Movement, Psychology of

Visual motion can be conveyed by a variety of information sources in the environment, and those types of information may be detected at various levels by different motion-perceiving mechanisms in the visual system. High-level visual information has been demonstrated to have 3rd order, or salience-based properties (Lu & Sperling, 1995). The perceptual system they describe that computes motion from these types of information shares several characteristics with Hock and colleagues' counterchange detection system, notably flexibility with respect to types of input from which motion can be computed, which comes at the cost of diminished processing speed. The mechanism of counterchange detection is well suited to processing visual features often present in environmental scenes, e.g., objects and surfaces, and may be a mechanism of 3rd order motion. Consistent with reported properties of 3rd order motion, the current experiments tested count erchange-, luminance-, and color-based motion stimuli with 3 objectives: to identify whether the 3 systems framework generalizes beyond the stimulus type with which it was defined, to test whether counterchange shares similarities with the 3rd order system with respect to dichoptic integration, and perception of isoluminant color-based motion, and to test subjectively objectless sources of motion-defining information (spreading luminance and hue) to see if they display properties of the 1st order system derived from sine wave gratings. Results indicate that counterchange-based stimuli displayed predicted properties of dichoptic integration, and perception at isoluminance, but putative 1st order (spreading) stimuli also displayed these properties. This may suggest that object-like surfaces, even when not directly the source of motion information, can contribute to computation of motion. Further, these results highlight the difficulty of generalizing from one theoretical framework to another, and specifically, of psychophysically testing high-level information while isolating contributions from low level information upon which high level visual stimuli are built.