The present study examined whether younger observers (kindergartners, second graders, and fourth graders) could extract relative weight information from collisions and also lifting events, and if they could judge whether collisions were natural (i. e., momentum conserving) or anomalous (non-momentum conserving). 20 children at each age and 20 adults viewed videotapes of 8 collisions (4 natural, 4 anomalous) and 6 sequences of lifting events. Observers also viewed sequences of static images taken from these events. Observers at all grade levels were able to reliably judge relative weight in both collisions and lifting events, and could differentiate between natural and anomalous collisions. Performance was much poorer when static sequences of the events were viewed, especially for the young children. A consistent age trend was noted across tasks: adults performed better than second and fourth graders who, in turn, performed better than kindergartners. In addition, there was evidence that younger children were differentially aided when the kinematics of the event made the kinetics more pronounced.

Two experiments assessed infant sensitivity to figural coherence in point-light displays moving as if attached to the major joints of a walking person. Experiment 1 tested whether 3- and 5-month-old infants could discriminate between upright and inverted versions of the walker in both moving and static displays. Using an infant-control habituation paradigm, it was found that both ages discriminated the moving but not the static displays. Experiment 2 was designed to clarify whether or not structural invariants were extracted from these displays. The results revealed that (1) moving point-light displays with equivalent motions but different topographic relations were discriminated while (2) static versions were not, and (3) arrays that varied in the amount of motion present in different portions of the display were also not discriminated. These results are interpreted as indicating that young infants are sensitive to figural coherence in displays of biomechanical motion.

Passengers in moving vehicles often see an interesting phenomenon when they fixate one of several objects that are at different distances. Looking sideways out the window, they may notice that all objects closer than the fixated object appear to move in a direction opposite to their movement, whereas all objects farther than the fixated object appear to move in the direction in which they are traveling. You can see similar apparent motions by holding your index fingers at different distances while swinging your head back and forth. When you look at the far finger, the near one appears to move against the direction of head movements; when you look at the near finger, the far one appears to move with the direction of head movement. Theterm "motion parallax" is often used in referring to these and other apparent motions that are concomitant with lateral head movements (e.g., Coren, Porac, & Ward, 1979; Gibson, Gibson, Smith, & Flock, 1959; Shebilske & Proffitt, 1981). Gogel, however, prefers the term "apparent concomitant motion." This paper will adopt Gogel's term to avoid clouding issues in an ongoing debate that contends issues much deeper than terminology.

Two sources of visual information that likely could be employed by the perceptual system in locating the centers of bounded shapes—boundary configuration and luminance distribution—have been perfectly confounded in every study thus far aimed at investigating perceived centters. Observers, using either a revolving or stationary x-y plotter, made judgments on the location of centers within either revolving or stationary shapes of both uniform and varied luminance distributions. Results indicate that the location of perceived centers depended predominantly upon boundary contour and was affected by the distribution of luminance within these edges to a much lesser degree.

To achieve a standardization measure, we relate common statistical definitions to related mathematical descriptors of shapes. In particular, we relate the descriptors of a bivariate continuous density function to the moment descriptors that have previously been used in visual pattern recognition and discrimination research (cf. Alt, 1962; Hu, 1962; Zusne, 1970).