Figure-Ground Assignment of Stereo-Defined Contours Affects the Ease of Symmetry and Translation Detection

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 366-366
Author(s):  
R E Sorensen ◽  
J Driver
Keyword(s):  
Experimental Psychology ◽  
Human Perception ◽  
Symmetry Detection ◽  
Relative Ease ◽  
Contrast Polarity ◽  
Random Dot Stereograms ◽  
Contour Following ◽  
Figural Assignment

When figure - ground assignment reverses for a given contour, convexities along it become concavi- ties, and vice versa. Baylis and Driver (1995 Journal of Experimental Psychology: Human Perception and Performance21 1323 – 1342) examined the possible implications of this effect for the perception of symmetry between contours. Using contrast reversal to determine figure - ground assignment, they argued that the ease of detecting symmetry between two contours depends on whether convexities along them match following figural assignment. However, their results might be attributed to the contrast polarity of individual edges instead. We used random-dot stereograms to vary figure - ground assignment for edges while holding contrast polarity constant. By placing the areas on either side of each contour at various depth planes, conditions were created in which the convex parts yielded for related contours either matched or mismatched following figural assignment. Particular depth arrangements which yielded matching convex parts for symmetrical contours yielded mismatching parts for translated contours, and vice versa. The results confirmed that the relative ease of symmetry-detection versus translation-detection depends on the convex parts yielded for each contour following figural assignment. These findings suggest that the perception of symmetry between contours arises only after they have been assigned to a figure on one of their sides, and is based on a higher-level interpretation of each contour in terms of convex parts, rather than lower-level properties of the image.

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.

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.

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.

The Effects on Bilateral-Symmetry Detection of Multiple Symmetry, near Symmetry, and Axis Orientation

Perception ◽  
1997 ◽  
Vol 26 (7) ◽  
pp. 891-904 ◽  
Author(s):  
Peter Wenderoth
Keyword(s):  
Response Bias ◽  
Human Perception ◽  
Negative Stimulus ◽  
Bilateral Symmetry ◽  
Symmetry Detection ◽  
Axis Orientation ◽  
Second Stage ◽  
Asymmetrical Pattern ◽  
Stage Process ◽  
Axes Of Symmetry

Palmer and Hemenway (1978 Journal of Experimental Psychology: Human Perception and Performance4 691–702) reported that shapes with multiple axes of symmetry are processed faster than those with single symmetry even when trials are blocked so that the subject knows that any symmetry axis will be vertical. Because their model of symmetry detection postulated a two-stage process in which all orientations are searched crudely at first, in no particular order, followed by second-stage scrutiny, the continued salience of multiple over single symmetry with blocking could not be explained. They claimed that stimuli with multiple axes of symmetry have an additional ‘goodness’. Four experiments are reported in which it is demonstrated that both sensitivity ( d′) and response bias ( β) vary considerably in symmetry detection, not just as a function of the positive (symmetrical) stimuli used but also as a function of the negative or conjugate instances selected. Although stimuli with multiple axes of symmetry may well have extra salience due to pattern ‘goodness’, this factor may have been confounded with response bias in Palmer and Hemenway's experiments. It is suggested that several of their—as well as other researchers—results could be due to some combination of the effects of type of positive stimulus, type of negative stimulus, and response bias directed towards responding positively to highly symmetrical stimuli in a mix of less symmetrical stimuli. Palmer and Hemenway appear to have been correct in suggesting that subjects are more sensitive to quadruple than single symmetry, but the experiments indicate that subjects are also more willing to respond “symmetrical” to stimuli with quadruple symmetry when trials are not blocked, as in Palmer and Hemenway's experiment 1. However, it is demonstrated that the latter effect can be removed by blocking trials so that only one class of symmetrical pattern and one class of asymmetrical pattern occur in any block.

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.

Estimating Perception of Distance : Applied Sequential Methodologies in Experimental Psychology

2005 ◽  
Vol 56 (1-4) ◽  
pp. 35-56 ◽  
Author(s):  
Nitis Mukhopadhyay
Keyword(s):  
Experimental Psychology ◽  
Human Perception ◽  
Crime Scene ◽  
Reference Points ◽  
Designed Experiments ◽  
Data Analyses ◽  
Straight Line ◽  
Important Input ◽  
The Individual ◽  
Associated Data

Summary An eyewitness's description of a missing criminal, for example, is very crucial for apprehending the individual. But, some accounts may be unreliable if it turned out that the witness was ‘far away’ from a crime scene. Estimation of the perception of “distance” can be an important input in many situations including this one. We ran a number of designed experiments, collected data, and analyzed them in order to understand how individuals perceived “distance”. These experiments and associated data analyses have some clear messages: When a subject was asked to guess the length of an object such as a straight line or a ruler, we found time and again that one's answer routinely depended upon (i) presence or absence of landmarks or reference points, and (ii) what one had thought that was being shown rather than what the true item really was. More investigations in experimental psychology are deemed essential in one's thorough understauding of human perception of “distance”.

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