The modulation of visual orienting reflexes across the lifespan

The development of reflexive and voluntary shifts of visual attention, as well as relations between the two forms of shifting, were examined in three groups of children (5, 7, and 9 years old), one group of young adults (24 years old), and two groups of senior adults (young seniors with an average age of 69 years, and old seniors with an average age of 81 years). The task entailed response to the detection of a target (black dot) in one of four possible locations in the visual field. Relations between reflexive and voluntary shifts of attention were gauged by the degree to which flash and arrow facilitation and inhibition were observed in response to the presentation of both arrow and flash cues together in one trial. All age groups oriented reflexively in response to a flash cue and utilized the arrow cue to orient attention strategically. When flash and arrow cues were presented in quick succession and thereby competed for attention, the youngest children and oldest seniors were least efficient and flexible in their approach to the orienting task as they had difficulty modulating visual reflexes.     

Visual experiences during letter production contribute to the development of the neural systems supporting letter perception

Letter production through handwriting creates visual experiences that may be important for the development of visual letter perception. We sought to better understand the neural responses to different visual percepts created during handwriting at different levels of experience. Three groups of participants, younger children, older children, and adults, ranging in age from 4.5 to 22 years old, were presented with dynamic and static presentations of their own handwritten letters, static presentations of an age‐matched control's handwritten letters, and typeface letters during fMRI. First, data from each group were analyzed through a series of contrasts designed to highlight neural systems that were most sensitive to each visual experience in each age group. We found that younger children recruited ventral‐temporal cortex during perception and this response was associated with the variability present in handwritten forms. Older children and adults also recruited ventral‐temporal cortex; this response, however, was significant for typed letter forms but not variability. The adult response to typed letters was more distributed than in the children, including ventral‐temporal, parietal, and frontal motor cortices. The adult response was also significant for one's own handwritten letters in left parietal cortex. Second, we compared responses among age groups. Compared to older children, younger children demonstrated a greater fusiform response associated with handwritten form variability. When compared to adults, younger children demonstrated a greater response to this variability in left parietal cortex. Our results suggest that the visual perception of the variability present in handwritten forms that occurs during handwriting may contribute to developmental changes in the neural systems that support letter perception.     

A developmental study of visual attention: Issues of filtering efficiency and focus

A forced-choice reaction time (RT) task was used to assess developmental changes in filtering and the concomitant ability to narrow the focus of the attentional lens. Participants included 20 children in each of four age groups (4, 5, 7, and 9 years), as well as 20 adults between the ages of 21 and 29 years. Conditions varied with regard to the presence or absence of distractors and their proximity to a target stimulus, and the presence or absence of a visual window within which the target stimulus was presented. Age-related differences in the ability to filter task-irrelevant stimuli were found. The performance of 4-year-old children was adversely affected with the presence of distractors located at both 5.7° and 0.95° of visual angle from target stimuli, whereas that of children aged 5, 7, and 9 was negatively affected only with distractors 0.95° of visual angle from the target. Adults' performance was not adversely affected by the presence of distractors. Developmental differences in focusing attention were further highlighted by the finding that the presence of a visual window cue was only associated with faster RTs among 4-year-old children. These results are discussed in terms of the zoom-lens metaphor of visual attention, and the development of the ability to vary the size of an attentive zoom-lens in response to task requirements.     

Rapid discrimination of visual patterns in children and adults

Rapid visual discrimination in children (9 to 11 yr.) and adults was investigated using two tasks in which the subject had to search for a target pattern embedded in 35 background patterns. The time available for inspecting the search arrays was altered by varying the stimulus duration. In one task, there was a large difference in the feature or 'texton' content of patterns between the target and the background; in the other, this difference was small. In the first task, the children could detect the target pattern in a briefly flashed search array with high accuracy, because the target 'popped out' perceptually from the array, but in the second task the same detection rate was not reached until the stimulus duration was much longer, since a serial searching strategy was required. Results achieved by children and adults were similar. It seems that serial visual search is as efficient in children as in adults.     

The effects of onset and offset warning and post-target stimuli on the saccade latency of children and adults

Two studies, involving children (mean age = 10 years) and adults, investigated the effects of visual stimulus onsets and offsets on the latency of saccades to peripheral targets. Saccade latency was reduced when foveal stimulus onsets or offsets preceded the target. When stimulus onset occurred 100 msec after target onset, the stimulus interfered with responding, with this interference effect significantly greater for children than for adults. When stimuli were presented in the peripheral visual field facilitation and interference effects were similar for children and adults. These results were interpreted as indicating that oculomotor processes are similar in children and adults while the stimulus intake processes that follow stimulus onset at the point of fixation have a greater interference effect on children's than on adults' eye movements.     

A psychophysical measure of visual and kinaesthetic spatial discriminative abilities of adults and children

Quantitative estimates of the spatial discriminative capacities of the visual and kinaesthetic systems in adults and children were obtained. Intersensory integration was investigated by including spatial discriminations based on congruent visual plus kinaesthetic reafference. The psychophysical method of adjustment was used with simultaneous comparisons of a fixed and a variable stimulus. The subject's task was to estimate when the variable stimulus (ellipse) was identical to the standard one (circle), under one of three modality conditions: vision, kinaesthesis, and vision plus kinaesthesis. After a pilot study with adults, children (aged 8, 10, and 12 years) and adults were both tested. Subjects from each age group were randomly allocated to each of the three experimental conditions. Results show that the visual and kinaesthetic estimates of the 8- and 10-year-old subjects did not differ significantly, but the visual responses of the adults and 12 year olds were significantly more accurate than corresponding kinaesthetic estimates. Bisensory estimates were significantly more accurate than visual responses only for the 8- and 10-year-old age groups. Intramodal comparisons showed the kinaesthetic estimates of the 8, 10, and 12 year olds to be significantly more accurate than the corresponding adult performance. Adult visual estimates were significantly more accurate than those made by 8 year olds, but were not significantly different from the visual responses of 10 and 12 year olds. Estimates based on bisensory reafference did not differ from each other across the four age groups. It is concluded that modality adeptness and dominance are task dependent and empirically determined rather than being innate properties of sensory systems. The data indicate that intersensory differentiation rather than integration occurs with maturity.     

Locomotor estimation of distance after visual scanning by children and adults

Subjects (120 young adults and 120 children) were tested for their abilities to estimate visually the distance to a target 5 m away, then walk unaided by vision to that target as accurately as possible. Experimental groups were determined by visual scanning time (1, 5, or 10 s), delay between the end of visual scanning and the start of locomotion (0, 1, 3, or 5 s), and by age (9 year old children or young adult). Adults performed locomotor distance estimations based on visual scanning more accurately than children under all conditions. Increased scanning time resulted in more accurate performances by children but not by adults, and increased delays between the end of scanning and the start of locomotion caused decreases in accuracy for children only. These decrements were partially ameliorated by increased scanning time. The total time spent without vision after scanning the target (delay time plus walking time) was an important factor, with sharp increases in error for all delay conditions for children. The results are discussed in terms of trace decay effects and developmental aspects of visual guidance of locomotion.     

The development of selective inhibitory control: The influence of verbal labeling

The role of language in the development of selective inhibitory control was examined in four groups: Children aged 7-9 years, children aged 11-13 years, adults aged 20-27 years, and adults aged 62-76 years. We used a modified stop-signal task in which participants inhibited or executed responses based on a visual signal. Response execution and inhibition were assessed by measurement of reaction times (RTs) and error rates to a go signal and RTs to a stop signal. Four task variations were compared in which subjects named (1) the stimulus, (2) the intended action (go/stop), (3) something irrelevant, or (4) nothing. Results showed different developmental trends for response execution and inhibition across the lifespan. Moreover, response execution was faster and more accurate when subjects named the stimulus instead of the intended action. The increase in response accuracy when naming the stimulus was greatest for children. In contrast to expectations, naming the intended action did not influence response inhibition. Overall, these findings suggest that verbal labeling supports the initiation but not the inhibition of actions.     

The development of visual information processing skills related to reading

Literate adults can use their familiarity with specific words and their knowledge of English orthography to facilitate word recognition processes. The development of word superiority effects in visual perception was investigated in the present study using a search task with kindergarten (5.7 years old), second (8.0 years old), and fourth grade children (10.0 years old), and college students. The search task consisted of the visual presentation of a target letter followed by a three-, four-, or five-letter display. The target letter was included in the display on half the trials, and the displays were common words, orthographically regular pseudowords, and irregular nonwords. Although response times decreased with age, the three oldest groups showed similar effects for the size and structure of the displays. That is, response times increased linearly with the number of display letters, and responses were faster for word and pseudoword displays than for nonwords. The data for the kindergarten children showed evidence for the use of a different search strategy, and they did not respond differentially to the three types of displays. The results are discussed in terms of the implications for developmental models of visual search and word superiority effects in visual perception.     

Object processing for action across childhood

Human adults process and select the opportunities for action in their environment rapidly, efficiently, and effortlessly. While several studies have revealed substantial improvements in object recognition skills, motor abilities, and control over the motor system during late childhood, surprisingly little is known about how object processing for action develops during this period. This study addresses this issue by investigating how the ability to ignore actions potentiated by a familiar utensil develops between ages 6 and 10 years. It is the first study to demonstrate that (1) the mechanisms that transform a graspable visual stimulus into an object‐appropriate motor response are in place by the sixth year of life and (2) graspable features of an object can facilitate and interfere with manual responses in an adult‐like manner by this age. The results suggest that there may be distinct developmental trajectories for the ability to ignore motor responses triggered by visual affordances and the stimulus response compatibility effects typically assessed with Simon tasks.     

Parallel development of ERP and behavioural measurements of visual segmentation

Visual segmentation, a process in which elements are integrated into a form and segregated from the background, is known to differ from adults at infancy. The further developmental trajectory of this process, and of the underlying brain mechanisms, during childhood and adolescence is unknown. The aim of the study was to investigate the developmental trajectory of ERP reflections of visual segmentation, and to relate this to behavioural performance. One hundred and eleven typically developing children from 7 to 18 years of age were divided into six age groups. Each child performed two visual tasks. In a texture segmentation task, the difference in event‐related potential (ERP) response to homogeneous (no visual segmentation) and checkered stimuli (visual segmentation) was investigated. In addition, behavioural performance on integration of elements into contours was measured. Both behavioural and ERP measurements of visual segmentation differed from adults in 7–12 year‐old children. Behaviourally, young children were less able to integrate elements into a contour than older children. In addition, a developmental change was present in the ERP pattern evoked by homogeneous versus checkered stimuli. The largest differences in behaviour and ERPs were found between 7–8‐ and 9–10‐, and between 11–12‐ and 13–14‐year‐old children, indicating the strongest development between those age groups. Behavioural as well as ERP measurements at 13–14 years of age showed similar results to those of adults. These results reveal that visual segmentation continues to develop until early puberty. Only by 13–14 years of age, children do integrate and segregate visual information as adults do. These results can be interpreted in terms of functional connectivity within the visual cortex.     

The race that precedes coactivation: development of multisensory facilitation in children

Rationale: The facilitating effect of multisensory integration on motor responses in adults is much larger than predicted by race‐models and is in accordance with the idea of coactivation. However, the development of multisensory facilitation of endogenously driven motor processes and its relationship to the development of complex cognitive skills in school‐age children is largely unexplored. Method: Twenty adults and 95 children where allocated into six age groups: 6, 7, 8, 9, 10–11 and adults. Participants’ motor reaction times (MRTs) and accuracy in response to the detection of auditory, visual and audiovisual stimuli were recorded. Children's reading accuracy and nonverbal IQ were also assessed. Results: In general, MRTs of children were significantly slower with greater variability than those of adults. Although the average level of multisensory facilitation was similar for all age groups, mean cumulative density functions (CDFs) showed that multisensory facilitation in 6 and 10–11‐year‐olds is within the predictive limits of race‐models. Where coactivation was seen in the CDF of individual children it was not as strong or as consistent as that in adults. The degree of multisensory facilitation did not correlate with age, reading accuracy or IQ. Conclusion: The average level of multisensory facilitation to endogenously driven motor responses does not change gradually with age nor is it related to intelligence or reading accuracy. In general, multisensory integration remains immature until 10–11 years of age and lies within the predicted confines of race‐models.     

The development of rapid online control in children aged 6–12 years: Reaching performance

Rapid online control during reaching has an important bearing on movement accuracy and flexibility. It is surprising then that few studies have investigated the development of rapid online control in children. In this study, we were particularly interested in age-related changes in the nature of motor control in response to visual perturbation. We compared the performance of younger (6–7 years of age), mid-aged (8–9), and older (10–12) children, as well as healthy young adults using a double-step reaching task. Participants were required to make target-directed reaching movements in near space, while also responding to visual perturbations that occurred at movement onset for a small percentage of trials. Results showed that both the older and mid-aged children corrected their reaching in response to the unexpected shifts in target location significantly faster than younger children, manifest by reduced time to correction. In turn, the responses of adults were faster than older children in terms of movement time and on kinematic measures such as time to correction and time to peak velocity. These results indicate that the capacity to utilize forward estimates of limb position in the service of online control of early perturbations to ballistic (or rapid) reaching develops in a non-linear fashion, progressing rapidly between early and middle childhood, showing a degree of stability over mid and later childhood, but then evidence for continued refinement between childhood and young adulthood. The pattern of change after childhood and into early adolescence requires further investigation, particularly during the rapid phase of physical growth that accompanies puberty.     

Thin-slice perception develops slowly

Body language and facial gesture provide sufficient visual information to support high-level social inferences from "thin slices" of behavior. Given short movies of nonverbal behavior, adults make reliable judgments in a large number of tasks. Here we find that the high precision of adults' nonverbal social perception depends on the slow development, over childhood, of sensitivity to subtle visual cues. Children and adult participants watched short silent clips in which a target child played with Lego blocks either in the (off-screen) presence of an adult or alone. Participants judged whether the target was playing alone or not; that is, they detected the presence of a social interaction (from the behavior of one participant in that interaction). This task allowed us to compare performance across ages with the true answer. Children did not reach adult levels of performance on this task until 9 or 10 years of age, and we observed an interaction between age and video reversal. Adults and older children benefitted from the videos being played in temporal sequence, rather than reversed, suggesting that adults (but not young children) are sensitive to natural movement in social interactions.     

Coincidence anticipation of young normal and handicapped children

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.     

The effect of orthographic structure on word recognition in a visual search task

The effect of the orthographic structure of the stimulus field on the visual search performance of third graders (8-8 years), sixth graders (11-7 years) and adults was investigated in three experiments. In Experiment 1, where the predesignated target was one word, subjects of all ages searched equally fast through fields consisting of words, pseudowords, and nonwords. In contrast, subjects of all ages displayed effects of orthographic structure when searching for instances of a semantic category (Experiment 2) or for three words (Experiment 3). Subjects searched faster through nonwords than through pseudowords and faster through pseudowords than through words. The use of orthographic structure to facilitate search did not increase with age, suggesting that children of the youngest age group were already making maximal use of intraword redundancy.     

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.     

Perceptual load influences selective attention across development

Research suggests that visual selective attention develops across childhood. However, there is relatively little understanding of the neurological changes that accompany this development, particularly in the context of adult theories of selective attention, such as N. Lavie's (1995) perceptual load theory of attention. This study examined visual selective attention across development from 7 years of age to adulthood. Specifically, the author examined if changes in processing as a function of selective attention are similarly influenced by perceptual load across development. Participants were asked to complete a task at either low or high perceptual load while processing of an unattended probe stimulus was examined using event related potentials. Similar to adults, children and teens showed reduced processing of the unattended stimulus as perceptual load increased at the P1 visual component. However, although there were no qualitative differences in changes in processing, there were quantitative differences, with shorter P1 latencies in teens and adults compared with children, suggesting increases in the speed of processing across development. In addition, younger children did not need as high a perceptual load to achieve the same difference in performance between low and high perceptual load as adults. Thus, this study demonstrates that although there are developmental changes in visual selective attention, the mechanisms by which visual selective attention is achieved in children may share similarities with adults.     

Motor Processes in Children's Mental Rotation

Previous studies with adult human participants revealed that motor activities can influence mental rotation of body parts and abstract shapes. In this study, we investigated the influence of a rotational hand movement on mental rotation performance from a developmental perspective. Children at the age of 5, 8, and 11 years and adults performed a mental rotation task while simultaneously rotating their hand (guided by a handle). The direction of the manual rotation was either compatible or incompatible with the direction of the mental rotation. Response times increased with increasing stimulus orientation angles, indicating that participants of all age groups used mental rotation to perform the task. A differential effect of the compatibility of manual rotation and mental rotation was found for 5-year-olds and 8-year-olds, but not for 11-year-olds and adults. The results of this study suggest that the ability to dissociate motor from visual cognitive processes increases with age.