The Cognitive Abilities Underpinning Search for
Hidden Objects in the Domestic Dog (Canis familiaris)
Rebecca Ashton ([email protected]) and Carlo De Lillo ([email protected])
Henry Wellcome Building, University of Leicester
Studying Cognition of Dogs with
Object Search
On the basis of the results of recent research in comparative
cognition, it has been suggested that dogs have a level of
cognitive sophistication that parallels that of species
taxonomically much closer to humans such as chimpanzees
and other apes.
Some of this evidence has been gathered from search tasks
involving retrieving hidden objects on the basis of some cues
which could include human gestures.
The Current Study
Graph 1
Experiment 1 – Hiding Event witnessed in Pre-Reversal and Reversal
Percentage Correct Reversal
This research aims to understand which type of cues are the
most effective in guiding dogs’ search behaviour, and also the
extent to which dogs’ competence in retrieving hidden objects
relies on human gestures, as apposed to other sources of
information.
Methods
Training
19 pet dogs (Canis familiaris) trained to identify which of two containers
contained a bait. Performance to a criterion (80% correct) over a series
of trials was measured:
Graph 2
Experiment 2 – No Hiding Event in Pre-Reversal
Percentage Correct Reversal
Reward Contingency
Mediational Learning Paradigm
Measures Learning Strategies
The Mediational Learning Paradigm (Rumbaugh & Pate, 1984) is a
variation of a discrimination reversal task which allowed experimenters
to assess whether different primate species learn to discriminate objects
on the basis of the gradual development of associations or by using
higher level mediational strategies which would support one-trial
learning (e.g. De Lillo & Visalberghi, 1994; Rambaugh, 1971).
Locations labelled A to D. Positive
symbol signifies location of reward. 4
locations out of a possible 12 were
selected for problems to create the
reward contingencies. Each dog
completed 3 problems.
Reversals
A-B+
Graph 3
Experiment 3 – No Hiding Event Witnessed in either Pre-Reversal or Reversal
Percentage Correct Reversal
Learning by Association
Early theories of classical and instrumental learning dictate that simple
connections between pairs of responses or objects in the environment
allow animal learning based on repetition, positive reward and negative
inhibition (Hull, 1943; Spence, 1937).
A More Flexible Search Strategy
A-C+
B+D-
Levine (1959, 1970) proposed that animals may use a 'win stay-lose shift',
strategy which would support efficient search of two locations: the
animal will continue searching in a location until there is no reward, then
it will switch search location.
Results
Reversal Contingencies
Understanding Humans Through
Gestures
Dogs are able to use human social cues effectively to look for hidden
objects. This ability has been attributed to dogs’ co-evolution with
humans (Hare & Tomasello, 2005), and could support success in
variants of the object permanence task (Piaget, 1953) in which the dog
must search for an object visibly hidden by humans in one of multiple
hiding locations.
When such hiding cues conveyed by human gestures are available,
dogs perform very well in object search tasks (Hare et al. 1998; Miklosi
et al, 1998; Agnetta et al, 2000), suggesting that they may use social
cues as a strategy for search.
Condition AB features both locations used during training but with their reward
contingencies reversed. AC has a novel location C rewarded and paired with A,
now not rewarded. Finally, in BD the novel location D is not rewarded and is
paired with previously unrewarded location B, now rewarded.
Exposure to Human Gestures to Predict
Flexibility in Learning
Three experiments measured the extent to which dogs could
rely on the observation of a hiding event
In the first control experiment there was witnessing of the
hiding event in both training and reversal
Experiment 2 had witnessing of hiding in the reversal phase
only. A screen was lowered during the hiding event so that it
was not visible.
In Experiment 3 there was no witnessing of hiding in either
both training or reversal phases
However, it is unclear when given a choice between suggestive cues
conveyed by human gestures and associative learning based on
previous experience to predict the location of a hidden object, which
strategy the dog will use.
Associative learning theory predicts that dogs’ performance will be
reduced in the AB condition, as this reversal includes a complete
exchange of reward contingencies. Mediational use of human hiding
gestures predicts: 1) a similar performance in all reversal conditions
where dogs witness the hiding event and 2) more pre-reversal trials to
criterion performance in experiments 2 and 3, in which dogs do not
witness the hiding gesture.
Witnessing a hiding event does not completely
override associative learning
The results of the experiments 1 and 2 show that the full
reversal contigency AB had the lowest performance in
search, even when witnessing a hiding event would
have enabled the dogs to locate the bait irrespectively of
previous reward contingencies. (graphs 1 and 2).
Availability of Human Cues Affects Performance
This 'A not B' error is found in all three experiments
(experiment 1 visible hiding gesture to experiment 3 no
visible hiding gesture), suggesting that regardless of
information from the hiding event, dogs prefer to use
previous location-reward associations rather than visual
cues (graphs 1-3).
The Strength of Reward
In the absence of hiding gestures, the difference in the
AC (previously rewarded and novel location) and BD
reversals (previously unrewarded and novel location)
highlights the unbalanced weight of reward and non
reward from training (graph 3).
Dogs Seem to Use Both Associative Learning
and Cues Transmitted by human gestures in
Object Search
Whereas the unequal performance in the different
reversal conditions indicates that associative learning
plays a strong role in dogs search, the fact that the
performance was reduced in conditions where subjects
witnessed the hiding event during the pre-reversal
phase (see graph 4) indicates that dogs do not rely
exclusively on associative learning when retrieving a
hidden bait.
Pre-reversal Percentage Correct
Graph 4
100
References
80
60
Exp 1
Exp 2
Experiment
Exp 3
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