Developmental differences in shape processing

Considerable evidence indicates that shape similarity plays a major role in object recognition, identification and categorization. However, little is known about shape processing and its development. Across four experiments, we addressed two related questions. First, what makes objects similar in shape? Second, how does the processing of shape similarity develop? We specifically asked whether children and adults determine shape similarity by using categories (e.g., straight vs. curved), as proposed by Biederman (1987), or whether they treat all shape variability uniformly, as proposed by Ullman (1998). Findings from Experiments 1 and 2 suggest that adults and 7-year-olds generally engage in a process in which they impose categories on shape variation and judge objects that fall within those categories as being similar in shape. Four-year-olds are far less likely to engage in such a process. Experiments 3 and 4 address whether 4-year-olds are more likely to treat shape similarity categorically (as older children and adults do) when the objects are given familiar names, functions, and internal properties. Naming did lead to more advanced treatment of shape similarity in some cases. Overall, these findings provide evidence of developmental differences in shape processing and suggest that knowledge of abstract properties of objects may affect the calculation of shape similarity.     

In any way,shape, or form? Toddlers’ understanding of shapes

Using the intermodal preferential looking paradigm, two-year-old children’s ability to discriminate valid (typical and atypical) squares, rectangles, triangles, and circles from invalid distractors was examined. The cognitive and environmental factors that might predict this ability were also investigated. Two-year-old children (N = 33) were able to discriminate squares, triangles, and circles, but not rectangles. No significant cognitive or environmental predictors of this ability were found. The results suggest that the ability to shape discriminate at age two is under considerable development and that other factors may be responsible for children’s ability to discriminate shapes.     

基于空间方位信息的构型对视觉工作记忆绩效的影响

通过考察构成视觉客体构型的两种因素在视觉工作记忆任务中的影响, 探讨了构型对视觉工作记忆绩效的作用机制。采用变化觉察实验范式, 在构型朝向不变和旋转两种条件下, 系统地控制构型中的客体相对方位和整体几何形态两种因素的变化, 考察其对视觉工作记忆绩效的影响。实验结果显示, 无论构型朝向不变还是旋转, 只要客体相对方位保持一致, 工作记忆绩效就可以维持较高水平, 而几何形态没有表现出显著作用。上述发现提示构型客体相对方位是构型影响视觉工作记忆绩效的主要因素。     

Attentional processing of location and color cues during driving

Studies have shown that prior information concerning the spatial location of a subsequent target facilitates the selection of that target for further visual processing in three-dimensional (3-D) space. Using Posner's cuing paradigm, our work examined the reaction time of drivers when cue duration and peripheral environment luminance was changed, and explored the effect color and location on reaction time. Experiment 1 showed that reaction time was not affected by cue duration, and that shifts of attention operated more efficiently for cue location validity. Experiment 2 showed that there was no main effect of background luminance on reaction time. Experiment 3 showed that location produces a greater effect than color.     

Confidence regions for multidimensional scaling analysis

Techniques are developed for surrounding each of the points in a multidimensional scaling solution with a region which will contain the population point with some level of confidence. Bayesian credibility regions are also discussed. A general theorem is proven which describes the asymptotic distribution of maximum likelihood estimates subject to identifiability constraints. This theorem is applied to a number of models to display asymptotic variance-covariance matrices for coordinate estimates under different rotational constraints. A technique is described for displaying Bayesian conditional credibility regions for any sample size.The research reported here was supported by grant number APA 320 to the author by the National Research Council of Canada.     

Segmentation of object outlines into parts: a large-scale integrative study

In this study, a large number of observers (N=201) were asked to segment a collection of outlines derived from line drawings of everyday objects (N=88). This data set was then used as a benchmark to evaluate current models of object segmentation. All of the previously proposed rules of segmentation were found supported in our results. For example, minima of curvature (i.e. locations along the contour where negative curvature takes an extreme value) were often used as segmentation points. The second point of a pair connected by a segmentation line often depended on more global shape characteristics such as proximity, collinearity, symmetry, and elongation. Based on these results, a framework is presented in which all of the previously proposed (and now empirically validated) segmentation rules or rules for part formation are integrated.     

网格对工作记忆中视觉客体空间位置编码的影响

为探究网格在工作记忆中对视觉客体位置编码的影响,本研究采用n-back范式,通过客体位置的确定性和网格出现的不同认知加工阶段,探索了网格线在空间工作记忆视觉客体位置记忆中的作用机制.实验1的结果表明,被试将依据客体的位置确定性强弱来选择类别编码或坐标编码.实验2的结果显示,网格在识记阶段可能有利于位置记忆,而在提取阶段可能有干扰作用.     

“Where is the sun” for hemi-neglect patients?

Human observers use prior constraints to disambiguate a scene; in particular, light is preferentially seen as coming from above but also slightly from the left. One explanation of this lateral bias could be a cerebral hemispheric difference. The aim of the present study was to determine the preferred light source position for neglect patients. For this purpose, we used the ambiguous shaded “Polo Mint” stimulus, a ring divided into eight equal sectors. All sectors but one were the same shape, convex or concave, as determined by the light source position. Participants had to report the side (left or right) of the odd sector or, in a separate experiment, to report its shape (convex or concave). Eight patients with spatial neglect (left neglect N = 7, right neglect N = 1) after a right or left temporo-parietal or thalamic lesion and 14 control participants ran the experiment. Left neglect patients showed a significantly different light bias from the bias observed for controls and for the right neglect patient (i.e., a reduction of the left bias or a right bias rather than a left bias). We conclude that some disabilities presented by patients with spatial neglect may be due to difficulties processing information that is not present in the visual field or imagined in the representational scene.     

Fifteen-month-old infants attend to shape over other perceptual properties in an induction task

This study examined whether infants privilege shape over other perceptual properties when making inferences about the shared properties of novel objects. Forty-six 15-month-olds were presented with novel target objects that possessed a nonobvious property, followed by test objects that varied in shape, color, or texture relative to the target. Infants generalized the nonobvious property to test objects that were highly similar in shape, but not to objects that shared the same color or texture. These results demonstrate that infants’ attention to shape is not specific to lexical contexts and is present at the early stages of productive language development. The implications of these findings for debates about children's shape bias, in particular, and the nature of infants’ categories more generally, are discussed.