Texture Segregation by Orientation Differences: Colour Sensitive but Not Hue Specific?

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 98-98
Author(s):  
U Leonards ◽  
W Singer
Keyword(s):  
Experimental Psychology ◽  
Human Perception ◽  
Luminance Contrast ◽  
Texture Element ◽  
Feature Maps ◽  
Texture Segregation ◽  
Colour Contrast

Segregation of textures on the basis of orientation differences between texture elements is achieved even when these texture elements differ from their surround only by colour (McIlhagga et al, 1990 Vision Research30 489 – 495). This finding seems to contradict the assumption that colour and orientation are extracted in separate feature maps (eg Treisman and Sato, 1990 Journal of Experimental Psychology: Human Perception and Performance16 459 – 478). To examine whether colour information is evaluated in parallel in different processing streams for the assessment of hue and form, we tested whether texture elements can be segregated if they differ only by specific conjunctions of colour and orientation; texture elements consisted of crosses with their two crossing lines differing in colour. Texture elements defining figure and background had the same coloured composition but the conjunction of colour with the two crossing lines was reversed. Different colour combinations were tested under various luminance contrast conditions, irrespective of the colour combination, segmentation was achieved as long as the two crossing lines of the texture elements differed in luminance. If, however, the different colours of the two crossing lines were approximately equiluminant, segmentation was reduced or impossible. Thus, subjects were able to use for texture segregation conjunctions between luminance and orientation but not between colour and orientation. Our results suggest that colour cannot be associated selectively with differently oriented components of the same texture element. This supports the hypothesis that colour contrast is used in parallel by different processing streams to assess the orientation and hue of contours and reveals limitations in the selectivity with which features are subsequently bound together.

scholarly journals Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification

Eye ◽  
1997 ◽  
Vol 11 (5) ◽  
pp. 713-716
Author(s):  
Michael Wall ◽  
Paul B Donzis
Keyword(s):  
Luminance Contrast ◽  
Colour Contrast

Task-Dependence of Texture-Segregation-Specific VEP Components

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 267-267
Author(s):  
T Meigen
Keyword(s):  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Normal Subjects ◽  
Luminance Contrast ◽  
Auditory Stimuli ◽  
Cognitive Responses ◽  
Texture Segregation ◽  
Task Dependence ◽  
Additional Task ◽  
Temporal Overlap

Recently, texture-segregation-specific components have been isolated in the human visual evoked potential (tsVEPs). As tsVEPs are characterised by a negative peak near 200 ms they occur between luminance-contrast responses (P100) and cognitive responses (P300). The aim of this study was to estimate the temporal overlap of tsVEPs and cognitive VEP components by directing a task to either visual or auditory stimuli. Eight visually normal subjects participated in the experiment. Horizontal and vertical line segments were arranged to yield either an ‘orientation chequerboard’ stimulus or two fields with homogeneous orientations. As auditory stimuli, two tones with different pitches were presented through headphones. Auditory and visual stimuli were temporally uncorrelated, which allowed off-line isolation of VEPs and AEPs by appropriate averaging from the same raw data. VEPs and AEPs were recorded from an array of 13 electrodes ranging from frontal to occipital positions. tsVEPs were isolated under two conditions, where the subjects detected the presence of (a) the orientation chequerboard, or (b) the higher pitch by pressing a button. It was found that (1) tsVEPs could be isolated under both tasks; (2) tsVEPs were strongly modulated by the task; (3) the task-specific modulation occurred in the same time domain as the tsVEP itself, but showed a different topography; (4) AEPs were less modulated by the task. The data suggest that an additional task concerning the gradient content of texture stimuli may modulate the resulting tsVEPs. This may partially account for the interindividual variability in recent tsVEP data, as a comparable task may be introduced tacitly by the subjects.

Priming within the ‘Attentional Blink’ in an RSVP Task

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 26-26
Author(s):  
F K Chua ◽  
J Goh ◽  
G Kek
Keyword(s):  
Attentional Blink ◽  
Sensory Processing ◽  
Experimental Psychology ◽  
Priming Effect ◽  
Human Perception ◽  
Weak Form ◽  
Visual Presentation ◽  
Lower Case Letter ◽  
Lower Case ◽  
Local Interference

Recent experiments (eg M M Chun and M C Potter, 1995 Journal of Experimental Psychology: Human Perception and Performance21 109 – 127; J E Raymond, K L Shapiro, and K M Arnell, 1992 Journal of Experimental Psychology: Human Perception and Performance18 849 – 860) with RSVP (rapid serial visual presentation) suggest that the attentional blink is caused by local interference. We present data from three RSVP experiments that provide further clues regarding the attentional blink. In experiment 1, subjects detected an ‘X’ and then identified a red letter; in experiment 2, subjects had to say whether the first red target was an ‘X’ and then identify a red letter. In experiment 3, subjects identified two red letters. We systematically varied the lag between the first and second targets. On half the trials, we also primed the second target by placing an identical letter in the lag one position (the position after the first target). In experiment 3, we also examined if the priming effect was semantic with a lower case letter. The first two experiments suggest that the priming effect is very short-lived and mainly sensory in nature. The priming effect disappears altogether if the first target is not present. More interestingly, we found that when subjects failed to detect the ‘X’, priming could still happen. The third experiment replicates and extends the results of the first two experiments. We also show that priming, albeit in a weak form, may still happen during the time when the attentional blink is supposed to occur. These results suggest that it is not an inhibition that causes the attentional blink and that sensory processing continues during the blink.

The Effect of Environmental Pitch on Perceived Optic Slant and Eye Level: Lines vs Dots

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 151-151
Author(s):  
A E Stoper ◽  
J Randle ◽  
M M Cohen
Keyword(s):  
Direct Effect ◽  
Experimental Psychology ◽  
Human Perception ◽  
Vertical Line ◽  
Line Segments ◽  
Level Lines ◽  
Pitch Dimension ◽  
Zero Effect

Visually perceived eye level (VPEL) has been shown to be strongly affected by the pitch of the visible environment (Stoper and Cohen, 1989 Perception & Psychophysics46 469 – 475), even if this environment consists of only two luminous lines pitched from the vertical (Matin and Li, 1992 Journal of Experimental Psychology: Human Perception and Performance18 257 – 289). Here, two luminous vertical lines or 32 randomly distributed luminous dots were mounted on a plane that was viewed monocularly and was pitched (slanted in the pitch dimension) 30° forward or backward from the vertical. In addition to measuring the VPEL, we measured the perceived optic slant (rather than the perceived geographic slant) of this plane by requiring each of our ten subjects to set a target to the visually perceived near point (VPNP) of the plane. We found that, for the lines, VPNP shifted 50% and VPEL shifted 26% of the physical pitch of the plane. For the dots, VPNP shifted 28% but VPEL shifted only 8%. The effect of the dots on VPEL was weaker than might have been predicted by their effect on VPNP, which was used to indicate perceived optic slant. The weakness of the effect of the dots on VPEL implies that changes in VPEL result from a direct effect of the stimuli on VPEL, rather than one mediated by the perceived optic slant of the plane. The non-zero effect of the dots shows that pitched from vertical line segments are not necessary to shift VPEL.

Cross-Modal and Non-Sensory Influences on Auditory Streaming

Perception ◽  
10.1068/p5035 ◽  
2003 ◽  
Vol 32 (11) ◽  
pp. 1393-1402 ◽  
Author(s):  
Robert P Carlyon ◽  
Christopher J Plack ◽  
Deborah A Fantini ◽  
Rhodri Cusack
Keyword(s):  
Auditory Stimulus ◽  
Experimental Psychology ◽  
Visual Stimuli ◽  
Human Perception ◽  
Tone Sequence ◽  
Visual Task ◽  
Auditory Streaming ◽  
Visual Targets

Carlyon et al (2001 Journal of Experimental Psychology: Human Perception and Performance27 115–127) have reported that the buildup of auditory streaming is reduced when attention is diverted to a competing auditory stimulus. Here, we demonstrate that a reduction in streaming can also be obtained by attention to a visual task or by the requirement to count backwards in threes. In all conditions participants heard a 13 s sequence of tones, and, during the first 10 s saw a sequence of visual stimuli containing three, four, or five targets. The tone sequence consisted of twenty repeating triplets in an ABA–ABA … order, where A and B represent tones of two different frequencies. In each sequence, three, four, or five tones were amplitude modulated. During the first 10 s of the sequence, participants either counted the number of visual targets, counted the number of (modulated) auditory targets, or counted backwards in threes from a specified number. They then made an auditory-streaming judgment about the last 3 s of the tone sequence: whether one or two streams were heard. The results showed more streaming when participants counted the auditory targets (and hence were attending to the tones throughout) than in either the ‘visual’ or ‘counting-backwards’ conditions.

Contrast Polarity Affects Performance after Figure-Ground Coding

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 243-243
Author(s):  
K J Linnell ◽  
G W Humphreys
Keyword(s):  
Experimental Psychology ◽  
Reaction Times ◽  
Human Perception ◽  
Opposite Polarity ◽  
Regular Polygons ◽  
Target Element ◽  
Dramatic Effect ◽  
Contrast Polarity ◽  
Search Experiment ◽  
Opposite Contrast

Gilchrist et al (1997 Journal of Experimental Psychology: Human Perception and Performance23 464 – 480) proposed that some aspects of grouping are relatively insensitive to variations in contrast polarity between the elements to be grouped. We assessed the contrast-polarity sensitivity of grouping in a visual search experiment. Display elements were corner-brackets arranged at the vertices of regular polygons (see Donnelly et al, 1991 Journal of Experimental Psychology: Human Perception and Performance17 561 – 570), either aligned with polygon sides (strong-grouping condition), rotated through 20° (weak-grouping condition), or rotated through 180° (open condition). The background was grey; on same-contrast-polarity trials, elements were either all white or all black; on opposite-polarity trials, each element was white and black. The task was to detect a target element rotated 180° with respect to the others. With weak grouping present, opposite contrast polarity slowed reaction times dramatically: they were as slow as those to open displays. A second experiment in which display elements were pacmen showed that the contrast-polarity effect on performance is modulated by figure - ground relations: the dramatic effect of contrast polarity in the weak-grouping condition disappeared, presumably because search focused on the uniform grey illusory surface. These results suggest that grouping operates automatically to produce figure - ground coding of displays, but that contrast polarity differences within a figural surface affect the output of these codes to systems concerned with perceptual discriminations.

Isoluminant Colour Contrast Does Not Fill in Surfaces

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 40-40
Author(s):  
B Dresp ◽  
C Wehrhahn
Keyword(s):  
Luminance Contrast ◽  
Opposite Polarity ◽  
The Other ◽  
Test Surface ◽  
Colour Contrast ◽  
Mixed Polarity ◽  
Polarity Condition ◽  
Matching Procedure ◽  
The Mean ◽  
Neurophysiological Basis

It has been suggested (Livingstone and Hubel, 1988 Science240 740 – 749) that the ‘colour-blind’ magnocellular pathways generate the neurophysiological basis of surfaces with illusory contours since the latter do not seem to be perceived in inducing configurations of a given colour which is isoluminant with regard to the colour of the background (equiluminant colour contrast). However, psychophysical data allowing us to assess the relative visibility of illusory surfaces in coloured stimuli with luminance contrast compared to configurations with equiluminant colour contrast are not yet available. We designed a colour-matching experiment where ten naive observers had to adjust the intensity of a red illusory surface so that it appeared to match the intensity of the red background. The configurations used were Kanizsa squares with green inducing elements, isoluminant or not with regard to the background. Isoluminance was assessed individually for each observer by means of a classical flicker test. A brightness-matching procedure was applied to configurations of achromatic inducers on a grey background. In this case, the inducers had either all the same contrast polarity (light), or both polarities (light and dark) within a given configuration. Luminance contrast in the achromatic configuration with only one polarity was the same as in the non-isoluminant colour condition. Luminance contrasts of light and dark inducers in the mixed-polarity condition were physically balanced. The results show that the mean point of subjective equality (PSE) of the test surface corresponds to the physical intensity of the background with equiluminant colour contrast only, indicating the absence of an apparent surface in this condition. This result supports the idea that magnocellular pathways in the human visual system mediate the neurophysiological genesis of illusory surfaces. In all the other stimulus conditions, the PSE does not correspond to the physical intensity of the background. Matching ‘errors’ are significantly stronger in the achromatic conditions, but, paradoxically, strongest in the condition with balanced contrasts of opposite polarity. This finding suggests that luminance contrast is not the only determinant of the perceived strength of illusory surfaces.

Sign in / Sign up

Export Citation Format

Share Document