Isoluminance and contingent color aftereffects

In the typical induction of the orientation-contingent color aftereffect (CCAE), the stimuli are composed of elements that differ in both color and luminance. Three experiments are reported that show that chromatic contrast between stimulus elements is insufficient for the induction of the orientation-CCAE and that luminance contrast is necessary. These experiments expand on previous research concerned with the role of luminance contrast in the induction of orientation-CCAEs by eliminating alternative explanations.     

Persistence of simple and contingent motion aftereffects

Jones and Holding (1975) showed that orientation-contingent color aftereffects can persist for at least 3 months, but are depleted by repeated testing. We applied the same paradigm to a simple motion aftereffect (MAE) and found that it can persist for up to 1week and is only slightly diminished by testing. It was further found that simple MAEs appear to persist longer than color-contingent MAEs, although when procedures for inducing and measuring both kinds of aftereffect are equalized, contingent MAEs last longer. Finally, no tendency was found for color-contingent MAEs to diminish with repeated testing. Although both simple and color-contingent MAEs can be relatively persistent, there are certain differences between them. Furthermore, contingent aftereffects should not be considered interchangeable, as there appear to be large differences in the persistence of orientation-contingent color aftereffect and color-contingent MAEs.     

Biases of spatial attention in vision and audition

Neurologically normal observers misperceive the midpoint of horizontal lines as systematically leftward of veridical center, a phenomenon known as pseudoneglect. Pseudoneglect is attributed to a tonic asymmetry of visuospatial attention favoring left hemispace. Whereas visuospatial attention is biased toward left hemispace, some evidence suggests that audiospatial attention may possess a right hemispatial bias. If spatial attention is supramodal, then the leftward bias observed in visual line bisection should also be expressed in auditory bisection tasks. If spatial attention is modality specific then bisection errors in visual and auditory spatial judgments are potentially dissociable. Subjects performed a bisection task for spatial intervals defined by auditory stimuli, as well as a tachistoscopic visual line bisection task. Subjects showed a significant leftward bias in the visual line bisection task and a significant rightward bias in the auditory interval bisection task. Performance across both tasks was, however, significantly positively correlated. These results imply the existence of both modality specific and supramodal attentional mechanisms where visuospatial attention has a prepotent leftward vector and audiospatial attention has a prepotent rightward vector of attention. In addition, the biases of both visuospatial and audiospatial attention are correlated.     

The associative basis of contingent color aftereffects.

According to a conditioning analysis of the orientation-contingent color aftereffect (McCollough effect, ME), orientation stimulus (grids) become associated with color. Contrary to this interpretation are reports that simple forms cannot be used to elicit illusory color and that the ME is not degraded by decreasing the grid-color correlation. The present results indicate: (a) Form stimuli can contingently elicit color aftereffects; (b) even a non-patterned stimulus--the lightness of a frame surrounding a colored area--can contingently elicit color aftereffects; (c) this frame lightness-contingent aftereffect, like the ME, persists for at least 24 hr; and (d) the frame lightness-contingent aftereffect can be used to demonstrate that correlational manipulations affect the ME, as they affect other types of conditional responses.     

The temporal cross-capture of audition and vision

We report that when a flash and audible click occur in temporal proximity to each other, the perceived time of occurrence of both events is shifted in such a way as to draw them toward temporal convergence. In one experiment, observers judged when a flash occurred by reporting the clock position of a rotating marker. The flash was seen significantly earlier when it was preceded by an audible click and significantly later when it was followed by an audible click, relative to a condition in which the flash and click occurred simultaneously. In a second experiment, observers judged where the marker was when the click was heard. When a flash preceded or followed the click, similar but smaller capture effects were observed. These capture effects may reveal how temporal discrepancies in the input from different sensory modalities are reconciled and could provide a probe for examining the neural stages at which evoked responses correspond to the contents of conscious perception.     

Nonspatial attentional shifts between audition and vision

This study investigated nonspatial shifts of attention between visual and auditory modalities. The authors provide evidence that the modality of a stimulus (S1) affected the processing of a subsequent stimulus (S2) depending on whether they shared the same modality. For both vision and audition, the onset of S1 summoned attention exogenously to its modality, causing a delay in processing S2 in a different modality. That undermines the notion that auditory stimuli have a stronger and more automatic alerting effect than visual stimuli (M. I. Posner, M. J. Nissen, & R. M. Klein, 1976). The results are consistent with other recent studies showing cross-modal attentional limitation. The authors suggest that such cross-modal limitation can be produced by simply presenting S1 and S2 in different modalities and that central processing mechanisms are also, at least partially, modality dependent.     

Effective luminance contrast as a parameter in contingent aftereffects

Variation in the magnitude of contingent aftereffects was explored as a function of the luminance contrast ratio profile of inspection stimuli. Positive contrast stimuli (chromatic bars interspersed with achromatically brighter bars) produced substantially attenuated aftereffects compared with negative contrast stimuli (chromatic and dark bars). This attenuation was hypothesized to result from retinal image deterioration of positive contrast gratings due to retinal reflection/scatter. In a second experiment, subjects selected for their light retinal pigmentation manifested substantial enhancement of the asymmetry between the aftereffects generated by positive and negative contrast gratings. Those with dark fundus pigmentation showed symmetrical aftereffects.     

The temporal cross-capture of audition and vision.

We report that when a flash and audible click occur in temporal proximity to each other, the perceived time of occurrence of both events is shifted in such a way as to draw them toward temporal convergence. In one experiment, observers judged when a flash occurred by reporting the clock position of a rotating marker. The flash was seen significantly earlier when it was preceded by an audible click and significantly later when it was followed by an audible click, relative to a condition in which the flash and click occurred simultaneously. In a second experiment, observers judged where the marker was when the click was heard. When a flash preceded or followed the click, similar but smaller capture effects were observed. These capture effects may reveal how temporal discrepancies in the input from different sensory modalities are reconciled and could provide a probe for examining the neural stages at which evoked responses correspond to the contents of conscious perception.     

Hearing gestures, seeing music: vision influences perceived tone duration

Percussionists inadvertently use visual information to strategically manipulate audience perception of note duration. Videos of long (L) and short (S) notes performed by a world-renowned percussionist were separated into visual (Lv, Sv) and auditory (La, Sa) components. Visual components contained only the gesture used to perform the note, auditory components the acoustic note itself. Audio and visual components were then crossed to create realistic musical stimuli. Participants were informed of the mismatch, and asked to rate note duration of these audio-visual pairs based on sound alone. Ratings varied based on visual (Lv versus Sv), but not auditory (La versus Sa) components. Therefore while longer gestures do not make longer notes, longer gestures make longer sounding notes through the integration of sensory information. This finding contradicts previous research showing that audition dominates temporal tasks such as duration judgment.     

Movement aftereffects contingent on color,intensity, and pattern

We have found contingent movement aftereffects (CMAEs) lasting several days, contingent upon the color, intensity, and stripe width of moving patterns. Ss adapted for 10 min to a patterned disk rotating clockwise under red light, alternating every 10 sec with counterclockwise under green light. When stopped, the disk then appeared to rotate counterclockwise under red light and clockwise under green light. The effect lasted only a second or two, reappearing each time the field’s color was changed. But it increased in strength over the first 1/2 hand was still present 1 or 2 days later. Color transposition effects were found: after adaptation to red-clockwise (long wavelength) alternating with green-counterclockwise (short wavelength), a stationary yellow (long wavelength) test field appeared to rotate counterclockwise and a blue (short wavelength) field appeared to rotate clockwise. Relative, not absolute, color of the test triggered the CMAE. Similar CMAEs and transposition effects were produced by pairing direction of movement with intensity, with width of moving stripes and with orientation of a stationary grating projected onto a rotating patterned disk.     

Dichoptic induction of movement aftereffects contingent on color and on orientation

Some comparative experiments on the dichoptic induction of the movement aftereffect (MAE) contingent on color and the MAE contingent on orientation are reported. Colorcontingent movement aftereffects could be evoked only when the eye which had viewed color during adaptation also viewed color during test sessions. When the apparent color of the test field was changed by binocular color rivalry, contingent movement aftereffects (CMAEs) appropriate to the suppressed color were reported. After dichoptic induction of the orientation-contingent MAE, aftereffects could be obtained whether the eliciting gratings and stationary test fields were presented together to either eye alone or were dichoptically viewed.     

Asymmetric transfer of prototype information between vision and audition

Specific and nonspecific transfer of pattern class concept information between vision and audition was examined. In Experiment 1, subjects learned visually or auditorily to distinguish between two pattern classes that were either the same as or different from the test classes. All subjects were then tested on the auditory classification of 50 patterns. Specific intramodal and cross-modal transfer was noted; subjects trained visually and auditorily on the test classes were equivalent in performance and more accurate than untrained controls. In Experiment 2, the training of Experiment 1 was repeated, but subjects were tested visually. There was no evidence of auditory-to-visual transfer but some suggestion of nonspecific transfer within the visual modality. The asymmetry of transfer is discussed in terms of the modality into which patterns are most likely translated for the cross-modal tasks and in terms of the quality of prototype formation with visual versus a,ditory patterns.     

Temporal factors in audition and vision: A functional emphasis

Sixty-four subjects were tested in an experiment relating temporal factors to the modality effect. The experiment involved both an immediate recall and a recognition phase. Recall scores supported a functional view of the modality effect, while the one-and two-store models only partially predicted the data. The recognition data could only be accounted for in functional terms. A non-parametric compatibility score was suggested to capture the recognition performance. The effect of a shift of input mode (in Phase I) to test mode (in Phase II) was also analyzed.     

Discriminating speech rhythms in audition,vision, and touch

We investigated the extent to which people can discriminate between languages on the basis of their characteristic temporal, rhythmic information, and the extent to which this ability generalizes across sensory modalities. We used rhythmical patterns derived from the alternation of vowels and consonants in English and Japanese, presented in audition, vision, both audition and vision at the same time, or touch. Experiment 1 confirmed that discrimination is possible on the basis of auditory rhythmic patterns, and extended it to the case of vision, using ‘aperture-close’ mouth movements of a schematic face. In Experiment 2, language discrimination was demonstrated using visual and auditory materials that did not resemble spoken articulation. In a combined analysis including data from Experiments 1 and 2, a beneficial effect was also found when the auditory rhythmic information was available to participants. Despite the fact that discrimination could be achieved using vision alone, auditory performance was nevertheless better. In a final experiment, we demonstrate that the rhythm of speech can also be discriminated successfully by means of vibrotactile patterns delivered to the fingertip. The results of the present study therefore demonstrate that discrimination between language's syllabic rhythmic patterns is possible on the basis of visual and tactile displays.     

Lessons from beyond vision (sounds and audition)

Recent work on non-visual modalities aims to translate, extend, revise, or unify claims about perception beyond vision. This paper presents central lessons drawn from attention to hearing, sounds, and multimodality. It focuses on auditory awareness and its objects, and it advances more general lessons for perceptual theorizing that emerge from thinking about sounds and audition. The paper argues that sounds and audition no better support the privacy of perception’s objects than does vision; that perceptual objects are more diverse than an exclusively visual perspective suggests; and that multimodality is rampant. In doing so, it presents an account according to which audition affords awareness as of not just sounds, but also environmental happenings beyond sounds.     

Apparent velocity of motion aftereffects in central and peripheral vision

Adapting to a drifting grating (temporal frequency 4 Hz, contrast 0.4) in the periphery gave rise to a motion aftereffect (MAE) when the grating was stopped. A standard unadapted foveal grating was matched to the apparent velocity of the MAE, and the matching velocity was approximately constant regardless of the visual field position and spatial frequency of the adapting grating. On the other hand, when the MAE was measured by nulling with real motion of the test grating, nulling velocity was found to increase with eccentricity. The nulling velocity was constant when scaled to compensate for changes in the spatial 'grain' of the visual field. Thus apparent velocity of MAE is constant across the visual field, but requires a greater velocity of real motion to cancel it in the periphery. This confirms that the mechanism underlying MAE is spatially-scaled with eccentricity, but temporally homogeneous. A further indication of temporal homogeneity is that when MAE is tracked, by matching or by nulling, the time course of temporal decay of the aftereffect is similar for central and for peripheral stimuli.     

Category contingent aftereffects for faces of different races, ages and species

Exposure to faces biases perceptions of subsequently viewed faces such that normality judgments of similar faces are increased. Simultaneously inducing such an aftereffect in opposite directions for two groups of faces might indicate discrete responding of the neural populations coding for those groups. Here we show such "category contingent" aftereffects following exposure to faces differing in eye-spacing (wide versus narrow) for European versus African faces, adult versus infant faces, and human versus monkey faces. As aftereffects reflect changes in responses of neural populations that code faces, our results may then suggest that functionally distinct neural populations code faces of different ages, races and species and that the human brain potentially contains discrete representations of these categories.     

Neuroimaging of multisensory processing in vision,audition, touch,and olfaction

The development of neuroimaging methods has had a significant impact on the study of the human brain. Functional MRI, with its high spatial resolution, provides investigators with a method to localize the neuronal correlates of many sensory and cognitive processes. Magneto- and electroencephalography, in turn, offer excellent temporal resolution allowing the exact time course of neuronal processes to be investigated. Applying these methods to multisensory processing, many research laboratories have been successful in describing cross-sensory interactions and their spatio-temporal dynamics in the human brain. Here, we review data from selected neuroimaging investigations showing how vision can influence and interact with other senses, namely audition, touch, and olfaction. We highlight some of the similarities and differences in the cross-processing of the different sensory modalities and discuss how different neuroimaging methods can be applied to answer specific questions about multisensory processing.Edited by: Marie-Hélène Giard and Mark Wallace     

Measurement of visual aftereffects and inferences about binocular mechanisms in human vision

There is conflicting evidence concerning the characteristics of binocular channels in the human visual system with respect to the existence of a 'pure' binocular channel that responds only to simultaneous stimulation of both eyes. Four experiments were conducted to resolve these discrepancies and to evaluate the evidence for the existence of such an exclusive binocular channel. In the first three studies, tilt aftereffects were measured after monocular adaptation. The relative sizes of the direct, interocularly transferred, and binocular aftereffects were not influenced by the configuration of the adapting pattern (experiment 1), or by the eye used for adaptation (experiment 2). There were also consistent interobserver differences in the relative sizes of the aftereffect seen after monocular adaptation (experiment 3). Taken together, these data raise questions about the appropriateness of a monocular adaptation paradigm for evaluating the presence of a pure binocular channel in observers with normal binocular vision. In experiment 4, in which the paradigm of alternating monocular adaptation was used, data were obtained that are consistent with the presence of a pure binocular channel.