dog that used his/her paw
to pull a rod, because his/her mouth was occupied holding a ball,
they used their mouth to pull the rod (rational action). In contrast,
when they observed that the dog used his/her paw to pull the rod for
no visible reason, they imitated this inefficient action. However,
upon closer examination, dogs' performance in these tasks can be
explained by low-level, submentalizing explanations (domain-general
cognitive processes that may appear like true mentalizing but turn
out not to be upon closer inspection)^45,46. Dogs seem to have
performed the rational action in the first condition only because
they were distracted by the presence of a ball and simply missed the
presented inefficient action^47. Moreover, dogs show difficulties in
recognizing humans' implicit goals. They only help if the human
explicitly communicates her goals^36,42, or if the goal is attractive
to them^48.
Thus, while dogs appear to understand humans' communicative
intentions, their concept of human goals appears to be based much
more on trial-and-error learning. Accordingly, it may seem unlikely
that dogs have a grasp of human intentions^36,49,50^. However,
intentions have different guises. We commonly distinguish between
prior intentions (directed at the future and related to planning) and
intentions-in-action (directed at actions in the here and now)^2,51.
Accordingly, it is possible that their notion of human intentions is
not all-or-nothing, but rather comprises (only) some aspects of
understanding, presumably those that have been of direct importance
to them. Prior intentions are future-directed intentions that commit
the agent to an action, such as: "I will walk the dog tomorrow". It
is sometimes doubted, however, that non-human animals can even hold
prior intentions themselves, let alone ascribe them to other agents^2
,52. However, what is more important in interactions is to make sense
of intentions-in-action. Intentions-in-action are present-directed
intentions ("I'm walking the dog now") that underlie the voluntary
guidance of action. Observing actions enables an observer to
interpret actions as intentional ("she lay down in the grass
willingly") and distinguish it from unintentional behaviour ("she
tripped over a root"). It appears much more likely that dogs
recognize this basic form of intention. But do they really?
A very useful non-verbal approach to test for such a capacity is the
so-called "Unwilling vs. Unable" paradigm. This approach refrains
from imitations. Instead, it examines whether subjects react
differently towards a human agent who either intentionally (being
unwilling) or unintentionally (being unable) withheld rewards from
them. Using this paradigm, the capacity to distinguish intentional
from unintentional behaviour has been found not only in human infants
^12,20 but also in chimpanzees^18, African grey parrots^21, capuchins
^22, Tonkean macaques^19 and horses^23. Some of these species lost
interest in the unwilling-condition earlier than in the
unable-condition. Other species were found to differentiate in their
begging or aggressive behaviour, or in their vocalizations (for a
detailed overview of measured behavioural reactions see
Supplementary Material). From an evolutionary point of view, it is
interesting that even undomesticated species appear to recognize
intention-in-action of humans. It suggests that such a capacity is
present for interactions with other individuals and can then be
generalized flexibly to interaction with humans. However, it is also
possible that ontogeny plays a role here, i.e., that these tested
captive animals had the chance to learn this skill in their
interactions with humans. For dogs, we expect that there is both, a
potential selection pressure during domestication to discriminate
human intentions, but also the extensive possibility to learn this
during ontogeny.
To explore dogs' ability to distinguish intentional from
unintentional actions, the current study adapted the "Unwilling vs.
Unable" paradigm to make it suitable for dogs: The dogs (N = 51) were
separated from the experimenter by a transparent partition wall
(Fig. 1). The experimenter administered rewards to the dog through a
gap in the partition. In the unwilling-condition, the experimenter
suddenly withdrew the reward from the dog with an intentional
movement and placed it in front of herself. In the unable-clumsy
condition, the experimenter pretended to try to administer the
reward, but the reward "accidentally" fell out of her hand before she
could pass it through the gap. Similarly, in the unable-blocked
condition, she tried to administer the reward but was unable to pass
it through the gap because it was blocked. In all three conditions,
the experimenter left the rewards on the floor in front of her (on
her side of the partition) after failing to administer them. The dogs
received all three conditions in a counterbalanced order (see
Supplementary Material for an overview of orders). Thus, all three
conditions are similar in that a reward is brought near the dog, but
then is never passed through the gap. They are only different in
whether this action was performed in an intentional manner or in an
unintentional manner, because some circumstance hindered the agent to
perform the action. If dogs are indeed able to ascribe
intention-in-action to humans, we would expect them to show different
reactions in the unwilling-condition compared to the two
unable-conditions. As our primary measure, we looked at dogs' waiting
behaviour: How long do the dogs wait before they go around the
partition and approach the reward? We predicted that if dogs are able
to identify human intentional action, they should wait longer to
approach the reward in the unwilling-condition than in the two
unable-conditions. The logic behind this was the following: When the
experimenter intentionally withholds the reward, the dogs should
hesitate to approach it (because they predict they will not receive
it). In contrast, when she withholds it unintentionally, it is safe
to approach the reward right away (because the dogs are actually
supposed to have it). In addition to waiting behaviour, we
exploratively looked at the dogs' other behavioural reactions to the
(un)intentional withholding of rewards.
If dogs understand humans' intention-in-action, they may react
differentially depending on whether the experimenter intentionally or
unintentionally withheld a reward and, hence, dogs will show certain
reactions more in one context than another. Behavioural reactions to
unintentional and intentional actions differed substantially between
species in previous implementations of this paradigm. For instance,
parrots opened their beak^21 or infants reached for the object^12.
For this reason, we looked at a variety of reactions.
Figure 1
figure1
Experimental set-up with opened gap.
Full size image
Results
Analysis of waiting
Dogs waited longer to approach the rewards when the experimenter had
withheld them intentionally than when she did so unintentionally.
They also waited longer in the unable-clumsy condition than in the
unable-blocked condition. Fitting a Generalized Linear Mixed Model
(see Fig. 2), we looked at the effect of condition on dogs' waiting
behaviour. Waiting behaviour was operationalized by the relative
latency of going around the partition: What proportion of his/her
overall waiting time did the dog wait in each condition (see Method
for a more detailed description). To account for repeated measures,
we included random intercepts for each dog. We found an effect for
condition (kh^2 = 43.909, df = 2, p < 0.001, R^2 = 0.609). Relative
latencies were higher in the unwilling-condition than in the
unable-clumsy condition (b +- SE = - 0.486 +- 0.116, z = - 4.176, p
< 0.001) and in the unable-blocked condition (b +- SE =
- 0.847 +- 0.121, z = - 7.022, p < 0.001). On average, a dog waited
43% of his/her overall waiting time in the unwilling-condition and
only 32% in the unable-clumsy and 25% in the unable-blocked
condition. We compared both unable-conditions via Tukey post hoc
comparisons; relative latencies were higher in the clumsy than in the
blocked condition (b +- SE = - 0.360 +- 0.123, z = - 2.933, p = 0.010,
p-value adjusted for multiple comparisons). Adding the order of
conditions, the interaction of condition and order, or dogs' age to
the full model did not improve the fit of the model (all kh^2
s <= 13.241, all ps >= 0.584). We also conducted separate Spearman rank
correlations for each condition to test for a relation between
latency and trial order. These revealed no such correlation for the
unwilling or clumsy condition (all |r[s]|s <= 0.131, all ps >= 0.356).
Only in the blocked condition, dogs tended to wait less if this
condition was administered last (r[s] = - 0.277, p = 0.049). To
account for the fact that some dogs did not leave their basic
position, we also fitted a Cox Mixed Effects Model. This yielded
similar results as the Generalized Linear Mixed Model. We report
these results in the Supplementary Information.
Figure 2
figure2
Relative latencies of going around the partition. Boxplots depict 25^
th and 75^th percentiles and circles depict outliers. The fitted
model is depicted in red. Error bars of the model show the 95%
confidence interval.
Full size image
Other behavioural reactions
This is the first time this paradigm has been adapted for dogs. For
this reason, we exploratively looked at dogs' behavioural reactions
to the experimenter withholding the reward. We identified two
reoccurring behaviours that occurred in frequencies that deviated
between conditions: sitting or lying down and ceasing tail movement.
Both behavioural reactions occurred mostly in the unwilling-condition
and considerably less often in the unable-conditions (see Fig. 3).
Altogether, we observed 17 occurrences of sitting or lying down among
13 dogs (three dogs showed the behaviours in more than one condition,
see also Fig. 3). Of the overall occurrences, 65% (n = 11) were
observed in the unwilling-condition, 12% (n = 2) in the unable-clumsy
condition, and 24% (n = 4) in the unable-blocked condition. Two dogs
did not sit down in the unwilling-condition but only in the clumsy or
the blocked condition. We found a similar pattern for tail movement:
Overall, ceasing tail movement occurred 18 times among 15 dogs. Of
these 18 occurrences, 78% (n = 14) were observed in the
unwilling-condition, 17% (n = 3) in the unable-clumsy condition, and
6% (n = 1) in the unable-blocked condition. One dog ceased tail
movement only in the clumsy condition.
Figure 3
figure3
Relative frequencies of behavioural reactions. (a) depicts how often
dogs sat/lay down relative to the number of overall occurrences of
sitting and lying down. Eight dogs sat/lay down only in the unwilling
condition, three dogs in the unwilling condition and at least one
unable condition, and two dogs did not sit down in the
unwilling-condition but only in the clumsy or the blocked condition.
(b) Depicts the equivalent for ceasing tail movement. Eleven dogs
ceased moving their tails only in the unwilling condition, three in
the unwilling condition and at least one unable condition, and one
dog ceased tail movement only in the clumsy condition.
Full size image
Discussion
Dogs in our study clearly behaved differently depending on whether
the actions of a human experimenter were intentional or
unintentional. They waited significantly longer before approaching a
reward that the experimenter had withheld intentionally than a reward
that had not been administered due to human clumsiness or a physical
obstacle. Thus, dogs were able to distinguish between the
experimenter's intentional and unintentional actions. This suggests
that dogs may indeed be able to identify the experimenter's
intention-in-action.
Likewise, we found a difference between intentional and unintentional
human action in dogs' other behavioural reactions. The dogs that sat
or lay down mainly did so in the unwilling-condition. Sitting and
lying down are interpreted as so-called calming signals^53 that are
employed by dogs to appease their interaction partners. Possibly,
some dogs interpreted the intentional but not the unintentional
withholding as menacing or simply as confusing. While dogs might be
used to their owners withholding food from them, some might have been
irritated that a stranger, who readily fed them before, suddenly
withdrew the reward. To defuse the situation, they might have
employed sitting and lying down to appease the experimenter. Another
possibility is that the withholding of the reward had an activating
effect and the dogs thought that some form of learned action might
convince the unwilling experimenter to supply the reward. Hence, as a
best guess, they tried the commonly rewarded behaviours of sitting or
lying down as they have a positive emotional predisposition which
makes them more persistent and aware of signals for rewards^54.
Similarly, in other studies dogs sat down when they could not
approach forbidden food as a human was watching them^24 or when the
experimenter communicated that she expected the dog to perform a
certain behaviour (e.g., to open a door or to look for something) but
did not provide sufficiently intelligible cues what action she
expected^39,55.
In a similar manner, the dogs that ceased to move their tail mainly
did so in the unwilling-condition. Ceasing and slowing down tail
movement has been interpreted as signals for attentiveness, and
attempting to make sense of confusing situations^56,57,58. With
regard to our study, it might have confused the dogs that the
experimenter suddenly started to withhold the reward intentionally.
This interrupted the established pattern that the experimenter gives
one reward after the other. In contrast, when she tried to administer
the reward but failed, this did not interrupt this pattern and
accordingly gave no reason for confusion. Thus, all three measures
strongly suggest that dogs distinguished in their reactions between
the experimenter's intentional and unintentional actions. This
concurs with findings of previous studies on other species that also
found subjects to distinguish in their behavioural reactions to
intentional and unintentional withholding of rewards^12,18,19,20,21,
22,23. Following interpretations of these findings in other species,
this indicates that dogs can indeed recognize human
intention-in-action.
Dogs' behaviour in the two unable conditions may even suggest that
they form different expectations regarding an actor's persistence
depending on the circumstances of her failed actions. In the case of
accidents, an actor may be regarded as more likely to persevere than
in the case of physical constraints blocking her success. Such
differential expectations would explain why dogs tended to wait
longer in the clumsy condition, but approached earlier in the blocked
condition. However, this is a fairly speculative, post-hoc
explanation and further research is needed to evaluate whether beyond
distinguishing intentional from intentional actions, dogs make
differential action predictions based on the circumstances that
prevented an actor from completing her goal.
The capacity to recognize human intentional action would have been of
immense value for dogs' common history with humans. Still, our
findings that they might actually have this capacity do come as an
interesting surprise as a genuine understanding of intentions is
generally met with a great deal of scepticism^36,59. In line with
this scepticism, interpreting dogs' capacity to discriminate between
intentional and unintentional action as a genuine understanding of
intentions should be qualified by several caveats. The following part
will address possible alternative explanations.
One caveat relates to special living conditions of dogs in the human
environment. This is a substantial difference between species like
apes, monkeys and parrots^18,19,21,22 on the one side and dogs on the
other. Dogs do not only have ample interactions with humans, but they
are actively trained, also, with regards to accessing food.
Accordingly, it is possible that during these interactions, dogs
learn to read human behaviour in that they associate certain forms of
movement or facial expressions with the appropriate reaction of
approaching (or not approaching) an object^60. Such associative
behaviour rules do not allow dogs to take an intentional stance but
only to rely on associations between certain cues and reactions^36.
For example, dogs might have learned that if a reward is not
administered immediately, it might be administered later if they sit
or lie down. Similarly, they might have learned that if a food is
withdrawn, they will not receive it if they approach it. Note,
however, that while it is true that dogs, in contrast to other
species, experience ample of interactions with humans this is also
true for infants and to a lesser extent for horses. Thus, increased
interactions with humans might lead to a better discrimination
between intentional and non-intentional behaviour, be it based on a
genuine understanding of intentions or on associative learning of a
combination of behavioural cues.
It is possible that dogs' reactions in this study reflect some kind
of socio-cognitive capacity, but not an understanding of
intention-in-action. There are certain behavioural cues that in
combination with these capacities might have triggered dogs'
reactions: The withholding of the reward was accompanied by different
vocalizations that commonly signal intentional and accidental
behaviour. The experimenter's movements were held as identical as
possible. Yet, as the experimenter was not blinded, we cannot exclude
that she unconsciously provided behavioural cues. However, dogs can
recognize human emotion and are good at distinguishing positive from
negative emotions^61,62. Possibly, the unwilling-condition provided
more cues for negative emotions than the unable-conditions which
induced dogs' more hesitating reaction. Also, dogs might have
perceived the slightly more negative intonation in the
unwilling-condition as indicating a command and therefore waited
longer. Alternatively, the experimenter's behaviour might have
provided cues regarding the accessibility of the reward. Withholding
the rewards in the unwilling-condition might have signalled some form
of possession. This might have discouraged dogs to approach the
reward.
Moreover, dogs' appropriate reactions might only reflect some form of
submentalizing. For instance, dogs were rather unfamiliar with the
experimenter's behaviour and the setting. Possibly, dogs were
irritated or surprised by the experimenter's inconsistent actions in
the unwilling-condition (first giving then withdrawing the reward)
which was then reflected in a more hesitating reaction. This could
account for the difference in dogs' reactions between the unwilling
and unable-clumsy. Yet, it cannot account for the differences between
the unwilling and unable-blocked condition, as movements were
identical in these conditions.
Accordingly, there are caveats concerning interpreting our findings
as recognizing intentions-in-action. Note, however, that we chose
rather non-ostensive vocalizations that are typical communicative
signals of intention-in-action. Also, there was more similarity in
the experimenter's movements between the unwilling and unable-blocked
condition than between the unable-blocked and unable-clumsy
condition. Still, dogs waited longer in both unable-conditions. Thus,
the movements alone cannot account for dogs' distinguishing
reactions. Moreover, the results yield a rather large effect of
condition. If our findings reflected only formed (or not formed)
associations, variability among dogs should have been much higher
mirroring different levels of exposure to human interaction.
Nevertheless, future research needs to address these alternative
explanations by systematically excluding that dogs can rely on such
strategies. Such research should look at the explicit role of vocal
exclamations in dogs' reactions. To what extent do dogs use these
cues for recognizing intention-in-action or something else? Also,
future research should include dogs that have not had much contact
with humans to control for experience with human behaviour^63.
Furthermore, it would be interesting to adapt this design to wolves.
Assuming that dogs do understand human intentional action, it would
be of high interest whether this capacity developed during
domestication or whether it was a capacity that was already present
in wolves and only had to be generalized to humans. Considering that
other non-domesticated species show similar distinguishing reactions^
18,19,21,22, this seems quite possible. This would potentially
explain why dogs can make sense of some but not all aspects of human
intentions.
In conclusion, the present findings suggest that dogs recognize the
intentionality of human action in their spontaneous behaviour. Future
research needs to address whether dogs' distinguishing reaction
really reflect a capacity to read human intentions or only some form
of behaviour reading based on learned associations. Nevertheless, our
findings provide important initial evidence that dogs may have at
least one aspect of Theory of Mind: The capacity to recognize
intention-in-action.
Method
Ethical statement
We only tested pet dogs. All owners had given their consent prior to
testing. Research was non-invasive and dogs were deprived of neither
food nor water. The study was ethically approved by the Animal
Welfare Body of the University of Gottingen (consultation no.
E6-19). All methods were in accordance with relevant guidelines and
adhered to the legal requirements of Germany. Informed consent was
obtained for publication of identifying information/images (Figs. 1,
4, 5, Video S1) in an online open-access publication.
Subjects
We analysed data of 51 dogs (27 female and 24 male) of various breeds
and ages (range: 1-15 years, M = 5.80, SD = 3.05; see Supplementary
for an overview of age, sex, and breed). We only tested dogs who had
not received special training, as for example police dogs or
registered rescue dogs. Five other dogs were tested but had to be
excluded from analyses because they did not meet the inclusion
criteria (see below). Sample size was estimated a priori via G*Power
3.1.9.2 assuming e^2 = 0.2 (based on piloting results) and 1 - ss =
0.8. Dogs were recruited from the Dog Studies Database of the Max
Planck Institute for the Science of Human History.
Experimental set-up
Dogs were tested in a quiet room by two female experimenters (E1 and
E2). The owners were not present. The apparatus (see Fig. 4)
consisted of two partition walls (each wall: 1.45 m wide x 1.15 m
high). Each wall consisted of a wooden frame holding a sheet of
transparent plastic. One side of the frame was open. The two walls
were positioned next to each other in such a way that the two open
sides faced each other. They could be pushed together completely or
pulled apart, to form a 15 cm-wide gap. This gap allowed the
experimenter to pass rewards through the partition. It always
remained open, except in the unable-blocked condition. Dogs were
always placed on the opposite side of the apparatus of E1. In front
of E1 was a ramp (0.35 m long x 0.65 cm wide x 0.20 m high). This
ramp ensured that all rewards (whether intentionally placed or
accidentally dropped) would end up approximately in the same
location.
Figure 4
figure4
Experimental set-up.
Full size image
Procedure
We allowed the dog to explore the room freely for a few minutes to
familiarize him/herself with the setting. Dogs that stayed near the
exit were encouraged by E1 to move around via positive verbal
reinforcement.
Familiarization
The familiarization phase consisted of two steps. First, we showed
the dogs that they could go around the partition. E1 directed the dog
to the basic feeding position facing the partition wall. E1 herself
took place on the opposite side of the partition. To test whether the
dog understood that they could go around the separation wall on
either side, E1 encouraged the dog verbally to go around the
partition and approach her. E1 stayed seated during this process.
Only when dogs failed to go around the partition, E1 went halfway
around the wall to demonstrate this possibility. This was repeated
until the dog successfully went around the wall. Dogs who did not
reach this criterion within 1.5 min were excluded (n = 2).
Afterwards, E1 redirected the dog back to the basic feeding position.
In the second step, the dogs were familiarized with the
administration of rewards through the gap in the partition. E1
administered rewards through the gap. Dogs were required to take five
rewards in a row without leaving their basic position. We excluded
dogs that did not reach this criterion (e.g., because of distraction,
n = 3). Only then was the test phase started.
Test
Each dog received one test trial per condition in a balanced order.
In between test trials, we administered filler trials.
Test trials
The rationale of each condition was as follows: E1 tried to give a
reward to the dog but, for either intentional or unintentional
reasons, ended up not doing so. Instead, either she placed the reward
immediately in front of herself on the floor or the reward fell out
of her hand. The movement of (not) giving the reward was repeated up
to five times. These movements were identical in terms of pace
(roughly 23 s) throughout the conditions. Then, E1 turned away and
focused on her coding sheet for five seconds. When the dog went
around the partition before all five rewards were placed on the
floor, E1 terminated the trial. Each condition's presentation took
roughly 28 s, unless dogs left the basic position earlier.
Unwilling-condition
The gap between the two walls was open. E1 moved a reward towards the
gap but intentionally pulled the reward away in a fast motion. While
pulling it away, she exclaimed "ha-ha!". These utterances were added
as non-ostensive but common vocal communicative signals that are used
to underline an attitude towards actions. E1 then placed the reward
immediately in front of herself, on her side of the partition.
Unable-clumsy condition
This condition was similar to the unwilling-condition, but with one
exception: Instead of intentionally pulling the reward away, E1
"accidently" dropped the reward and exclaimed "oops!". The rewards
were dropped onto the ramp. This way, they rolled to the same
location where E1 put them in the other conditions.
Unable-blocked condition
In this condition, E2 entered the room and closed the gap between the
partition walls by pushing both walls together. E1 then moved the
reward towards the wall, but the partition made it impossible to
administer the reward. When hindered, she exclaimed "oh!" and put the
reward in front of her. The speed and nature of this movement was
similar to the unwilling-condition. Note that some dogs reacted to
the closing of the gaps. Dogs however immediately reoriented their
attention, when the first reward was held up. Twelve dogs went around
the walls as a reaction to closing the partition walls. In these
cases, we repeated the familiarization and closed the gap a second
time.
Filler trials
In the filler trials, E1 gave rewards to the dog through the gap.
Just as in the familiarization phase, this was done until the dog had
eaten five rewards in succession without leaving the basic position.
The reason behind this was to maintain "E1 gives rewards through the
gap" as the default event.
Coding
All test sessions were recorded. Videos were then used for coding. We
used BORIS^64 to code the dogs' behaviour. To analyse dogs' waiting
behaviour, we coded the latencies of going around the partition.
Absolute latencies were coded as the time interval t[0] - t[1]:
t[0]: E1's hand leaves the bag of rewards (retrieving the reward).
t[1]: Dog's head aligns with partition wall (see Fig. 5 for an
example).
Figure 5
figure5
(t[0]) shows an example of a starting point of a time interval: E1
retrieves the reward. (t[1]) shows an example of an end point of a
time interval: dog's head aligns with partition.
Full size image
To account for inter-individual differences, we computed the dogs'
relative latencies: For each dog, we divided his or her latency in
one condition by the sum of his or her latencies in all three
conditions.
Moreover, we coded dogs' behavioural reactions that occurred in the
course of this time interval (t[0] - t[1]; for a full ethogram see
Supplementary Material). Latencies and behavioural reactions were
coded by two second coders who were blind to hypotheses. They coded
20% of the subjects. Interrater agreement for both measures was
almost perfect (latencies: (r[s] = 0.975), behavioural reactions: k =
0.982).
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Download references
Acknowledgements
We thank Josepha Erlacher and Katharina Schulte for help with data
collection, Leonie Baumann and Franziska Roth for reliability coding,
and Katrin Schumann for acquisition of the participating dogs and
organization of data collection. We also thank Russel Barlow for his
very helpful feedback on the manuscript.
Funding
Open Access funding enabled and organized by Projekt DEAL. JK
received a grant from the "Creativity and Studies"-competition of the
University of Gottingen for this project. This grant is funded by the
AKB-foundation. BS received funding from Evangelisches Studienwerk
Villigst and Studienstiftung des Deutschen Volkes and Deutsche
Forschungsgemeinschaft (DFG, German Research Foundation) - Project
number 254142454 / GRK 2070.
Author information
Author notes
1. These authors contributed equally: Britta Schunemann and Judith
Keller.
Affiliations
1. Department of Developmental Psychology, University of Gottingen,
Waldweg 26, 37073, Gottingen, Germany
Britta Schunemann, Judith Keller, Hannes Rakoczy & Tanya Behne
2. Department of Biology, University of Hamburg,
Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
Judith Keller
3. Department of Linguistic and Cultural Evolution, Max Planck
Institute for the Science of Human History, Kahlaische Strasse
10, 07745, Jena, Germany
Juliane Brauer
4. Department for General Psychology and Cognitive Neuroscience,
Friedrich Schiller University of Jena, Am Steiger 3, 07743, Jena,
Germany
Juliane Brauer
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Contributions
B.S. and J.K. initiated the research. All authors contributed to the
study conception and design. J.K. and B.S. prepared the material.
J.K. collected the data with support from J.B.. B.S. and J.K.
analysed the data. The first draft of the manuscript was written by
B.S. with support from J.K.. All authors commented provided feedback
on the manuscript.
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Schunemann, B., Keller, J., Rakoczy, H. et al. Dogs distinguish human
intentional and unintentional action. Sci Rep 11, 14967 (2021).
https://doi.org/10.1038/s41598-021-94374-3
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* Accepted: 09 July 2021
* Published: 01 September 2021
* DOI: https://doi.org/10.1038/s41598-021-94374-3
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