Portal de Periódicos da CAPES

Models of stimulus uncertainty in motion perception.

1980; American Psychological Association; Volume: 87; Issue: 5 Linguagem: Inglês

10.1037/0033-295x.87.5.435

1939-1471

Karlene Ball, Robert Sekuler,

Visual perception and processing mechanisms

A model is proposed to account for the loss in visibility of moving targets that occurs when an observer is uncertain about the target's direction of motion.The model's key features are an array of directionally selective visual mechanisms and a rule governing the mechanisms from which an observer will derive sensory data.In response to uncertainty about two possible directions of motion, the observer is assumed to use a mechanism whose peak sensitivity is to a direction midway between the two possible directions.Seven experiments, using both reaction time and forced-choice data, demonstrate the predictive advantages of this midway model over competing single-band and multiple-band models.Additionally, the experiments reveal several new properties of human motion perception: (a) Direction and velocity information have orthogonal representations in the visual system; (b) although motion sensitivity does not vary with direction, the precision with which small changes in direction can be recognized does, reflecting differential breadth of tuning for directionally selective mechanisms sensitive to various directions; and (c) motion-analyzing mechanisms are broadly tuned for direction as well as speed.Human psychophysics provides extensive evidence for the existence of visual mechanisms tuned to different directions of motion.Converging on this point are data from a variety of paradigms including selective adaptation (Sekuler & Ganz, 1963), subthreshold summation (Levinson & Sekuler, 1975), and aftereffects (Keck, Palella, & Pantle, 1976).In addition, we recently used a masking procedure to define the direction sensitivity profiles of these mechanisms (Ball & Sekuler, 1979).In general, these studies tell us how much information is potentially available in motion-sensitive visual elements under ideal conditions.But they tell us little about the use to which that information can be put under nonideal conditions outside the laboratory.