Color term knowledge does not affect categorical perception of color in toddlers

Categorical perception of color is shown when colors from the same category are discriminated less easily than equivalently spaced colors that cross a category boundary. The current experiments tested various models of categorical perception. Experiment 1 tested for categorical responding in 2- to 4-year-olds, the age range for the onset establishment of color term knowledge. Experiment 2 tested for categorical responding in Himba toddlers, whose language segments the color space differently from the way in which the English language does so. Experiment 3 manipulated the conditions of the task to explore whether the categorical responding in Experiments 1 and 2 was equivalent to categorical perception. Categorical perception was shown irrespective of naming and was not stronger in those children with more developed color term knowledge. Cross-cultural differences in the extent of categorical perception were not found. These findings support universalistic models of color categorization and suggest that color term knowledge does not modify categorical perception, at least during the early stages of childhood.     

Serial order processing in human infants and the role of multisensory redundancy

Perception, production, and understanding of sequences is fundamental to human behavior and depends, in large part, on the ability to detect serial order. Despite the importance of this issue across many domains of human functioning, the development of serial order skills has been neglected in developmental studies. The current article reviews evidence that the basic temporal and spatiotemporal skills that are necessary for the development of serial order skills emerge early in human development. The article then presents recent evidence from the authors laboratory showing that serial order perceptual skills emerge at the same time and improve rapidly. Consistent with a multisensory redundancy view of perception, when serial order perceptual abilities first emerge in infancy, they depend critically on the redundant specification of sequences in both the auditory and visual modalities. The findings suggest that infants ability to perceive the surface serial order characteristics of sequentially organized events provides the necessary antecedents to the development of more complex serial order skills that ultimately enable us to extract meanings from sequentially organized events and perform complex sequential actions.Edited by: Marie-Hélène Giard and Mark Wallace     

Acquiring new spatial intuitions: learning to reason about rotations

There are certain simple rotations of objects that most people cannot reason about accurately. Reliable gaps in the understanding of a fundamental physical domain raise the question of how learning to reason in that domain might proceed. Using virtual reality techniques, this project investigated the nature of learning to reason across the domain of simple rotations. Learning consisted of the acquisition of spatial intuitions: there was encoding of useful spatiotemporal information in specific problem types and a gradual accumulation of this understanding across the domain. This pattern of learning through the accumulation of intuitions is especially interesting for rotational motion, in which an elegant domain-wide kinematics is available to support insightful learning. Individual ability to reason about rotations correlated highly with mastery motivation, skill in fluid reasoning, and skill in reasoning about spatial transformations. Thus, general cognitive advantages aided the understanding of individual rotations without guaranteeing immediate generalization across the domain.     

A comparison of masking by visual and transcranial magnetic stimulation: implications for the study of conscious and unconscious visual processing

Visual stimuli as well as transcranial magnetic stimulation (TMS) can be used: (1) to suppress the visibility of a target and (2) to recover the visibility of a target that has been suppressed by another mask. Both types of stimulation thus provide useful methods for studying the microgenesis of object perception. We first review evidence of similarities between the processes by which a TMS mask and a visual mask can either suppress the visibility of targets or recover such suppressed visibility. However, we then also point out a significant difference that has important implications for the study of the time course of unconscious and conscious visual information processing and for theoretical accounts of the processes involved. We present evidence and arguments showing: (a) that visual masking techniques, by revealing more detailed aspects of target masking and target recovery, support a theoretical approach to visual masking and visual perception that must take into account activities in two separate neural channels or processing streams and, as a corollary, (b) that at the current stage of methodological sophistication visual masks, by acting in more highly specifiable ways on these pathways, provide information about the microgenesis of form perception not available with TMS masks.     

How owls structure visual information

Recent studies on perceptual organization in humans claim that the ability to represent a visual scene as a set of coherent surfaces is of central importance for visual cognition. We examined whether this surface representation hypothesis generalizes to a non-mammalian species, the barn owl (Tyto alba). Discrimination transfer combined with random-dot stimuli provided the appropriate means for a series of two behavioural experiments with the specific aims of (1) obtaining psychophysical measurements of figure–ground segmentation in the owl, and (2) determining the nature of the information involved. In experiment 1, two owls were trained to indicate the presence or absence of a central planar surface (figure) among a larger region of random dots (ground) based on differences in texture. Without additional training, the owls could make the same discrimination when figure and ground had reversed luminance, or were camouflaged by the use of uniformly textured random-dot stereograms. In the latter case, the figure stands out in depth from the ground when positional differences of the figure in two retinal images are combined (binocular disparity). In experiment 2, two new owls were trained to distinguish three-dimensional objects from holes using random-dot kinematograms. These birds could make the same discrimination when information on surface segmentation was unexpectedly switched from relative motion to half-occlusion. In the latter case, stereograms were used that provide the impression of stratified surfaces to humans by giving unpairable image features to the eyes. The ability to use image features such as texture, binocular disparity, relative motion, and half-occlusion interchangeably to determine figure–ground relationships suggests that in owls, as in humans, the structuring of the visual scene critically depends on how indirect image information (depth order, occlusion contours) is allocated between different surfaces. Electronic Publication     

Somatovisceral interactions in visceral perception: Abdominal masking of colonic stimuli

Clinical and experimental evidence on referred pain and spinal-afferent convergence demonstrates a close relationship between visceral and somatosensory perception, which is important for current models of symptom perception and central body representation. The study uses a psychophysical approach to quantify these interactions at the perceptual level, taking into account problems of comparable intermodal scaling and the role of awareness. An experiment on somatosensory masking of distension stimuli in the colon is reported in which a multiple staircase method of forced choice discrimination with concurrent sensation ratings was employed. Results showed perceptual masking of visceral by abdominal stimuli but not vice versa. The masking effect was not enhanced by intratomal placement of the abdominal stimulus in the lower left quadrant. This contradicts the spinal sensory convergence model and points to perceptual interactions at higher brain levels. Loglinear analysis of relations between discrimination and subjective sensation revealed qualitative differences of somatovisceral perception at the preconscious as compared to the conscious level. This argues for a two-process model of integrative body perception.     

感知负载对干扰效应和负启动效应的影响

保持刺激图形恒定,用改变任务难度的方法操纵负载的高低,研究了负载的变化对干扰效应及负启动效应的影响。实验结果显示在零负载时出现干扰效应,而高、低负载时干扰效应消失;同时在低、零负载时出现负启动效应,在高负载时负启动反转为正启动。这些结果说明负载的变化对干扰子的状态有明显的作用,但正启动效应的出现显示高负载并不能完全排除对干扰子的加工。     

Determination of visual figure and ground in dynamically deforming shapes

Figure/ground assignment - determining which part of the visual image is foreground and which background - is a critical step in early visual analysis, upon which much later processing depends. Previous research on the assignment of figure and ground to opposing sides of a contour has almost exclusively involved static geometric factors - such as convexity, symmetry, and size - in non-moving images. Here, we introduce a new class of cue to figural assignment based on the motion of dynamically deforming contours. Subjects viewing an animated, deforming shape tended to assign figure and ground so that articulating curvature extrema - i.e., "hinging" vertices - had negative (concave) contour curvature. This articulating-concavity bias is present when all known static cues to figure/ground are absent or neutral in each of the individual frames of the animation, and even seems to override a number of well-known static cues when they are in opposition to the motion cue. We propose that the phenomenon reflects the visual system's inbuilt expectations about the way shapes will deform - specifically, that deformations tend to involve rigid parts articulating at concavities.     

Ageing effects on the attention demands of walking

Attention demands of walking were determined in six male and six female young adults (mean 26.3 yr) and 12 gender-matched healthy, active older adults (mean 71.1 yr) using a dual task procedure with a reaction time (RT) secondary task. In three conditions an auditory stimulus, a visual stimulus and both stimuli (auditory/visual) were presented. Relative to no-walking baselines, increased RT was found in all conditions revealing an attentional cost of normal walking. When participants traversed the laboratory walkway and also positioned one of their feet within a target area on the ground, attention demands were greater than in unconstrained walking. In the targeting task, RTs to the visual stimulus were longer than for the auditory stimulus due to the interference associated with viewing both the stimulus monitor and the foot-target. Older participants' RTs in the visual and auditory/visual conditions, but not in the auditory condition, were significantly longer than for the young group in both walking tasks but RTs for young and older adults were not different in no-walking baseline trials. Inspection of mean RT functions at time intervals following gait initiation (0-3000 ms from the first step) suggested a fluctuating attentional cost of walking with increased demands associated with contingencies requiring step length regulation. The findings have applied significance in demonstrating the possibility of increased falls and pedestrian accident risk in older individuals in dual task situations such as road crossing.     

Perceptual constraints and the learnability of simple grammars

Cognitive processes are often attributed to statistical or symbolic general-purpose mechanisms. Here we show that some spontaneous generalizations are driven by specialized, highly constrained symbolic operations. We explore how two types of artificial grammars are acquired, one based on repetitions and the other on characteristic relations between tones ("ordinal" grammars). Whereas participants readily acquire repetition-based grammars, displaying early electrophysiological responses to grammar violations, they perform poorly with ordinal grammars, displaying no such electrophysiological responses. This outcome is problematic for both general symbolic and statistical models, which predict that both types of grammars should be processed equally easily. This suggests that some simple grammars are acquired using perceptual primitives rather than general-purpose mechanisms; such primitives may be elements of a "toolbox" of specialized computational heuristics, which may ultimately allow constructing a psychological theory of symbol manipulation.