Learned prediction affects body perception

Learning to recognize objects appears to depend critically on extended observation of appearance over time. Specifically, temporal association between dissimilar views of an object has been proposed as a tool for learning invariant representations for recognition. We examined heretofore untested aspects of the temporal association hypothesis using a familiar dynamic object, the human body. Specifically, we examined the role of appearance prediction (temporal asymmetry) in temporal association. In our task, observers performed a change detection task using upright and inverted images of a walking body either with or without previous exposure to a motion stimulus depicting an upright walker. Observers who were exposed to the dynamic stimulus were further divided into two groups dependent on whether the observed motion depicted forward or backward walking. We find that the effect of the motion stimulus on sensitivity is highly dependent on whether the observed motion is consistent with past experience.     

Learning influences the encoding of static and dynamic faces and their recognition across different spatial frequencies

Studies on face recognition have shown that observers are faster and more accurate at recognizing faces learned from dynamic sequences than those learned from static snapshots. Here, we investigated whether different learning procedures mediate the advantage for dynamic faces across different spatial frequencies. Observers learned two faces—one dynamic and one static—either in depth (Experiment 1) or using a more superficial learning procedure (Experiment 2). They had to search for the target faces in a subsequent visual search task. We used high-spatial frequency (HSF) and low-spatial frequency (LSF) filtered static faces during visual search to investigate whether the behavioural difference is based on encoding of different visual information for dynamically and statically learned faces. Such encoding differences may mediate the recognition of target faces in different spatial frequencies, as HSF may mediate featural face processing whereas LSF mediates configural processing. Our results show that the nature of the learning procedure alters how observers encode dynamic and static faces, and how they recognize those learned faces across different spatial frequencies. That is, these results point to a flexible usage of spatial frequencies tuned to the recognition task.     

The relationship between apparent motion and object files

Object files (OFs) play an important role in theories of mid-level vision. On some influential views, OFs operate and persist only via spatiotemporal continuity. One open question concerns what occurs when direct spatiotemporal continuity is absent: Do OFs move in accordance with any motion correspondence ultimately resolved? Specifically, do OFs accord with apparent motion (AM) correspondences, which arise despite a lack of continuous spatiotemporal stimulation? In Experiment 1, subjects were presented with an AM display consisting of two circles that, across two frames, were seen as moving between two noncontiguous locations. The two objects were primed with two symbols and were then moved in a single step; a third symbol appeared, and could either match the symbol from the closer or the further object. We found a robust object specific preview benefit (OSPB) for the shorter path, in other words, the path along which AM was perceived. In order to control for the possibility that priming occurs at any nearby object, in Experiment 2, the original two objects never disappeared, but two new objects appeared in the would-be AM locations. No AM was perceived, and no OSPB obtained. In the third experiment the OSPB effect persisted even when motion along the shorter path included an unlikely featural transformation (circles turning into squares). In Experiment 4, which was nearly identical to Experiment 2, no OSPB obtained despite unique featural matches between the initial and new objects, seemingly because no AM was perceived. In Experiment 5, we failed to find an effect of featural priming, even when distance between the objects was equated. Finally, we extended the OSPB effect to two additional kinds of AM—line motion (Experiment 6) and phi motion (Experiment 7), supplying strong evidence that AM correspondences and OF correspondences are controlled by the same basic rules.     

Neural Correlates of Age-related Reduction in Visual Motion Priming

ABSTRACT

Previously we reported that priming of visual motion perception is reduced in older adults compared to younger adults (Jiang, Greenwood, & Parasuraman, 1999 Jiang, Y., Greenwood, P. and Parasuraman, R. 1999. Age-related reduction in 3-D motion priming. Psychology and Aging, 14(4): 619–626.  [Google Scholar], Psychology and Aging, 14(4), 619; Jiang, Luo, & Parasuraman, 2002b Jiang, Y., Luo, Y. J. and Parasuraman, R. 2002b. Two-dimensional visual motion priming is reduced in older adults. Neuropsychology, 16(2): 140–145.  [Google Scholar], Neuropsychology, 16(2), 140). To examine the neural mechanisms underlying this age-related effect, event-related brain potentials (ERPs) were recorded during perceptual judgments of motion directions by younger and older adults in two experiments. When judging single-step motion, both younger and older adults evoked significantly larger ERP late positive component (LPC) responses to unambiguous motion compared to LPC responses elicited by ambiguous motion. In contrast, compared to the younger adults, the older adults evoked comparable but delayed ERP responses to single motion steps. In the second experiment the younger and older groups judged the directions of two successive motion-steps (either motion priming or motion reversals). Under short (200–400 ms) stimulus onset asynchrony (SOA), the difference between the ERP responses to priming and reversal conditions was significantly larger for the younger than for the older adults. This study provides the first electrophysiological evidence that brain aging leads to delayed processing of single motion direction and visual motion priming as early as 100 ms in the early visual cortex. Age-related changes in strength and temporal characteristics of neural responses in temporal-parietal regions were particularly pronounced in older adults when successive motion signals are placed closely in time, within 400 ms.     

Pigeons' discrimination of Michotte's launching effect

We trained four pigeons to discriminate a Michotte launching animation from three other animations using a go/no-go task. The pigeons received food for pecking at one of the animations, but not for pecking at the others. The four animations featured two types of interactions among objects: causal (direct launching) and noncausal (delayed, distal, and distal & delayed). Two pigeons were reinforced for pecking at the causal interaction, but not at the noncausal interactions; two other pigeons were reinforced for pecking at the distal & delayed interaction, but not at the other interactions. Both discriminations proved difficult for the pigeons to master; later tests suggested that the pigeons often learned the discriminations by attending to subtle stimulus properties other than the intended ones.     

Perception of motion affects language processing

Recently developed accounts of language comprehension propose that sentences are understood by constructing a perceptual simulation of the events being described. These simulations involve the re-activation of patterns of brain activation that were formed during the comprehender's interaction with the world. In two experiments we explored the specificity of the processing mechanisms required to construct simulations during language comprehension. Participants listened to (and made judgments on) sentences that described motion in a particular direction (e.g. "The car approached you"). They simultaneously viewed dynamic black-and-white stimuli that produced the perception of movement in the same direction as the action specified in the sentence (i.e. towards you) or in the opposite direction as the action specified in the sentence (i.e. away from you). Responses were faster to sentences presented concurrently with a visual stimulus depicting motion in the opposite direction as the action described in the sentence. This suggests that the processing mechanisms recruited to construct simulations during language comprehension are also used during visual perception, and that these mechanisms can be quite specific.     

儿童运动行距预测能力的发展及影响因素

采用计算机软件控制实验,以三种不同运动速度、四种不同运动行距组合呈现的光点运动为刺激物,每次光点在暴露运动一段行程后进入遮蔽,要求儿童判断光点到达目标位置时按键反应。主要结果表明：（１）儿童运动行距预测能力的发展表现为５─８岁和１２─１９岁两个加速期及８─１２岁一个过渡期的发展模式。但在过渡期内,儿童的预测误差偏向有显著变化;（２）客体运动速度对儿童运动行距预测操作精度有显著影响,慢速下精度较高;（３）客体运动行距、被试性别并不影响儿童的行距预测操作;（４）５岁、１２岁与１９岁儿童多倾向于超前反应。     

An application of the optic sphere theory in discrimination of slant with minimal information

In Johansson and Börjesson (1989), a new theory of visual space perception—the optic sphere theory—was presented in which the hemispheric shape of the retina is utilized for determination of slant of plane surfaces in wide-angle perception. The process of the optic sphere mechanism can be described as the projection of a translating distal line on the optic sphere, and an extrapolation of this projection to a great circle. The determination of the 3-D slant of the distal line is made by identification of points of no change on the great circle during its rotation. The main objective of the present study was to investigate this process as applied to central stimulation of the retina with reduced and minimal information of slant or horizontal orientation. Each stimulus pattern consisted of either two continuous lines or two pairs of dots in motion presented on a computer screen. The pairwise lines and the pairs of dots defined simulated 3-D slants (or horizontal orientations) of different magnitude within each pair, and the subjects' task was to discriminate between these simulated slants. It was shown that the simulations evoke percepts of 3-D slants, and of horizontal orientations, and that it is possible to discriminate between them even from minimal information (pairs of dots). Further, the empirical findings of Börjesson (1994) indicated that longer extrapolations of the projected arc to a point of no change yield less accurate discriminations of slant. We failed to replicate this in Experiment 4, in which case stimulus variables that covaried with extrapolation length were eliminated or minimized. It is suggested that this raises some doubt about discrimination accuracy as dependent on extrapolation length per se. The overall conclusion, however, is that the optic sphere theory represents a possible explanation of, or analogy to, the process utilized by the visual system for determination of the simulated 3-D slants and horizontal orientations in the present study.