Illusions of time and extent when the Müller-Lyer figure moves in an aperture

Abstract

Following informal observations, three experiments confirmed that the Miiller-Lyer illusion occurs when the composite figure consisting of angles-outward and angles-inward components is progressively exposed in a narrow slit, as in the Zollner-Parks demonstrations. The illusion of extent was consistent over subjects and about half that with the figure stationary and moving in full view. The experiments showed also that there is a parallel illusion of time, with one of the two equal extents taking apparently longer than the other to pass the slit. The illusion of extent was enhanced or canceled by manipulating the relative velocities of the two components and, therefore, the time taken by them to pass the slit. It is argued that time of exposure in the slit serves as the reference for extent. The illusions of time and extent are attributed to a perceptual compromise between the time taken by an extent to pass the aperture and that of the component itself to do so. The role of time in perceived extent and its possible involvement in visual scanning are considered.

A quantitative analysis of illusion magnitude predicted by several averaging theories of the Müller-Lyer illusion

“…It also occurs in spatial and temporal visual domains (Day & Duffy, 1988;DeLucia & Hochberg, 1985;Hochberg, 1968) and in the haptic mode (e.g., Over, 1966). The ML illusion is therefore relevant to theories of normal perception and to practical concerns about perceptual accuracy.…”

Apparent depth from progressive exposure of moving shadows: The kinetic depth effect in a narrow aperture

“…They involved binocular observation of parallel projections in a narrow vertical aperture of 2-D and 3-D "skeletal" objects when they were stationary and when they were rotating about their vertical axes. The subjects sat with their eyes 200 cm from a mid-gray opaque screen 100 cm wide and 43 cm high mounted on a table (see Day & Duffy, 1988). A central aperture 2 cm wide extended from the top to the bottom of the screen.…”

Two principles of perception revealed by geometrical illusions

“…That is to say, the M-L illusion occurs even though the moving stimulus figure is never fully visible. Day and Duffy (1988) later noted that when the apparently longer component of the stimulus figure moved past the aperture it appeared to take longer to do so than the apparently shorter but physically equal component. This led them to ask the question: If the apparently longer component is moved quickly past the aperture so that it is visible for a shorter time and the apparently shorter component slowly so that it is visible for a longer time is the M-L illusion cancelled or even reversed?…”