Does the A-not-B error in adult pet dogs indicate sensitivity to human communication?

Recent dog-infant comparisons have indicated that the experimenter's communicative signals in object hide-and-search tasks increase the probability of perseverative (A-not-B) errors in both species (Topál et al. 2009). These behaviourally similar results, however, might reflect different mechanisms in dogs and in children. Similar errors may occur if the motor response of retrieving the object during the A trials cannot be inhibited in the B trials or if the experimenter's movements and signals toward the A hiding place in the B trials ('sham-baiting') distract the dogs' attention. In order to test these hypotheses, we tested dogs similarly to Topál et al. (2009) but eliminated the motor search in the A trials and 'sham-baiting' in the B trials. We found that neither an inability to inhibit previously rewarded motor response nor insufficiencies in their working memory and/or attention skills can explain dogs' erroneous choices. Further, we replicated the finding that dogs have a strong tendency to commit the A-not-B error after ostensive-communicative hiding and demonstrated the crucial effect of socio-communicative cues as the A-not-B error diminishes when location B is ostensively enhanced. These findings further support the hypothesis that the dogs' A-not-B error may reflect a special sensitivity to human communicative cues. Such object-hiding and search tasks provide a typical case for how susceptibility to human social signals could (mis)lead domestic dogs.     

The role of attentiveness,mobility history,and separation of hiding sites on stage IV search behavior

The relationship between visual attentiveness, search behavior, and duration of independent mobility was examined for fifty-six 8- to 10-month-old infants presented with three versions of the Stage IV object permanence task. The number and spatial separation of hiding sites was manipulated to explore the role of these factors on visual attention and search performance. In a repeated measures design, perseverative search errors were less likely on both a two- and a six-location task with equally wide separation of the A and B hiding sites than on a two-location task with A and B close together, thus indicating that spatial separation of sites is a more important contributor to successful search than number of hiding sites alone. In addition, visual attentiveness was significantly associated with correct search at B in all three versions of the task. A significant developmental relationship was found between the length of time infants had been independently mobile and visual attentiveness during the hiding procedure. These findings are discussed in terms of the transition to self-produced mobility and expanding spatial experience in the second half of the first year and how visual attentiveness and search performance might improve as a function of such changes.     

Infants' search for visible objects: implications for the interpretation of early search errors

This study examined the error patterns of 9-month-old infants searching for hidden objects and objects that were visible within a container. Although errors occurred in both conditions, there were important differences between them. When the object was hidden, infants showed significant perseveration in that they searched more often at the object's previous hiding place than at a control location. When the object was visible, however, they made fewer errors and the errors they did make were as likely to be to the control location as to the previous hiding place. These results suggest that infants' errors in searching for a visible object reflect lapses of attention rather than systematic misunderstandings of objects or space and so are not incompatible with an information-processing account of early search.     

Two-Year-Olds' Object Retrieval Based on Television: Testing a Perceptual Account

Two-year-olds frequently fail to use information provided by video to find objects hidden in an adjacent room. Schmitt and Anderson (2002) hypothesized that they fail to map the 2-dimensional (2D) video image onto the 3D layout of the search space. Two experiments tested whether 2-year-olds can successfully use information from video when the search space is 2D or when the information is provided verbally (by telling the child where the toy is hidden). In both experiments, children performed poorly in the video conditions but performed well in direct live experience comparison conditions, contradicting Schmitt and Anderson's hypothesis. Performance was above chance on the first trial in the video conditions, suggesting that 2-year-olds do have a memory of the hiding location, albeit one that is easily disrupted by perseverative errors on subsequent trials. Overall, the results are most consistent with the hypothesis that very young children give priority to direct experience over mediated information.     

Duration of cats' (Felis catus) working memory for disappearing objects

This study explored the duration of cats' working memory for hidden objects. Twenty-four cats were equally divided into four groups, which differed according to the type of visual cues displayed on and/or around the hiding boxes. During eight sessions, the four groups of cats were trained to locate a desirable object hidden behind one of the four boxes placed in front of them. Then, the cats were tested with retention intervals of 0, 10, 30 and 60 s. Results revealed no significant differences between the groups during training or testing. In testing, the cats' accuracy to locate the hidden object rapidly declined between 0 and 30 s but remained higher than chance with delays of up to 60 s. The analysis of errors also indicated that the cats searched as a function of the proximity of the target box and were not subjected to intertrial proactive interference. This experiment reveals that the duration of cats' working memory for disappearing objects is limited and the visual cues displayed on and/or around the boxes do not help the cats to memorize a hiding position. In discussion, we explore why the duration of cats' working memory for disappearing objects rapidly declined and compare these finding with those from domestic dogs. The irrelevance of visual cues displayed on and around the hiding boxes on cats' retention capacity is also discussed.     

One-year-olds comprehend the communicative intentions behind gestures in a hiding game

This study explored infants' ability to infer communicative intent as expressed in non-linguistic gestures. Sixty children aged 14, 18 and 24 months participated. In the context of a hiding game, an adult indicated for the child the location of a hidden toy by giving a communicative cue: either pointing or ostensive gazing toward the container containing the toy. To succeed in this task children had to do more than just follow the point or gaze to the target container. They also had to infer that the adult's behaviour was relevant to the situation at hand - she wanted to inform them that the toy was inside the container toward which she gestured. Children at all three ages successfully used both types of cues. We conclude that infants as young as 14 months of age can, in some situations, interpret an adult behaviour as a relevant communicative act done for them.     

Unifying representations and responses: perseverative biases arise from a single behavioral system

Abstract— A dominant account of perseverative errors in early development contends that such errors reflect a failure to inhibit a prepotent response. This study investigated whether perseveration might also arise from a failure to inhibit a prepotent representation. Children watched as a toy was hidden at an A location, waited during a delay, and then watched the experimenter find the toy. After six observation-only A trials, the toy was hidden at a B location, and children were allowed to search for the toy. Two- and 4-year-olds' responses on the B trials were significantly biased toward A even though they had never overtly responded to this location. Thus, perseverative biases in early development can arise as a result of prepotent representations, demonstrating that the prepotent-response account is incomplete. We discuss three alternative interpretations of these results, including the possibility that representational and response-based biases reflect the operation of a single, integrated behavioral system.     

Do dogs (Canis familiaris) understand invisible displacement?

Domestic dogs (Canis familiaris) perform above chance on invisible displacement tasks despite showing few other signs of possessing the necessary representational abilities. Four experiments investigated how dogs find an object that has been hidden in 1 of 3 opaque boxes. Dogs passed the task under a variety of control conditions, but only if the device used to displace the object ended up adjacent to the target box after the displacement. These results suggest that the search behavior of dogs was guided by simple associative rules rather than mental representation of the object's past trajectory. In contrast, Experiment 5 found that on the same task, 18- and 24-month-old children showed no disparity between trials in which the displacement device was adjacent or nonadjacent to the target box.     

Gravity does rule for falling events

Hood (1995) reported a vertical invisible displacement task where the goal was to find a ball that was dropped down one of three chimneys connected to three hiding boxes below by opaque tubes. Preschool children exhibited perseverative search at the box directly below the chimney where the ball was dropped even though the tubes were always visible and the children were given numerous trials and feedback. This behavior was interpreted as a naive theory of gravity. The current study set out to test the naive gravity theory hypothesis by reversing the motion of the event on a television. On half of the trials the object appeared to fall up the tube into one of the boxes which were now on the top of the apparatus. There were significantly more errors for ‘down’ trials as compared to ‘up’ trials which supports the hypothesis that children are biased to infer that falling objects travel in a straight line whereas anti-gravity events do not conform to this naive theory.     

The role of target distinctiveness in infant perseverative reaching

From a dynamic systems perspective, perseverative errors in infancy arise from the interaction of the perceptual cues with the memory of previous actions. To evaluate this account, we tested 9-month-old infants in a task in which they reached for two targets. Experimenters repeatedly cued the first target, which always matched the background (A), and then cued the second target, which varied in its distinctiveness (B). We predicted that a sufficiently distinctive B target would lessen perseverative responding. Results showed that infants perseverated when reaching for two identical targets, but that they made nonperseverative responses when reaching in the presence of a highly distinctive B target. Reach direction on each trial was jointly determined by the distinctiveness of the target, the immediately preceding perceptual events, and the history of reaches in the task.     

The effects of cue reliability on infants' manual search.

Nine-month-old babies were presented a manual search problem in which toys were hidden in one of two containers, and then the containers were transposed. Over a series of training trials either two, one, or no cues were perfectly correlated with the location of the toy. The infants' first searches became more accurate over training trials in conditions with consistent container and/or position cues. In the final training trial block search performance was best with two cues, intermediate with one cue, and least accurate in the no-cue condition. In a subsequent reversal procedure, in which the toy was placed in the previously unused hiding place, the number of correct first searches also differed according to the nature of cues available across hidings. The implications for learning the concept of object permanence are discussed.     

Pointing gestures modulate domestic dogs’ search behavior for hidden objects in a spatial rotation problem

In the spatial domain, domestic dogs are highly inclined to search at the last location where they saw an object disappear and cannot infer that a hidden object has moved imperceptibly from one location to another. In the current study, we examined whether exposure to human social cues modulates dogs’ search behavior for hidden objects. In Experiment 1, twenty dogs were first trained to find an object they saw disappear inside a stationary container in the presence (social group) or absence (non-social group) of pointing gestures. In tests, the containers were rotated 180° around a central axis. The dogs in the non-social group systematically searched at the initial (now incorrect) hiding location, whereas the dogs in the social group chose correctly significantly above chance. In Experiment 2, we tested whether pre-exposure to human pointing has an impact on dogs’ use of gestures. No gestures were given during training and both the social and non-social conditions were administered to each of the ten dogs. In contrast to Experiment 1, the performance of dogs in the social condition dropped significantly and varied substantially from one dog to another. Overall, this study suggests that dogs’ tendency to use human signals is so strong that it even outweighs their spatial bias to search where they saw an object disappear; however, this penchant to use human gestures appears to be dependent on the degree of familiarity of the dog with these signals.     

Do chimpanzees (Pan troglodytes) and 2-year-old children (Homo sapiens) understand double invisible displacement?

Chimpanzees (Pan troglodytes) and young children (Homo sapiens) have difficulty with double invisible displacements in which an object is hidden in two nonadjacent boxes in a linear array. Experiment 1 eliminated the possibility that chimpanzees' previous poor performance was due to the hiding direction of the displacement device. As in Call (2001), subjects failed double nonadjacent displacements, showing a tendency to select adjacent boxes. In Experiments 2 and 3, chimpanzees and 24-month-old children were tested on a new adaptation of the task in which four hiding boxes were presented in a diamond-shaped array on a vertical plane. Both species performed above chance on double invisible displacements using this format, suggesting that previous poor performance was due to a response bias or inhibition problem rather than a fundamental limitation in representational capacity.     

Object disappearance and error in Piaget's Stage IV task

Piaget attributes perseverative error in infant manual search to the failure of the infant to conceive of objects as permanent entities which retain their identity when hidden at successive locations A and B. An experiment was performed to test this explanation in which search was compared under three conditions: when the object was hidden at A and B, when the object was covered but visible at A and B, and when the object was visible and uncovered at A and B. Errors occurred under all three conditions taking the form of a conflict in which infants searched persistently either at A or at B. The conflict was at a maximum when the object was hidden, but was evident even when the object was visible but covered. It is suggested that errors may reflect lack of coordination between egocentric and visual frames of reference in relation to which the object is located.     

Two‐year‐old children but not domestic dogs understand communicative intentions without language,gestures, or gaze

Infants can see someone pointing to one of two buckets and infer that the toy they are seeking is hidden inside. Great apes do not succeed in this task, but, surprisingly, domestic dogs do. However, whether children and dogs understand these communicative acts in the same way is not yet known. To test this possibility, an experimenter did not point, look, or extend any part of her body towards either bucket, but instead lifted and shook one via a centrally pulled rope. She did this either intentionally or accidentally, and did or did not address her act to the subject using ostensive cues. Young 2‐year‐old children but not dogs understood the experimenter's act in intentional conditions. While ostensive pulling of the rope made no difference to children's success, it actually hindered dogs' performance. We conclude that while human children may be capable of inferring communicative intent from a wide variety actions, so long as these actions are performed intentionally, dogs are likely to be less flexible in this respect. Their understanding of communicative intention may be more dependent upon bodily markers of communicative intent, including gaze, orientation, extended limbs, and vocalizations. This may be because humans have come under selective pressure to develop skills for communicating with absent interlocutors – where bodily co‐presence is not possible.     

Author Index to Volume 4

Age-appropriate modifications of the A-not-B task were used to examine 2-year-olds' search behavior. Several theories predict that A-not-B errors will increase as a function of number of A trials. However, the hierarchical competing systems model (Marcovitch &; Zelazo, 1999) predicts that although the ratio of perseverative to nonperseverative errors will increase, the likelihood of perseveration will be an inverted U-shaped function. In Experiment 1, children received 1, 6, or 11 A trials in a multistep multilocation search task. In Experiment 2, children received 3, 7, 11, or 15 A trials in a sandbox task. Results from Experiment 1 showed that the ratio of perseverative to nonperseverative errors increased with number of A trials, and results from both Experiments 1 and 2 indicated that the likelihood of perseverative errors was highest following a moderate number of A trials. These findings are consistent with the suggestion that search behavior provides an index of the development of conscious control.     

Association, inhibition, and object permanence in dogs' (Canis familiaris) spatial search

The relative role of associative processes and the use of explicit cues about object location in search behavior in dogs (Canis familiaris) was assessed by using a spatial binary discrimination reversal paradigm in which reversal conditions featured: (1) a previously rewarded location and a novel location, (2) a previously nonrewarded location and a novel location, or (3) a previously rewarded location and a previously nonrewarded location. Rule mediated learning predicts a similar performance in these different reversal conditions whereas associative learning predicts the worst performance in Condition 3. Evidence for an associative control of search emerged when no explicit cues about food location were provided (Experiment 1) but also when dogs witnessed the hiding of food in the reversal trials (Experiment 2) and when they did so in both the prereversal and the reversal trials (Experiment 3). Nevertheless, dogs performed better in the prereversal phase of Experiment 3 indicating that their search could be informed by the knowledge of the food location. Experiment 4 confirmed the results of Experiments 1 and 2, under a different arrangement of search locations. We conclude that knowledge about object location guides search behavior in dogs but it cannot override associative processes.     

A nonverbal test of knowledge attribution: a comparative study on dogs and children

The sensitivity of eleven pet dogs and eleven 2.5-year-old children to others’ past perceptual access was tested for object-specificity in a playful, nonverbal task in which a human Helper’s knowledge state regarding the whereabouts of a hidden toy and a stick (a tool necessary for getting the out-of-reach toy) was systematically manipulated. In the four experimental conditions the Helper either participated or was absent during hiding of the toy and the stick and therefore she knew the place(s) of (1) both the toy and the stick, (2) only the toy, (3) only the stick or (4) neither of them. The subjects observed the hiding processes, but they could not reach the objects, so they had to involve the Helper to retrieve the toy. The dogs were more inclined to signal the place of the toy in each condition and indicated the location of the stick only sporadically. However the children signalled both the location of the toy and that of the stick in those situations when the Helper had similar knowledge regarding the whereabouts of them (i.e. knew or ignored both of them), and in those conditions in which the Helper was ignorant of the whereabouts of only one object the children indicated the place of this object more often than that of the known one. At the same time however, both dogs and children signalled the place of the toy more frequently if the Helper had been absent during toy-hiding compared to those conditions when she had participated in the hiding. Although this behaviour appears to correspond with the Helper’s knowledge state, even the subtle distinction made by the children can be interpreted without a casual understanding of knowledge-formation in others.     

Representation and Perseveration: Influences on Young Children's Representational Insight

We carried out 3 experiments to determine what role different task demands play in 2.5-year-old children's performance on DeLoache's (1987) model-room task. The results of Experiment 1 reveal that the size of the toy to be retrieved had little bearing on performance; only the size of the spaces affected performance. Experiment 2 demonstrated that the large number of perseverative errors produced by children in these tasks was not reduced when the toy on each of the 4 test trials was changed and, thus, further suggested that characteristics of the toy had little influence on performance. Experiment 3 showed that elimination of the possibility of perseverative response through removal of the previously used hiding locations did not facilitate transfer. The results point to conceptual inflexibility or difficulty of engagement in dual representation associated with the search space as important contributors to the lack of representational insight demonstrated by 2.5-year-old children.     

Rhythmic ostensive gestures: How adults facilitate infants’ entrance into early triadic interactions

For decades, the literature on the emergence of triadic interactions considers the end of the first year of life as the time when children become able to communicate with others intentionally about a referent. Prior to that, children only relate in dyads, either with someone else or with an object. However, several researchers claim that referents are not naturally given in human communication and that they need to be established in interaction with others.In this study, we focus on earlier triadic interactions initiated by adults, when young babies still require an adult to bring the material world within their reach. In these early triadic interactions, ostensive gestures (with the object in the hand) are one of the first means of enabling the establishment of shared reference. Such gestures are easier to understand since sign (gesture) and referent (object) coincide. We conducted a longitudinal study with 6 babies filmed at 2, 3 and 4 months old in interaction with their mothers and a sounding object (a maraca). We analyzed different communicative initiatives by the adult and the child’s responses.The results show that children come to understand the adult’s communicative intention gradually through interaction. Adults include children in organized communicative “niches” based on ostensive actions, both through ostensive gestures and demonstrations of the use of the object. Consequently, the first shared understandings between adult and child take place around the object and its uses. Rhythm is a powerful tool used to structure the interaction. Eventually, adults provide space to children to actively interact with the sounding object themselves. These results highlight the importance of considering ostensive actions as a communicative tool that favors joint attention and action. They also bring some light to the interdependence between a child who actively perceives and acts, and the structured situation that the adult organizes for them.