Visual Perception of Biomechanical Characteristics of Walking, Jumping, and Landing

Visual perception of biological systems is one important aspect which has been considered by researchers in understanding human motion. The term «biological motion» was used by Johansson (1971, 1973) to distinguish human movement patterns from the motion of rigid inanimate objects previously utilized in visual motion perception. The emphasis, however, has been on the need for distinguishing three types of motion to describe perceived kinematic relations: the relative motion of elements to each other in the configuration, the common motion of the whole configuration relative to the observer, and the absolute motion of each element in dynamic display [Cutting and Proffitt (1982)]. Based on data collected using a video-recorder, reflective tape and high powered light for producingpoint-light displays, Cutting and Proffitt (1982) concluded that relative motion is automatically minimized by the visual system. Moreover, Johansson (1971, 1973) showed that all movement pattern of walking and running can be visually identified by observers without seeing the total picture. Using a similar technique, observers were able to visually recognize gender and friends by their walking patterns (Cutting and Kozlowzki, 1977; Cutting, 1978), ones' own identity (Beardsworth and Buckner, 1981), the weight of lifted objects (Runeson and Frykholm, 1983), and to the extent that evaluation of technical skill execution was sucessfully judged (Scully, 1986). Based on the principle that relative motion is automatically minimized by the visual system, Johansson (1973), concluded that previous learning of motion patterns do not determine the perception of walking. An important factor, however, is a highly mechanical, automatic type of visual data treatment. In addition, Runeson and Frykholm (1981) stated that the dynamic variable of the event (weight of the box), is well specified in the kinematic pattern and hence the visual system is efficient in picking up such information. Identifying cues by visual information may not be sufficient, however, to distinguish discrete skills (ie., jumping and landing) and/or continuous skills (ie., walking), especially, if the direction of the movement is reversed and if the total picture is seen as an absolute motion which includes the relative and common motion (Cutting and Proffitt, 1982). Therefore, this study was conducted to test the hypotheses that experience and familiarity are important factors in visual perception of kinematic patterns and that kinetics cannot be determined effectively by observation of kinematics. The purpose of this study is to determine: (1) the ability to visually perceive differences between a continuous skill (walking forward vs. backwards): (2) a discrete skill (jumping vs. landing); (3) the actual kinetic differences in the movement; and (4) whether individuals can distinguish between movement patterns, despite the kinetic differences, while the true pattern is reversed

The very same thing: Extending the object token concept to incorporate causal constraints on individual identity

The contributions of feature recognition, object categorization, and recollection of episodic memories to the re-identification of a perceived object as the very same thing encountered in a previous perceptual episode are well understood in terms of both cognitive-behavioral phenomenology and neurofunctional implementation. Human beings do not, however, rely solely on features and context to re-identify individuals; in the presence of featural change and similarly-featured distractors, people routinely employ causal constraints to establish object identities. Based on available cognitive and neurofunctional data, the standard object-token based model of individual re-identification is extended to incorporate the construction of unobserved and hence fictive causal histories (FCHs) of observed objects by the pre-motor action planning system. Cognitive-behavioral and implementation-level predictions of this extended model and methods for testing them are outlined. It is suggested that functional deficits in the construction of FCHs are associated with clinical outcomes in both Autism Spectrum Disorders and later-stage stage Alzheimer's disease.\u

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Perceptual Kinds as Supervening Sortals

It seems intuitive that in situations of perceptual recognition additional properties are represented. While much has been written about the significance of such properties for perceptual phenomenology, it is still unclear (a) what is the relation between recognition-based properties and lower-level perceptual properties, and (b) whether it is justified to classify them as kind-properties. Relying on results in cognitive psychology, I argue that recognition-based properties (I) are irreducible, high-level properties, (II) are kind properties by virtue of being sortal properties, but (III) they supervene on lower-level properties and so are unlikely to be natural kind properties