The development of sensitivity to biological motion in noise

We investigated developmental changes in sensitivity to biological motion by asking 6-year-olds, 9-year-olds, and adults (twenty-four in each group) to discriminate point-light biological motion displays depicting one of a variety of human movements from scrambled versions of the same displays. When tested without noise dots, participants at all ages performed near ceiling levels and no differences in accuracy were found among the three age groups. Age differences emerged in the second task, in which we used a staircase procedure to determine threshold values of the number of noise dots that could be tolerated in producing a percentage correct value corresponding to a d' value of 1.4. Sensitivity to biological motion improved linearly with age (p < 0.01), with 6-year-olds performing significantly more poorly than adults. This immature performance contrasts with adult-like accuracy by 4 years of age for sensitivity to global motion (Parrish et al, 2005 Vision Research 45 827-837). The comparison implies an immaturity at 6 years of age in the neural networks involved specifically in the processing of biological motion, networks that may include the superior temporal sulcus (STS).     

Detection of glass patterns by pigeons and humans: implications for differences in higher-level processing

Glass patterns have been used to examine mechanisms underlying form perception. The current investigation compared detection of Glass patterns by pigeons and humans and provides evidence for substantial species differences in global form perception. Subjects were required to discriminate, on a simultaneous display, a random dot pattern from a Glass pattern. Four different randomly presented Glass patterns were used (concentric, radial, parallel-vertical, and parallel-horizontal). Detection thresholds were measured by degrading the Glass patterns through the addition of random noise. For both humans and pigeons, discrimination decreased systematically with the addition of noise. Humans showed detection differences among the four patterns, with lowest thresholds to radial and concentric patterns and highest thresholds to the parallel-horizontal pattern. Pigeons did not show a detection difference across the four patterns. Implications for differences in neural processing of complex forms are discussed.     

Spatial integration in Glass patterns

The extraction of a global orientation structure presumably has a different neural mechanism from that of the analysis of its local features. We investigated spatial integration within these two mechanisms using stimulus patterns composed of dot pairs (dipoles). The stimuli targeted local feature detection, contained no global configuration, but rather contained randomly oriented dipoles of a fixed length (the distance between the dots in a pair). For the detection of a global orientation structure, local dipole orientations were arranged in a concentric Glass pattern. Thresholds as a function of a stimulus area were determined by measuring the minimum proportion of dipoles among random-dot noise (signal-to-noise ratio) required for the detection of dipoles (features), as well as for the detection of an orientation structure. Thresholds for feature detection were significantly higher than those for the detection of the global structure--regardless of the stimulus size. Spatial integration, however, did not differ between the two tasks: the exponents of the power functions fitted to data for six observers were -0.48 +/- 0.07 for random dipole orientations and -0.62 +/- 0.1 for Glass patterns.     

Some observations on the perception of Marroquin patterns.

Demonstrations are presented to show that the perception of structure in Marroquin patterns is disrupted if the dots comprising the pattern have opposite contrast polarity, and also if the dots comprising the pattern are separated in stereoscopic depth. It is also demonstrated that the perception of structure in a Marroquin pattern is made possible if the pattern is separated in stereoscopic depth from 'noise' dots, where the pattern structure cannot be perceived in either half of the unfused stereogram. In these respects the perception of Marroquin patterns is similar to the perception of Glass patterns. These findings are thus consistent with the proposal that the perception both of Marroquin and of Glass patterns is based on the construction of virtual lines.     

Developmental changes in the processing of hierarchical shapes continue into adolescence

The present study was designed to trace the normal development of local and global processing of hierarchical visual forms. We presented pairs of hierarchical shapes to children and adults and asked them to indicate whether the two shapes were the same or different at either the global or the local level. In Experiments 1 (6-year-olds, 10-year-olds, adults) and 2 (10-year-olds, 14-year-olds, adults), we presented stimuli centrally. All age groups responded faster on global trials than local trials (global precedence effect), but the bias was stronger in children and diminished to the adult level between 10 and 14 years of age. In Experiment 3 (10-year-olds, 14-year-olds, adults), we presented stimuli in the left or right visual field so that they were transmitted first to the contralateral hemisphere. All age groups responded faster on local trials when stimuli were presented in the right visual field (left hemisphere); reaction times on global trials were independent of visual field. The results of Experiment 3 suggest that by 10 years of age the hemispheres have adult-like specialization for the processing of hierarchical shapes, at least when attention is directed to the global versus local level. Nevertheless, their greater bias in Experiments 1 and 2 suggests that 10-year-olds are less able than adults to modulate attention to the output from local versus global channels-perhaps because they are less able to ignore distractors and perhaps because the cerebral hemispheres are less able to engage in parallel processing.     

Long trajectory for the development of sensitivity to global and biological motion

We used a staircase procedure to test sensitivity to (1) global motion in random-dot kinematograms moving at 4° and 18° s(-1) and (2) biological motion. Thresholds were defined as (1) the minimum percentage of signal dots (i.e. the maximum percentage of noise dots) necessary for accurate discrimination of upward versus downward motion or (2) the maximum percentage of noise dots tolerated for accurate discrimination of biological from non-biological motion. Subjects were adults and children aged 6-8, 9-11, and 12-14 years (n = 20 per group). Contrary to earlier research, results revealed a similar, long developmental trajectory for sensitivity to global motion at both slower and faster speeds and for biological motion. Thresholds for all three tasks improved monotonically between 6 and 14 years of age, at which point they were adult-like. The results suggest that the extrastriate mechanisms that integrate local motion cues over time and space take many years to mature.     

Detecting structure in glass patterns: an interocular transfer study

Glass patterns are visual stimuli used here to study how local orientation signals are spatially integrated into global pattern perception. We measured a form aftereffect from adaptation to both static and dynamic Glass patterns and calculated the amount of interocular transfer to determine the binocularity of the detectors responsible for the perception of global structure. Both static and dynamic adaptation produced significant form aftereffects and showed a very high degree of interocular transfer, suggesting that Glass-pattern perception involves cortical processing beyond primary visual cortex. Surprisingly, dynamic adaptation produced significantly greater interocular transfer than static adaptation. Our results suggest a functional interaction between local orientation processing and global motion processing that contributes to form perception.     

Gradual improvement in fine-grained sensitivity to triadic gaze after 6 years of age

The current research compared the ability of adults and children to determine where another person is looking in shared visual space (triadic gaze). In Experiment 1, children (6-, 8-, 10-, and 14-year-olds) and adults viewed photographs of a model fixating a series of positions separated by 1.6° along the horizontal plane. The task was to indicate whether the model was looking to the left or right of one of three target positions (midline, 6.4° left, or 6.4° right). By 6 years of age, thresholds were quite small (M=1.94°) but were roughly twice as large as those of adults (M=1.05°). Thresholds decreased to adult-like levels around 10 years of age. All age groups showed the same pattern of higher sensitivity for central targets than peripheral targets and of misjudging gaze toward peripheral targets as farther from midline than it really was. In subsequent experiments, we evaluated possible reasons for the higher thresholds in 6- and 8-year-olds. In Experiment 2, the thresholds of 6-year-olds did not improve when the range of deviations from the target position that the model fixated covered a much wider range. In Experiment 3, 8-year-olds were less sensitive than adults to small shifts in eye position even though the task required only matching faces with the same eye position and not determining where the person was looking. These findings suggest that by 6 years of age, children are quite sensitive to triadic gaze, which may support inferences about others' interests and intentions. Subsequent improvements in sensitivity involve, at least in part, an increase in sensitivity to eye position.     

The development of sensitivity to visual structure.

Perceived complexity of visual patterns as a function of stimulus structure and contour was studied in 4–5-, 7–8-, and 9–10-yr-old children and adults. Subjects participated in a paired comparison task of visual complexity. Both amount of contour and the presence or absence of structure in the patterns were manipulated The results indicated that complexity judgments of all subjects were affected by the presence of structure at lower levels of contour. With age, gradually increasing weight was attributed to visual structure in high-contour patterns. The results suggested that sensitivity to visual structure may develop well into school age, taking the form of a gradual increase in the number of pattern elements which can be perceived to be organized.     

Global dot integration in typically developing children and in Williams Syndrome

Williams Syndrome (WS) is a neurodevelopmental disorder that results in deficits in visuospatial perception and cognition. The dorsal stream vulnerability hypothesis in WS predicts that visual motion processes are more susceptible to damage than visual form processes. We asked WS participants and typically developing children to detect the global structure Glass patterns, under “static” and “dynamic” conditions in order to evaluate this hypothesis. Sequentially presented Glass patterns are coined as dynamic because they induce illusory motion, which is modeled after the interaction between orientation (form) and direction (motion) mechanisms. If the dorsal stream vulnerability holds in WS participants, then they should process real and illusory motion atypically. However, results are consistent with the idea that form and motion integration mechanisms are functionally delayed or attenuated in WS. Form coherence thresholds for both static and dynamic Glass patterns in WS were similar to those of 4–5 year old children, younger than what is predicted by mental age. Dynamic presentation of Glass patterns improved thresholds to the same degree as typical participants. Motion coherence thresholds in WS were similar to those of mental age matches. These data pose constraints on the dorsal vulnerability hypothesis, and refine our understanding of the relationship between form and motion processing in development.     

Global dot integration in typically developing children and in Williams Syndrome

Williams Syndrome (WS) is a neurodevelopmental disorder that results in deficits in visuospatial perception and cognition. The dorsal stream vulnerability hypothesis in WS predicts that visual motion processes are more susceptible to damage than visual form processes. We asked WS participants and typically developing children to detect the global structure Glass patterns, under “static” and “dynamic” conditions in order to evaluate this hypothesis. Sequentially presented Glass patterns are coined as dynamic because they induce illusory motion, which is modeled after the interaction between orientation (form) and direction (motion) mechanisms. If the dorsal stream vulnerability holds in WS participants, then they should process real and illusory motion atypically. However, results are consistent with the idea that form and motion integration mechanisms are functionally delayed or attenuated in WS. Form coherence thresholds for both static and dynamic Glass patterns in WS were similar to those of 4–5 year old children, younger than what is predicted by mental age. Dynamic presentation of Glass patterns improved thresholds to the same degree as typical participants. Motion coherence thresholds in WS were similar to those of mental age matches. These data pose constraints on the dorsal vulnerability hypothesis, and refine our understanding of the relationship between form and motion processing in development.     

Concept learning,memory and transfer of dot pattern categories

In the first experiment, subjects rated the similarity of a sample of pairs of random dot patterns generated from 3 prototypes consisting of either 4, 6, or 9 dots. The results of the experiment tended to confirm the structure imposed on the patterns by the construction method. In the second experiment, subjects learned to classify random patterns generated from 2 prototypes with either short or long interprototype distance and consisting of either 4, 6, or 9 dots in a traditional concept identification task. After acquisition, memory for old and new distortions and the prototype, which was not presented during learning, was assessed. The tendency to call a pattern “new” increased with the distance between the pattern and its prototype. In a subsequent transfer test, all subjects saw patterns of either 4, 6, or 9 dots. Performance was above chance and the transfer from larger to smaller patterns tended to be greater than the transfer from smaller to larger patterns. This is consistent with a process of schema formation based on features common to most exemplars of the category. The results are discussed in relation to several theories of concept learning and schema abstraction.     

A Longitudinal Study of Semantic Grouping Strategy Use in 6–11-Year-Old Children: Investigating Developmental Phases,the Role of Working Memory,and Strategy Transfer

This two-cohort longitudinal study on the development of the semantic grouping strategy had three goals. First, the authors examined if 6–7-year-olds are nonstrategic before becoming strategic after prompting at 8–9 years of age, and if 8–9-year-olds are prompted strategic before spontaneous strategy use at 10–11 years of age. Children 6–7 and 8–9 years old performed two sort-recall tasks (one without and one with a grouping prompt) at two time points separated 1.5 years from each other. Second, the authors investigated whether short-term or working memory capacity at time point 1 predicted recall in children who did or did not use the semantic grouping strategy 1.5 years later. Third, the authors investigated whether prompted strategic children and children who used the strategy spontaneously differed in strategy transfer to a new task. Developmental results confirmed previous cross-sectional results, but in a longitudinal two-cohort study 6–7-year-olds were nonstrategic, and became prompted strategic around 8–9 years of age, followed by spontaneous strategy use at age 10–11 years. The authors found that memory capacity was not predictive of later use of the strategy. New findings were that prompted strategic children were as equally able as spontaneously strategic children to transfer the strategy to a new task, albeit with smaller recall benefits.     

Bimanual stereotypes: bimanual coordination in children as a function of movements and relative velocity

Five-, 7-, and 9-year-old children were trained and tested in a bimanual coordination task that required them to rotate two cranks (either at the same or at different velocities) using mirror (inwards or outwards) or parallel movements (clockwise or counterclockwise). The task consisted of tracing two lines of different slants, by turning the two cranks either at the same velocity (to draw the 45 degrees slanted line) or at different velocities (to draw the 22 degrees line). The same-velocity condition resulted in significantly better performance than the different-velocities condition with the age x angle interaction: the performance in the different-velocities condition improved considerably at 9 years of age. Mirror movement induced faster and more accurate performance relative to parallel movements in the same-velocity condition but not in the different-velocities condition. This difference was much greater in 5- and 7-year-olds than in 9-year-olds. The results are interpreted as reflecting a decreasing influence of motor constraints on bimanual coordination.     

The height + width = area of a rectangle rule in five-year-olds: effects of stimulus distribution and graduation of the response scale.

This study attempts to account for disparities between the Anderson and Cuneo (1978), Leon (1982), and Lautrey, Mullet, and Paques (1989) studies in regard to children's area judgment. Two task variables were manipulated: stimulus distribution (biased/unbiased) and the type of response scale (graduated/ungraduated). Three age groups (5, 6, and 7 year olds) were tested. The mean integration pattern for 5-year-olds presented a negatively biased stimulus distribution, and an ungraduated response scale was highly convergent and suggested the use of a centration rule (replication of the Lautrey et al. results). When 5-year-olds were presented with an unbiased stimulus distribution and a graduated scale, the integration pattern was only slightly convergent (as in Leon). The effects of two factors (age and graduation) were significant and combined additively: The older the child, the more graduated the response scale and the more the integration pattern tended to form three ascending parallel lines (the Anderson & Cuneo results).     

Visual form-processing deficits in autism

People with autism have a number of reported deficits in object recognition and global processing. Is there a low-level spatial integration deficit associated with this? We measured spatial-form-coherence detection thresholds using a Glass stimulus in a field of random dots, and compared performance to a similar motion-coherence task. A coherent visual patch was depicted by dots separated by a rotational transformation in space (form) or space-time (motion). To measure parallel visual integration, stimuli were presented for only 250 ms. We compared detection thresholds for children with autism, children with Asperger syndrome, and a matched control group. Children with autism showed a significant form-coherence deficit and a significant motion-coherence deficit, while the performance of the children with Asperger syndrome did not differ significantly from that of controls on either task.     

Tell-tale eyes: children's attribution of gaze aversion as a lying cue

This study examined whether the well-documented adult tendency to perceive gaze aversion as a lying cue is also evident in children. In Experiment 1, 6-year-olds, 9-year-olds, and adults were shown video vignettes of speakers who either maintained or avoided eye contact while answering an interviewer's questions. Participants evaluated whether the speaker was telling the truth or lying on each trial. The results revealed that at both ages, children were more likely to attribute lying to speakers in the gaze aversion condition; however, the effect was significantly greater among 9-year-olds. Significant gender differences were also uncovered, with girls demonstrating strongest sensitivity to the gaze cue. Experiment 2 replicated the gender effect in 6-year-olds but found that when the speakers' verbal responses were removed, boys' use of the gaze cue increased and the gender difference disappeared. These findings indicate that at 6 years old, children interpret interpersonal gaze behavior as a socially informative cue. Furthermore, the growing appreciation of the stereotypic gaze behavior associated with lying and the reputed female advantage in gaze sensitivity may reflect differential processing of multimodal communication.     

Fears, worries, and scary dreams in 4- to 12-year-old children: their content, developmental pattern, and origins

Investigated anxiety symptoms in normal school children 4 to 12 years of age (N = 190). The percentages of children reporting fears, worries, and scary dreams were 75.8, 67.4, and 80.5%, respectively, indicating that these anxiety symptoms are quite common among children. Inspection of the developmental pattern of these phenomena revealed that fears and scary dreams were common among 4- to 6-year-olds, became even more prominent in 7- to 9-year-olds, and then decreased in frequency in 10- to 12-year-olds. The developmental course of worry deviated from this pattern. This phenomenon was clearly more prevalent in older children (i.e., 7- to 12-year-olds) than in younger children. Furthermore, although the frequency of certain types of fears, worries, and dreams were found to change across age groups (e.g., the prevalence of fears and scary dreams pertaining to imaginary creatures decreased with age, whereas worry about test performance increased with age), the top intense fears, worries, and scary dreams remained relatively unchanged across age levels. An examination of the origins of these common anxiety phenomena showed that for fears and scary dreams, information was the most commonly reported pathway, whereas for worry, conditioning experiences were more prominent.     

Developing motor planning over ages

Few studies have explored the development of response selection processes in children in the case of object manipulation. In the current research, we studied the end-state comfort effect, the tendency to ensure a comfortable position at the end rather than at the beginning of simple object manipulation tasks. We used two versions of the unimanual bar transport task. In Experiment 1, only 10-year-olds reached the same level of sensitivity to end-state comfort as adults, and 8-year-olds were less efficient than 6-year-olds. In each age group, children’s sensitivity did not increase during a session: i.e., either clearly showed the sensitivity or showed no sensitivity at all. Experiment 2 replicated these results when the bar was replaced by a pencil and when the task did not require much precision. However, when the task required more precision, 8-year-olds increased their level of sensitivity to the end-state comfort effect, whereas this was not the case for younger children. These results describe the development of advanced planning processes from 4 to 10 years of age as well as the positive effect of task constraints on the end-state comfort effect for 8-year-olds.     

Global processing speed as a mediator of developmental changes in children's auditory memory span

This study examined the role of global processing speed in mediating age increases in auditory memory span in 5- to 13-year-olds. Children were tested on measures of memory span, processing speed, single-word speech rate, phonological sensitivity, and vocabulary. Structural equation modeling supported a model in which age-associated increases in processing speed predicted the availability of long-term memory phonological representations for redintegration processes. The availability of long-term phonological representations, in turn, explained variance in memory span. Maximum speech rate did not predict independent variance in memory span.