Absence of relational determination in the rod-and-frame effect

Abstract

. InRelational features between a rod and frame that might facilitate an angle-detection process were manipulated in two ways: first, by varying rod lengths with retinal eccentricities of 3.8 0 ,7.5 0 , and 14.8 0 in a frame with inner dimensions of 35.3°x 35.3°, and second, by eliminating the sides, leaving only the corners of the frame. The converse case, in which corners were eliminated but sides left intact, represented the control condition. In neither case did the opportunity to use relational features enhance the rod-and-frame effect (RFE). In a frame with inner dimensions of 52.5°x 52.5 0 , when line length had an eccentricity of about 25 0, reducing it to 3 0 did significantly reduce the RFE, but only for those who scored in the upper 50% as measured on the full-frame RFE. An explanation is proposed based upon visual-vestibular interactions between receptive fields in peripheral retina and orientation detectors in the vestibular nucleus.

The Ponzo illusion and the perception of orientation

“…The evidence for this assertion is a comprehensive series of experiments by Ebenholtz and his colleagues, demonstrating that the magnitude of the rod-and-frame effect increases as the stimulus gets retinally larger (e.g., Ebenholtz, 1977Ebenholtz, , 1985Ebenholtz & Callan, 1980). As the stimulus gets larger, the frame falls more in the periphery.…”

The gap between rod and frame influences the rod-and-frame effect with small and large inducing displays

“…Furthermore, Coren and Hoy's (1986) observation that a gap in the range of 1°-2°may be critical in producing orientation contrast effects suggests a tentative interpretation of the results of Ebenholtz's (1985) Experiment 3, alternative to what he proposed. In fact, in Ebenholtz's Experiment 3, the spatial separation between the rod ends and the frame was approximately 1.5°in the case of the large rod and a significant difference between rods of different lengths was observed.…”

“…In commenting upon Ebenholtz's (1985) study, Coren and Hoy (1986) noted that the absence of a gap effect had been obtained using spatial separations of more than 3°o f visual angle between the rod and the frame. On the contrary, orientation contrast effects are known to be maximal within the range of 1°_2° (Carpenter & Blakemore, 1973).…”

“…In particular, Ebenholtz (1985) referred to Koffka's (1935) idea of relational determination according to which "the apparent orientation of the line is largely predicated on the specific angle the line makes relative to a frame edge" (p. 303). Ebenholtz reasoned that, if this theory was correct, the manipulation of the ease with which the angular relation of line to frame can be detected should produce direct effects on the size of the illusory effect.…”

Spatial context affects the Poggendorff illusion

“…For example, a simple tilted frame greatly affects an observer's perception of true vertical (Asch & Witkin, 1948;Beh, Wenderoth, & Purcell, 1971;Ebenholtz, 1977Ebenholtz, , 1985aEbenholtz, , 1985bEbenholtz, , 1985cEbenholtz & Utrie, 1982Wenderoth, 1974;Witkin & Asch, 1948). It is conceivable that a similar frame may affect an observer's perception of collinearity in the Poggendorff illusion.…”