Dichoptic and dichotic micropattern discrimination

Abstract

Ss compared two rapidly successive, brief, discriminably different stimulus elements, called a micropattern, with a second micropattern composed of the same two stimulus elements presented in reverse temporal order. Discriminations could be made between two such micropatterns in the monaural (monocular) as well as in the dichotic (dichoptic) modes of presentation. Discrimination between micropatterns was based on the perceptual dominance of the temporally trailing stimulus element in both modalities and in both modes of presentation. While monaural (monocular) micropattern discrimination is significantly superior to dichotic (dichoptic) discrimination, the existence of dichotic (dichoptic) discrimination demonstrates that no essential peripheral process is required for micropattern discrimination.Recent experiments in this laboratory in the visual, auditory, and vibratory modalities (Efron, 1973) have been concerned with the discrimination of brief, complex stimuli differing only in their fine temporal structure. In these experiments, Ss compared two consecutive, brief, discriminably different stimulus elements, called a micropattern, with a second micropattern composed of the same two stimulus elements presented in the reverse temporal order. Ss readily discriminated between micropattems having reversed temporal order of stimulus elements in all three modalities, even when the temporal asynchrony between the stimulus elements was so far below the threshold for making temporal order judgments that each micropattern was experienced as a unitary perceptual event. The discriminations were based on the perceptual dominance of the second or trailing stimulus element. Additional studies revealed that the trailing stimulus element phenomenally dominated the perception of each micropattem by virtue of a retroactive degradation of the perceptual experience of the leading element. This perceptual degradation of the leading stimulus element by the trailing element did not have the properties of retroactive masking.In all the previous experiments, the two stimulus elements of each micropattem were presented to the same eye, ear, or skin location-an experimental paradigm which did not permit any analysis of the neuroanatomical locus of the retroactive interaction. In the experiments to be described here (in the auditory and visual modalities), the same micropattems were presented dichotically (dichoptically)-one stimulus element of the micropattern to each ear (eye). If there is an essential peripheral process involved in micropattem discrimination in the basilar membrane or in the retina, the phenomenon of perceptual dominance of the trailing stimulus element would not be expected in such dichotic (dichoptic) presentations. The purpose of the present experiments was to determine (l) whether dichotic and *From the VA Hospital and the Department of Neurology, University of California, School of Medicine, Davis, California. 383 dichoptic micropattern discriminations are possible, (2) whether the discriminations (if possible) a...

Feature processing during high-rate auditory selective attention

“…Although feature integration has been studied largely in the visual modality, certain similar effects-for example, conjunction errors-have been observed for auditory signals (Treisman, 1988). For example, subjects may erroneously combine the frequency of one tone with the location of another (Yund & Efron, 1974).…”

Experiments on the Fehrer–Raab effect and the ‘Weather Station Model’ of visual backward masking

“…For the sake of comparison, these values are depicted, too especially if the two stimuli are spatially close to each other. It allows discrimination even with SOAs of a few ms (Efron, 1973;Yund & Efron, 1974). In these cases a temporal feature of the stimuli is represented, but not as a temporal aspect of the phenomenal representation but as a spatial or qualitative property.…”

High temporal precision for perceiving event offsets

“…In sum, studies exploiting motion cues to aid temporal order discriminations yielded asynchrony thresholds between 2 and 5 ms (Sweet, 1953; Westheimer & McKee, 1977; Wehrhahn & Rapf, 1992). Remarkably, for spatially overlapping color targets, detection of temporal order asynchronies of less than 1 ms has been demonstrated (Yund & Efron, 1974). …”

“…As many of the aforementioned papers readily admit, these measurements are confounded by non-temporal cues, such as apparent motion caused by asynchronous stimulus onsets (e.g., Westheimer & McKee, 1977) and visual persistence of the trailing target (e.g., Yund & Efron, 1974). To directly address these confounds, Zanker & Harris (2002) investigated the temporal precision of vision in a task that is uncontaminated by non-temporal information.…”

“…The authors do not offer an explanation of this discrepancy, indicating that future work is necessary. Yund and Efron (1974) examined temporal order discriminations for both onset and offset asynchronies and found that offset discriminations were more precise, with offset asynchrony discrimination thresholds less than 0.5 ms. This remarkable performance is most likely due to the visual persistence of the target that offset last – i.e., it likely does not reflect the true temporal precision of vision (Zanker & Harris, 2002).…”