Potential artifact in dichoptic backward masking.

Under some conditions a dark interval in the target eye may be concomitant with presentation of a dichoptic mask. Results show that this monoptic dark interval contributes to the over-all observed dichoptic masking effect.     

Color-selectivity in simultaneous motion contrast

Thirty-two Ss were required to estimate the apparent motion of stationary vertical lines viewed against a background of moving vertical lines when both patterns were seen by the same eye (monoptic conditions) or the center pattern was seen by one eye and the surrounds by the other eye (dichoptic conditions). The stationary lines appeared to be moving from right to left as the surrounds moved left to right. The simultaneous motion contrast found under monoptic conditions was maximal when the center pattern and the surrounds were the same color and was reduced when they differed in color. The surrounds had limited influence on the apparent motion of the center section under dichoptic condition, and the color relationship was no longer important. Related color selectivity has been reported for the motion aftereffect (successive motion contrast), and both sets of data can be attributed to inlaibitory interaction (simultaneous in one case and successive in the other) among neural detectors tuned to wavelength as well as the direction of image motion.     

Loss of wavelength selectivity in contour masking and aftereffect following dichoptic adaptation

Two experiments measured the apparent orientation (aftereffect) and the threshold for detection (masking) of a colored grating viewed by one eye after exposure to a colored grating to the same or the opposite eye (monoptic inspection) or after stimulation of one eye by color and the other eye by contours (dichoptic inspection). Under the monoptic condition, the color relationship between the inspection and test stimuli exerted control over the extent of aftereffect and masking when the two stimuli were viewed with the same eye, but not when they were seen with different eyes. Aftereffect and masking were nonselective to wavelength following dichoptic inspection, irrespective of whether the test stimulus was presented to the color-adapted or to the contour-adapted eye. The results support other claims that visual detectors with chromatic and spatial tuning have monocular specificity.     

The attentional dynamics of masked detection

A dichoptic masking procedure was used to test whether the mask-dependent cuing effects found in luminance detection by P. L. Smith (2000a) were due to integration masking or interruption masking. Attentional cuing enhanced detection sensitivity (d') when stimuli were backwardly masked with either dichoptic or monoptic masks, whereas no cuing effect was found with unmasked stimuli, implying the mask dependencies were due to interruption of stimulus processing in visual cortex by the mask. The effect is predicted by a gated diffusion process model in which masks interrupt stimulus processing and attention controls the flow of information to a sequential-sampling decision mechanism. The model correctly predicts different patterns of performance for detection and discrimination and cuing effects in simple reaction time.     

The locus of masking shape-at-a-slant

Twelve subjects provided shape and orientation judgments for a set of projectively equivalent, variously rotated rectangles under three viewing conditions—monoptic, dichoptic, and binocular—with and without the presence of a pattern mask. In the absence of the mask, partial constancy was exhibited under the first two conditions and near perfect constancy under the binocular condition. Orientation was discriminated. Presence of the mask produced projective shape matching and diminished orientation discrimination. It is argued that the site of masking was postchiasmal, and the results are related to previous work with pattern masking of projectively equivalent ellipses.     

Latency differences in monoptic and dichoptic shape and color decision making

Past research based on the McCollough effect and efficacy of chromatic cues in stereopsis suggests that color information is difficult to process binocularly as compared to form information. This study evaluates this proposition using a reaction time paradigm. Subjects decided whether two simultaneous visual stimuli were the same in shape or color. With presentation to the same eye, color reaction times led shape latencies. Presenting one target to one eye and one to the other slowed color times. Delaying one target by 500 msec yielded dichoptic and monoptic color decisions faster than shape. The results are related to the relationships of color and contrast pathways and possible differences in binocular rivalry.     

Direct measures of short-term visual storage

Two experiments, involving seven conditions, explored the use of direct measures of visual persistence. In each, the subject was asked to judge if an intermittent stimulus appeared perceptually continuous, or whether it completely faded before the next presentation occurred. The first experiment showed that visual persistence was set at approximately 250 msec. for a recycling presentation of a circle in a tachistoscope; in another task employing a moving opaque slit passing back and forth over a circle, persistence times averaged 50 msec. longer. Reducing luminance by 2 log units increased persistence only slightly, though removing the adapting field increased it by over 100 msec. The second experiment, using the repeating circle, varied the duration of the stimulus, and compared monoptic with dichoptic presentations. Visual persistence was found to be independent of stimulus duration over a range of 4 to 200 msec., where all durations were above recognition threshold for the stimulus. Persistence was unaffected whether the stimulus was repeatedly presented in the same eye or alternated between eyes, strongly suggesting that the storage is central. Finally, a re-analysis of Dodwell and Engel's paper on stereopsis suggests that their effects can be adequately explained by visual persistence of the asynchronous stereo pairs, rather than a more complex fusion model. All of these results strongly support the use of visual persistence as a direct measure of short-term visual storage.     

Perceptual masking: Peripheral vs central factors

Perceptual masking was studied under binocular and dichoptic conditions in order to separate peripheral and central interference effects. Under binocular conditions, when the test flash (TF) and the blanking flash (BF) fell on both retinas, both retroactive and proactive masking were demonstrated. Under dichoptic conditions, when the TF fell on one eye and the BF on the other eye, thus eliminating opportunity for intraretinal interference, there was partial retroactive perceptual masking and no proactive masking. These results suggest that binocular proactive masking is due to peripheral light adaptation, that binocular retroactive masking is due to both peripheral and central effects, and that dichoptic masking is due solely to central retrochiasmal interference. It is proposed that dichoptic retroactive perceptual masking affords a method of investigating central perception time, i.e., the time to consolidate a perceptual experience.     

Absence of color-selectivity in Duncker-type induced visual movement

Using a stationary target and moving field, both consisting of gratings of vertical light and dark bars, Over and Lovegrove (1973) reported that, with monoptic viewing, induced target movement is weaker when the light bars of the two components are different in color. This reduction did not occur for dichoptic viewing, for which the aftereffect was almost negligible. Six experiments are described. The effect of different colors was not confirmed, using a stationary point and moving frame or stationary and moving gratings. Reduced effects for different colors and greatly reduced effects for dichoptic viewing occurred only when there was a stationary boundary to the moving bars of the field grating, as in Over and Lovegrove’s experiment. It is concluded that the effect studied by Over and Lovegrove is not the classical induced movement described by Duncker (1929/1938) but one due to periodic coincidence and noncoincidence of moving and stationary bars in grating patterns. This effect is absent when target and field bars are rendered more distinguishable by different colors.     

Recognition memory and awareness: A large effect of study-test modalities on “know” responses following a highly perceptual orienting task

Abstract

Two experiments investigated the effects of varying the correspondence between presentation and test modes on states of conscious awareness in recognition memory. Experiment 1 used visual test items and showed that auditory and visual study modes differentially affected recollective experience and feelings of familiarity assessed by “remember” and “know” responses accompanying recognition: “know” responses were slightly enhanced following visual presentation, but this was largely offset by a similarly small increase in “remember” responses. Experiment 2 employed conditions designed to maximise any effect on “know” responses of the correspondence between presentation and test modes by using a highly perceptual orienting task at study. Under these conditions, there was a large mode correspondence effect on “know” responses. The results support the idea that “know” responses are particularly sensitive to perceptual factors.     

Color-selective tilt aftereffects with subjective contours

Displays yielding edges visible at sites where the visual stimulus was homogeneous (subjective contours) as well as with edges defined by spatial discontinuities in luminance (real contours) were used to induce the tilt aftereffect. Under monoptic conditions, the aftereffect was larger when the inspection and test edges were shown in the same colored light than when they were shown in different colored lights. Under dichoptic conditions (display of inspection edges to one eye and test edges to the other eye), the aftereffect was reduced in size and it was no longer selective to the color relationship between the inspection and test stimuli. Similar results were obtained with subjective and real contours. In the recent literature, subjective contours have been treated as products of cognitive and inferential operations, whereas neural edge detectors have been implicated in the perception of real contours. The present data suggest, however, the need for caution in attributing the perception of real and subjective contours to fundamentally different processes.     

Word superiority in word detection

Observers searched for a single precued word or its nonword anagram under conditions of rapid serial visual presentation (RSVP). A word advantage was found over a wide range of presentation rates (32-160 msec/frame), under yes-no as well as forced choice conditions, and with both one or two input “channels.” These results suggest that word superiority in word detection occurs at a perceptual locus.     

Stimulus-response compatibility affects auditory Stroop interference

The contribution of stimulus-response compatibility to Stroop interference was tested in an auditory version of the Stroop test. The words “high” and “low” were presented in high and low pitches with either the pitch or the word designated as the relevant dimension. College students categorized the relevant stimulus dimension with a verbal response, a buttonpress, or a pitched hum. Significant interference occurred in the incompatible conditions (pitch-verbal, word-hum, pitch-button), but not in the compatible conditions (pitch-hum, word-verbal, word-button). The results indicated that stimulus-response compatibility was an important determinant of observed interference. It was suggested that stimulus-response incompatibility contributed to the response competition that presumably occurs in Stroop tasks.     

Dichoptic and dichotic micropattern discrimination

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.     

Ear differences in simple reaction time: The influence of attentional factors

Simple motor reaction times (right-handed) to tape-recorded consonant-vowel syllables were obtained from 12 subjects under two conditions of monotic stimulation: “expected” presentation (subject informed as to ear of presentation) and “random” presentation (ear of presentation varied randomly). Significantly faster left ear reaction times were obtained in the “expected” condition. The rank order of subjects' standard dichotic listening task scores correlated negatively with reaction time ear differences in the “expected” presentation condition. Results are discussed in terms of existing theories of response lateralization in simple reaction time tasks, and an expanded hypothesis is offered. Specifically, it is suggested that two or more distinct but potentially overlapping mechanisms may be responsible for observed asymmetries in monotic auditory perception. Both an attentional or lateralized motor response bias and an inherent lateralization of function may operate side by side, differentially activated by task demands, mode of stimulus presentation, and nature of stimuli.     

Behavioral evidence for task-dependent “what” versus “where” processing within and across modalities

Task-dependent information processing for the purpose of recognition or spatial perception is considered a principle common to all the main sensory modalities. Using a dual-task interference paradigm, we investigated the behavioral effects of independent information processing for shape identification and localization of object features within and across vision and touch. In Experiment 1, we established that color and texture processing (i.e., a “what” task) interfered with both visual and haptic shape-matching tasks and that mirror image and rotation matching (i.e., a “where” task) interfered with a feature-location-matching task in both modalities. In contrast, interference was reduced when a “where” interference task was embedded in a “what” primary task and vice versa. In Experiment 2, we replicated this finding within each modality, using the same interference and primary tasks throughout. In Experiment 3, the interference tasks were always conducted in a modality other than the primary task modality. Here, we found that resources for identification and spatial localization are independent of modality. Our findings further suggest that multisensory resources for shape recognition also involve resources for spatial localization. These results extend recent neuropsychological and neuroimaging findings and have important implications for our understanding of high-level information processing across the human sensory systems.     

Discrimination of rotation from linear motion: influence of interference gratings and dichoptic viewing

Observers viewed a screen on which a number of patches containing horizontally moving pixels were presented. Target patches consisted of pixels whose motion simulated the rotation of a cylinder around its Y-axis; distractors, of pixels whose motion was linear. The task was to assess whether a display contained a target patch. Exp. 1 showed that the superposition of the displays with drifting sine-wave gratings interfered with rotation detection in a spatial- and temporal-frequency specific manner. In Exp. 2, dichoptic presentation greatly reduced the interference of the drifting gratings. It is argued on various grounds that the process(es) responsible for the detection and discrimination of rotating structure in depth exists at a low level of the visual system.     

Dichotic and monotic interactions between speech and nonspeech sounds at different stimulus onset asynchronies

Subjects’ identification of stop-vowel “targets” was obtained under monotic and dichotic, forward and backward, masking conditions. Masks, or “challenges,” were another stop-vowel or one of three nonspeech sounds similar to parts of a stop-vowel. Backward masking was greater than forward in dichotic conditions. Forward masking predominated monotically. Relative degree of masking for different challenges suggested that dichotic effects were predicated on interference with processing of a complex temporal array of auditory “features” of the targets, prior to phonetic decoding but subsequent to basic auditory analysis. Monotic effects seemed best interpreted as dependent on relative spectrum levels of nearly simultaneous portions of the two signals.     

Stroop interference with response,comparison, and encoding stages in a sentence-picture comparison task

The paper discusses a Stroop variant of the word-picture comparison task analyzed by Chase and Clark (1971). The locatives above or below were printed at the center of a reference square, and Ss reported “Yes” if there was a word or an array of Xs in the location specified and “No” if there was not. Under the control (Xs) conditions, above displays were classified faster than below displays and true displays faster than false displays. These effects were unaltered when the words “yes” or “no” or “right” or “wrong” were printed in place of the Xs, although there was a small overall increase in response latency under these Stroop conditions that was independent of agreement or disagreement between the distractor and the response to be made. When the locatives up and down were printed on the display, a substantial Stroop effect was observed, and the above-below and true-false effects were eliminated. These results are discussed in relation to theories about the nature of Stroop interference and processes involved in sentence-picture comparisons.     

Recognition in a visuospatial memory task: The effect of presentation

The influence of the mode of presentation (simultaneous vs. sequential) on accuracy and latency of visuospatial recognition was explored in three experiments. In Experiment 1, two groups were administered a visuospatial task in which a number of positions were shown either simultaneously or sequentially (in a random order); memory was tested using a recognition procedure of visuospatial patterns, either identical or different (a single cell displaced). The results showed that (1) performance was higher in the simultaneous than in the sequential presentation, and (2) decision time increased with complexity in the sequential presentation but not in the simultaneous presentation. In Experiment 2, the same task was used in three conditions of presentation, simultaneous, random sequential, and ordered sequential; at test, a single location, rather than a pattern, was presented for recognition. The results showed that (1) performance was higher in the simultaneous and in the ordered sequential presentations than in the random sequential one, and (2) decision time increased with complexity. In Experiment 3, the same task was used in the same three conditions of presentation, simultaneous, random sequential, and ordered sequential; at test either an identical or a “displaced” pattern was presented for recognition. The results showed that (1) performance was equivalent in the three types of presentation, and (2) decision time increased with complexity for “hit” items; different patterns of linear relations were observed for “correct rejections” items. The results are interpreted in terms of the organisation of visuospatial working memory, and three types of encoding—extrafigural spatial encoding, visual pattern encoding, and spatial path encoding—were proposed.