What comes first? How selective attentional processes regulate the activation of a motor routine in a manual search task

An intriguing error has been observed in toddlers presented with a 3-location search task involving invisible displacements of an object, namely, the C-not-B task. In 3 experiments, the authors investigated the dynamics of the attentional focus process that is suspected to be involved in this task. In Experiment 1, 2.5-year-old children were tested on a new adaptation of the C-not-B task in which the opening of the experimenter's hand between cloths provided visual information about the correct localization of the toy. Children still emitted a strong response bias toward the last hiding place. In Experiment 2, 2.5-year-old children were tested on a new version of the task that was designed to investigate the role of the central location in the task. This 2nd experiment demonstrated that changing the hand's movement from A to C to B did not enable children to succeed in the task. In Experiment 3, 2.5-year-old children were tested in a situation that is analogous to the C-not-B with open hands task except for the fact that the experimenter dropped the toy under the 1st cloth in the path. Toddlers succeeded when the toy was hidden at Location A but not when it was hidden at Location B. Data indicate that attentional focus on the experimenter's hand motion is contingent on whether that stimulus is critical to performing the task. We argue that these findings provide a potential mechanism through which motor routines can be regulated in accordance with strategic intentions.     

Two‐year‐olds use adults' but not peers' points

In the current study, 24‐ to 27‐month‐old children (N = 37) used pointing gestures in a cooperative object choice task with either peer or adult partners. When indicating the location of a hidden toy, children pointed equally accurately for adult and peer partners but more often for adult partners. When choosing from one of three hiding places, children used adults’ pointing to find a hidden toy significantly more often than they used peers’. In interaction with peers, children's choice behavior was at chance level. These results suggest that toddlers ascribe informative value to adults’ but not peers’ pointing gestures, and highlight the role of children's social expectations in their communicative development.     

Differences in the memory-based searching of delayed and normally developing young children

The memory-based searching of developmentally delayed and normal 2-year-old children was compared. The results of the study confirmed the hypothesis that individual differences would be minimal in a relatively noneffortful memory task, but that substantial individual differences would occur when more cognitive effort was required. The performance of the delayed and normal children was very good and quite similar in the basic memory task, which simply involved remembering the location of a toy hidden in a distinctive, natural location in a room. Substantial individual differences were found, however, in the children's ability to draw inferences about plausible locations for a missing toy based on their memory for where it had been hidden. When they discovered that their toy was not where they remembered it had been hidden (it had been surreptitiously moved by the experimenter), a group of normal children searched for the toy in places that were nearby or otherwise related to the original location of the toy. They used their memory for where the toy had been hidden to generate plausible alternative locations to search. In contrast, delayed children, who discovered their toy to be unaccountably missing from a location, persevered in repeatedly searching that same place. Unlike the normal children, they did not try something new. An important aspect of the data reported is that they reveal an important difference-not just a delay-in the cognitive functioning of young delayed children.     

Perceptual Sensitivity and Motoric Competence in 5- and 6-Month-Old Infants

The authors explored whether 5- to 6-month-old infants were sensitive to perceptual information and how they used perception as a recognition cue to search for a hidden object. In addition, the authors categorized and examined infant grasp by developmental effectiveness to determine any impact on infant search behaviors. In a within-participants design, 20 infants were presented with a toy in 2 occluder conditions. The toy was hidden under either a thick, camouflaging cloth or a thin, semitransparent cloth. The data revealed significant effects of perceptual sensitivity, age, and motor sophistication on search tasks. The results suggest that motor competence might be a limiting factor in infants' abilities to link motoric responses to notions about an object.     

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.     

Perceptual sensitivity and motoric competence in 5- and 6-month-old infants

The authors explored whether 5- to 6-month-old infants were sensitive to perceptual information and how they used perception as a recognition cue to search for a hidden object. In addition, the authors categorized and examined infant grasp by developmental effectiveness to determine any impact on infant search behaviors. In a within-participants design, 20 infants were presented with a toy in 2 occluder conditions. The toy was hidden under either a thick, camouflaging cloth or a thin, semitransparent cloth. The data revealed significant effects of perceptual sensitivity, age, and motor sophistication on search tasks. The results suggest that motor competence might be a limiting factor in infants' abilities to link motoric responses to notions about an object.     

Television and Reality: Toddlers' Use of Visual Information from Video to Guide Behavior

Toddlers' ability to use a television display in order to guide their object retrieval and object placement was examined. In the first experiment, 2-, 2.5-, and 3-year-olds watched a toy being hidden in an adjacent room, after which they were asked to find it. In the second experiment, 2-year-olds watched a toy being placed in the adjacent room and were then asked to place the toy in the same place. Half the children in each experiment watched the event through a window and half watched the event on television. In both experiments children's performance was worse if they saw the event on television, although retrieval improved with age. In both experiments the 2-year-olds' performance in the television condition started above chance and then deteriorated over trials. These and other studies indicate that toddlers have considerable difficulty using a video image in order to guide behavior in a real setting. Three hypotheses that could account for these findings are discussed.     

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.     

The role of perseveration in children's symbolic understanding and skill

In the first few years of life, children become increasingly sensitive to the significance of a variety of symbolic artifacts. An extensive body of research has explored very young children's ability to use symbol‐based information as a guide to current reality. In one common task, for example, children watch as a miniature toy is hidden in a scale model, and are then asked to retrieve a larger version of the toy from the corresponding place in the room itself. Two‐and‐a‐half‐year‐old children perform very poorly in most versions of this task. Their most common error is to perseverate; that is, they search again at the location where the toy was last hidden. Two studies examined the degree to which 2¹/₂‐year‐olds’ high rate of perseveration and poor performance stem from problems with inhibitory control. Results showed that problems with inhibitory control contribute very little to 2¹/₂‐year‐old children's difficulty with the task. Instead, the results confirm young children's great difficulty appreciating and exploiting symbol–referent relations.     

GENERALITY AND SIDE EFFECTS OF OVERCORRECTION1

The effects and side effects of overcorrection for self-stimulatory behaviors of two children in a specialized day-care program were evaluated. For one child, a “hand” overcorrection procedure involving arm and hand exercises was introduced contingent upon inappropriate hand movements and later contingent upon inappropriate foot movements. After “hand” overcorrection was withdrawn for inappropriate foot movements, a “foot” overcorrection procedure involving foot and leg exercises was introduced contingent upon inappropriate foot movements. For a second child, the “hand” overcorrection procedure was introduced contingent upon inappropriate hand movements during a free-play period, and later contingent upon inappropriate vocalizations at naptime. “Hand” overcorrection was withdrawn and then re-introduced sequentially for both behaviors. Several concurrent behaviors were measured to assess multiple effects of treatment. Results for both children indicated the “hand” overcorrection procedure suppressed inappropriate hand movements and inappropriate behaviors that were topographically dissimilar. In addition, inverse relationships were observed between the second child's inappropriate hand movements and appropriate toy usage during free play and between his inappropriate vocalizations and inappropriate foot movements during naptime. Results suggest that overcorrection procedures that are effective for one behavior can be used to reduce the frequency of topographically different behaviors. This finding is discussed in terms of its practical implications for therapists.     

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.     

Symbolic Insight and Inhibitory Control: Two Problems Facing Young Children on Symbolic Retrieval Tasks

Many recent studies have explored young children's ability to use information from physical representations of space to guide search within the real world. In one commonly used procedure, children are asked to find a hidden toy in a room after observing a smaller toy being hidden in the analogous location in a scale model of the room. Three-year-old children readily find the hidden toy, although children at 2.5 years often have difficulty with the task. This experiment examined the causes of 2.5-year-olds' difficultly with this symbol system by incorporating testing procedures previously used with chimpanzees. Results indicate that young children's poor performance primarily stems from a difficulty achieving symbolic insight (i.e., recognizing the model-room representational relationship) but is also strongly affected by deficits in inhibitory control.     

Are infants in the dark about hidden objects?

Infants appear to search for objects hidden by darkness earlier in development than they search for objects hidden by an occluder in the light. However, these two types of search tasks have differed in numerous ways that may have contributed to better performance in the dark (e.g. in whether the hidden objects made sound, in the number of familiarization trials with visible objects). The current studies controlled such incidental differences between search tasks, so that they could be directly compared. Six‐and‐a‐half‐month‐olds received four types of test events, in which either a toy or no toy was presented and then hidden in the dark or under a cloth in the light. Infants searched more often on toy than no‐toy trials in the dark than with a cloth. The advantage in searching for hidden objects in the dark thus appears to be genuine. Theoretical implications are discussed.     

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.     

Toy-oriented changes during early arm movements IV: shoulder-elbow coordination

Our recent work on the initial emergence of reaching identified a mosaic of developmental changes and consistencies within the hand and joint kinematics of arm movements across the pre-reaching period. The purpose of this study was to test hypotheses regarding the coordination of hand and joint kinematics over this same pre-reaching period. Principal component analysis (PCA) was conducted on hand, shoulder, and elbow kinematic data from 15 full-term infants observed biweekly from 8 weeks of age through the week of reach onset. Separate PCAs were calculated for spatial variables and for velocity variables in trials with a toy and without a toy. From the PCA results, we constructed ‘variance profiles’ to reflect the coordinative structure of the hand, shoulder, and elbow. By coordinative structure is meant here the relative contribution of each joint to the factors revealed by the PCA. Shifts in these profiles, which reflected coordination changes, were compared across the hand and joints within each pre-reaching phase (Early, Mid, Late) as well as across phases and trial conditions (no-toy and toy). Results identified both surprising consistencies and important developmental changes in coordination. First, over development, spatial coordination changed in different ways for the shoulder and elbow. Between the Early and Late phases, spatial coordination at the shoulder showed more adult-like coordination during both spontaneous movements and movements with a toy present. In contrast, elbow spatial coordination became more adult-like only during movements with a toy and less adult-like during spontaneous movements. Second, over development, velocity coordination became more adult-like at both joints in movements with and without a toy present. We propose that the features of coordination that changed over development suggest explanations for the differential roles and developmental trajectories of the control of arm movements between the shoulder and elbow. We propose that features that remained consistent over development suggest the presence of developmentally important constraints inherent in arm biomechanics, which may simplify arm control for reaching. Taken together, these findings highlight the critical role of spontaneous arm movements in the emergence of purposeful reaching.     

Transition to success on the model room task: the importance of improvements in working memory

Previous work has shown that children under age 3 often perform very poorly on the model room task, in which they are asked to find a hidden toy based on its location in a scale model. One prominent theory for their failure is that they lack the ability to understand the model as both a physical object and as a symbolic representation of the larger room. A hypothesized additional component is that they need to overcome weak, competing representations of where the object was on a previous trial, and where it is in the present trial, in order to succeed in their search. Children aged 33–39 months were tested on the model room task, as well as on measures of cognitive inhibitory control, cognitive flexibility, and working memory. Results showed that performance on the model room task was not predicted by measures of inhibitory control or cognitive flexibility, but was predicted by performance on the Delayed Recognition Span Test (DRST), a measure of working memory. These findings lend support to the theory of competing representations and demonstrate the necessity of updating and maintaining strong representations in working memory to succeed in the search task.     

A computational and neuropsychological account of object-oriented behaviours in infancy

Infants under 7 months of age fail to reach behind an occluding screen to retrieve a desired toy even though they possess sufficient motor skills to do so. However, even by 3.5 months of age they show surprise if the solidity of the hidden toy is violated, suggesting that they know that the hidden toy still exists. We describe a connectionist model that learns to predict the position of objects and to initiate a response towards these objects. The model embodies the dual-route principle of object information processing characteristic of the cortex. One route develops a spatially invariant surface feature representation of the object whereas the other route develops a feature blind spatial–temporal representation of the object. The model provides an account of the developmental lag between infants’ knowledge of hidden objects and their ability to demonstrate that knowledge in an active retrieval task, in terms of the need to integrate information across multiple object representations using (associative) connectionist learning algorithms. Finally, the model predicts the presence of an early dissociation between infants’ ability to use surface features (e.g. colour) and spatial–temporal features (e.g. position) when reasoning about hidden objects. Evidence supporting this prediction has now been reported.     

Causal learning from probabilistic events in 24‐month‐olds: an action measure

How do young children learn about causal structure in an uncertain and variable world? We tested whether they can use observed probabilistic information to solve causal learning problems. In two experiments, 24‐month‐olds observed an adult produce a probabilistic pattern of causal evidence. The toddlers then were given an opportunity to design their own intervention. In Experiment 1, toddlers saw one object bring about an effect with a higher probability than a second object. In Experiment 2, the frequency of the effect was held constant, though its probability differed. After observing the probabilistic evidence, toddlers in both experiments chose to act on the object that was more likely to produce the effect. The results demonstrate that toddlers can learn about cause and effect without trial‐and‐error or linguistic instruction on the task, simply by observing the probabilistic patterns of evidence resulting from the imperfect actions of other social agents. Such observational causal learning from probabilistic displays supports human children's rapid cultural learning.     

Toddlers’ social evaluations of agents who act on false beliefs

Mature social evaluations privilege agents’ intentions over the outcomes of their actions, but young children often privilege outcomes over intentions in verbal tasks probing their social evaluations. In three experiments (N = 118), we probed the development of intention-based social evaluation and mental state reasoning using nonverbal methods with 15-month-old toddlers. Toddlers viewed scenarios depicting a protagonist who sought to obtain one of two toys, each inside a different box, as two other agents observed. Then, the boxes’ contents were switched in the absence of the protagonist and either in the presence or the absence of the other agents. When the protagonist returned, one agent opened the box containing the protagonist's desired toy (a positive outcome), and the other opened the other box (a neutral outcome). When both agents had observed the toys move to their current locations, the toddlers preferred the agent who opened the box containing the desired toy. In contrast, when the agents had not seen the toys move and therefore should have expected the desired toy's location to be unchanged, the toddlers preferred the agent who opened the box that no longer contained the desired toy. Thus, the toddlers preferred the agent who intended to make the protagonist's desired toy accessible, even when its action, guided by a false belief concerning that toy's location, did not produce a positive outcome. Well before children connect beliefs to social behavior in verbal tasks, toddlers engage in intention-based evaluations of social agents with false beliefs.     

The effect of spatial cues on infants’ responses in the AB task,with and without a hidden object

The errors made by infants in the AB task were taken by Piaget as an indication of an inability to update their representations of the spatial location of a hidden object. This paper presents an experiment designed to further investigate the role of spatial representations in the production of the error. The introduction of strong visual cues to spatial location was found to reduce the traditional A‐not‐B search error. However, it also increased perseveration when a ‘lids‐only’ analogue of the AB task was used, in which infants are simply cued to pick up lids rather than encouraged to search for a hidden object. These results present a challenge to the dynamic systems account of the error given by Smith, Thelen, Titzer and McLin (Psychological Review, 106 (1999), 235–260), and indicate that the traditional A‐not‐B search error arises from a difficulty in updating representations of the spatial location of hidden objects. The relation of these results to Munakata’s PDP model (Developmental Science, 1 (1998), 161–211) and Thelen, Schöner, Scheier and Smith’s (Behavioural and Brain Sciences, 24 (2001), 1‐‐86) most recent dynamic systems model of the A‐not‐B error is also discussed.