Symmetry and similarity effects in the comparison of visual patterns

Abstract

and CARLO UMILTAUniversity 0/Parma, Parma, Italy Models to explain same-different RT disparity have variously emphasized encoding or comparison processes. Of the latter, a dual-process holistic-analytic model that bears a similarity to a putative distinction between hemispheric processes has been proposed. Here two experiments test the models by employing simultaneous and successive matching whilevarying letter similarity, symmetry, and visual field of presentation. Same-different disparity is found regardless of delay, although it can be eliminated with appropriate similarity and symmetry manipulations. While visual field interacts with the same-different factor, it fails to do so in a manner consistent with the proposed hemispheric dichotomy. These and other results argue against encoding models of letter matching, and support a revised visual comparison model that incorporates dual processing and response criterion elements. However, the role of lateralized processes remains unclear.578

Visual laterality for letter comparison: Effects of stimulus factors, response factors, and metacontrol

“…With respect to the LVF/RH and RVF/LH trials, it can be seen that for RVF/LH trials, reaction times are faster to same pairs than to different pairs (p < .01), whereas there is no significant effect of stimulus type for LVF/RH trials. As a result, when analysis is restricted to the unilateral trials, Bagnara et al, 1983;Egeth & Epstein, 1972). Although the interpretation of this effect must remain somewhat speculative, it is consistent with a recent report that the left hemisphere is more sensitive than the right hemisphere is to the common features of two stimuli (Frost & Gati, 1989).…”

“…This effect is referred to as the fast-same effect, and its interpretation is a matter of considerable speculation (e.g., Farell, 1985Farell, , 1988 each trial, it is often the case that the fast-same effect is restricted to RVF/LH trials (e.g., see Bagnara, Boles, Simion, & Umilta, 1983;Egeth & Epstein, 1972), producing a same/different x visual field interaction. As Bagnara et al argue, this result suggests that the left and right hemispheres perform the letter-comparison task in qualitatively different ways (see Bagnara et al, for consideration of what these different modes of processing might be).…”

Hemispheric mediation of same-different judgments: A reply

“…Of the six major criticisms raised by Sergent (1984) against the paper by Bagnara et al (1983), we view notre as having a great practical import. To recap, uncontrolled viewing distance, while perhaps an undesirable feature of the methodology, neither precluded finding visual field effects nor introduced insurmountable error variance into the results.…”

“…Although impressed by the prescience of the prediction of the interaction, we are skeptical about the While literature can be cited for both sides of the argument relating to variation in eccentricity (see Bagnara et al, 1983, andSergent, 1984, for references) and stimulus size (see Sergent, 1984, and Boles, in press, for references and experimental results), the issue seems to come down to whether the lack of control over distance introduced sufficient error variance to rule out significant field differences. This is an empirical question answerable with the obtained data.…”

“…Figure 1. Visual field X match X response hand interaction in Experiment 1 of Bagnara et al, (1983).…”