Multidimensional scaling of subjective colors by color-blind observers

Temporal coding theories of color vision suggest explanations of flicker-induced subjective colors such as those that appear on Benham’s disk. If color blindness were due simply to photopigment anomalies, then subjective colors might be elicited by central patterns of neural activity in color-blind observers that mimic those which the cones normally produce in colornormal observers. We had color-normal and color-blind observers scale subjective colors like those on Benham’s disk for similarity. The inferred color spaces for six normal observers resembled the familiar hue circle, but the spaces for five red-green-deficient observers were compressed along the red-green axis. This is consistent with the position that flicker colors are due to retinal processes, and suggests that color blindness may involve variations of the central nervous system in addition to photopigment anomalies.     

“Transient structures”: The effects of practice and distractor grouping on within-dimension conjunction searches

It has been stated that whereas between-dimension (color × orientation) conjunctions can be searched in a “parallel” fashion, within-dimension (color × color) conjunctions are necessarily searched in a “serial self-terminating” fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers’ performance was characterized by a shallow reaction time (RT) × set size slope; in the second condition, observers’ performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT × set size slope characterized observers’ search for a color × color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models— namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT × set size slope functions to distinguish between preattentive versus attentive search.     

Color spaces of color-normal and color-abnormal observers reconstructed from response times and dissimilarity ratings

With multidimensional scaling analysis, color spaces were reconstructed from reaction times (RTs) required to make same-different judgements of pairs of 15 equiluminant colors and from dissimilarity ratings between them. In addition to normal trichromats, observers with red-green color deficiency were tested. Two main purposes were served by this study: (1) to compare spatial representations of colors derived from discriminative RTs with those derived from dissimilarity measures and (2) to examine whether the task may selectively affect the dimension reflecting, in color-abnormal spaces, the deficient red-green mechanism. Contradicting our hypothesis of lower dimensionality of RT spaces, as compared with rating spaces, no consistent differences in solution dimensionality were found. However, configurations derived from the two measures diverged. The rating procedure yielded the most logical results for recovering color space. The RT configuration revealed contraction in the tritanopic direction, indicating longer color processing when the short-wavelength mechanism is involved, and in addition, for color-abnormal observers, clustering in the protanopic and deuteranopic directions, indicating even longer processing by the deficient red-green mechanism. This finding implies that RTs are suitable for detecting temporal differences in color processing but, for that very same reason, rather ill-suited for reconstructing color spaces.     

Men's fabric preferences related to age, inherent color vision, and perceptual disembedding ability

Non-random samples of 27 color-normal and 27 color-blind men between the ages of 18 and 52 were administered measures of color vision, fabric preferences, and perceptual disembedding (field dependence). Pearson product-moment correlation and analysis of variance were used to test associations among the variables. Results showed the rank order of men's fabric preferences from least to most preferred were pattern, large design, tint, textured, small design, shade, smooth, and plain. There was one significant relationship between age and a preference for tints. No significant relationships were found among fabric preferences and color vision, fabric preference and field dependence, or age and field dependence. Color-blind men were significantly more field-independent than color-normal men in the sample. It was concluded that social as opposed to inherent factors helped to determine men's fabric preferences.     

Discrimination and matching within and between hues measured by reaction times: some implications for categorical perception and levels of information processing

Summary Same-different reaction times (RTs) were obtained for pairs of color samples ranging perceptually from blue to green. In Experiment 1, observers responded with same if both stimuli in a pair were from the same hue category (i.e., blue-blue or green-green) or different if the two stimuli were from different hue categories (i.e., blue-green or green-blue). RT for same responses was faster for pairs of physically identical stimuli (A-A) than for pairs of physically different stimuli (A-a) belonging to the same hue. RT for different responses was faster for larger physical differences across a boundary between hues (A-B 6 step) than for smaller physical differences (A-B 2 step). Experiment 2 replicated and extended these findings: In one phase observers matched pairs of stimuli as same or different by categorical similarity as in Experiment 1, and in a second phase observers matched the same stimulus pairs, this time by physical similarity. Matching by categorical similarity replicated the pattern of results found in Experiment 1. Matching by physical similarity showed that RTs for different responses were equivalently fast independent of the physical difference between A-B pairs, but were faster for A-B than for A-a comparisons. Further, matching identity was faster under categorical match instructions than under physical match instructions. Results of the two experiments support a model of parallel processing of physical and categorical stimulus information in color perception. Further, these reaction-time data and their implications in color perception (for hues) parallel reaction-time data and their implications in speech perception (for phonemes).     

Segregation by color and stereoscopic depth in three-dimensional visual space

Two experiments were conducted to investigate how color and stereoscopic depth information are used to segregate objects for visual search in three-dimensional (3-D) visual space. Eight observers were asked to indicate the alphanumeric category (letter or digit) of the target which had its unique color and unique depth plane. In Experiment 1, distractors sharing a common depth plane or a common color appeared in spatial contiguity in thexy plane. The results suggest that visual search for the target involves examination of kernels formed by homogeneous items sharing the same color and depth. In Experiment 2, thexy contiguity of distractors sharing a common color or a common depth plane was varied. The results showed that when target-distractor distinction becomes more difficult on one dimension, the other dimension becomes more important in performing visual search, as indicated by a larger effect on search time. This suggests that observers can make optimal use of the information available. Finally, color had a larger effect on search time than did stereoscopic depth. Overall, the results support models of visual processing which maintain that perceptual segregation and selective attention are determined by similarity among objects in 3-D visual space on both spatial and nonspatial stimulus dimensions.     

COLOR SPACE OF NORMALLY SIGHTED AND COLOR-DEFICIENT OBSERVERS RECONSTRUCTED FROM COLOR NAMING

Abstract— An experimental procedure based an the color-naming method introduced by Boynton, Schafer, and Neun (1964) was used to study the color appearance of equilumtnant spectral stimuli in observers with congenital red-green color deficiencies, as well as in normal trichromats. Subjects' responses (choice of one or more labels from the set red, yellow, green, blue, and white) were converted to numeric scores, which were used to estimate subjective difference between pairs of colors Individual subjects' matrices were processed by means of multidimensional scaling. As in the direct rating of color dissimilarities in normal trichromats. (Sokolov & Izmatlov, 1983), and color-deficient observers (Paramei Izmailov, & Sokolov, 1991), these indirectly obtained measures yielded a color space in which three dimensions appear to be necessary and sufficient. The dimensions are interpreted as evidence for red-green, Mae-yellow, and achromatic (saturation) sub-systems. Based on the color-naming technique, three-dimensional spaces were reconstructed for the color-deficient observers. These results were compared with those obtained by Helm (1964). It is argued that retaining more than one (blue-yellow) dimension in the color spaces of such observers provider additional information indicating preservation of residual red-green discrimination accompanied by finer discrimination of chroma than in normal trichromats. The spherical model of color discrimination developed for normal trichromats (lzmailov & Sokolov, 1991) is shown to be valid for color-deficient subjects as well and may be useful as a framework for differentiating proton and deutan types of color deficiency. Color-naming functions, which seem not to reveal a differentiation between protans and deutans, provide results form which this differentiation can be extracted in reconstructed color spaces.     

Response time modeling reveals multiple contextual cuing mechanisms

Contextual cuing refers to a response time (RT) benefit that occurs when observers search through displays that have been repeated over the course of an experiment. Although it is generally agreed that contextual cuing arises via an associative learning mechanism, there is uncertainty about the type(s) of process(es) that allow learning to influence RT. We contrast two leading accounts of the contextual cuing effect that differ in terms of the general process that is credited with producing the effect. The first, the expedited search account, attributes the cuing effect to an increase in the speed with which the target is acquired. The second, the decision threshold account, attributes the cuing effect to a reduction in the response threshold used by observers when making a subsequent decision about the target (e.g., judging its orientation). We use the diffusion model to contrast the quantitative predictions of these two accounts at the level of individual observers. Our use of the diffusion model allows us to also explore a novel decision-level locus of the cuing effect based on perceptual learning. This novel account attributes the RT benefit to a perceptual learning process that increases the quality of information used to drive the decision process. Our results reveal both individual differences in the process(es) involved in contextual cuing but also identify several striking regularities across observers. We find strong support for both the decision threshold account as well as the novel perceptual learning account. We find relatively weak support for the expedited search account.     

Overprediction and blocking in the McCollough aftereffect

The Rescorla-Wagner theory (Rescorla & Wagner, 1972) of associative learning offers specific predictions about the associative strength of CS-US pairs when two or more CSs are conditioned to the same US separately and subsequently paired in a compound with the same US. The magnitude of orientation-contingent color aftereffects (AEs) was used as an index of associative strength in this study. The results of experiments using an "overprediction" (Rescorla, 1970) and a "blocking" (Kamin, 1969) paradigm conformed to the predictions of the Rescorla-Wagner theory. In Experiment 1, AEs were established simultaneously for horizontal-vertical and diagonal patterns. When observers subsequently viewed compound induction patterns, AE magnitude was found to be significantly decreased, relative to a condition in which observers did not view such an induction pattern. In Experiment 2, AE magnitude for a given test pattern following inspection of compound induction stimuli was significantly reduced by inspection of the other component prior to viewing the compound induction stimuli. The applicability of associative learning and feature-adaptation models of the McCollough effect is discussed.     

Binocularity and visual search—Revisited

Binocular rivalry is a phenomenon of visual competition in which perception alternates between two monocular images. When two eye’s images only differ in luminance, observers may perceive shininess, a form of rivalry called binocular luster. Does dichoptic information guide attention in visual search? Wolfe and Franzel (Perception & Psychophysics, 44(1), 81–93, 1988) reported that rivalry could guide attention only weakly, but that luster (shininess) “popped out,” producing very shallow Reaction Time (RT) × Set Size functions. In this study, we have revisited the topic with new and improved stimuli. By using a checkerboard pattern in rivalry experiments, we found that search for rivalry can be more efficient (16 ms/item) than standard, rivalrous grating (30 ms/item). The checkerboard may reduce distracting orientation signals that masked the salience of rivalry between simple orthogonal gratings. Lustrous stimuli did not pop out when potential contrast and luminance artifacts were reduced. However, search efficiency was substantially improved when luster was added to the search target. Both rivalry and luster tasks can produce search asymmetries, as is characteristic of guiding features in search. These results suggest that interocular differences that produce rivalry or luster can guide attention, but these effects are relatively weak and can be hidden by other features like luminance and orientation in visual search tasks.     

Chromatic information processing: Rate depends on stimulus location in the category and psychological complexity

Summary Colors are typically categorized, and color sensations can be conceived to lie on a continuum of psychological complexity from simple, sensations provoked by colors that fall near the centers of color categories and that convey predominately a single percept (like blue), to complex, sensations provoked by colors that fall near boundaries between color categories and that convey two percepts (like blue-green). In three experiments we assessed the effect of the location of colors in a category (their psychological complexity) on the rate at which observers identified and classified them. In Experiment 1, observers named category center colors faster than boundary colors. A subsidiary experiment with range-shifted stimuli showed that observers were not merely bisecting a stimulus continuum. In Experiment 2, observers classified a variety of category centers more rapidly than a variety of boundaries. In Experiment 3, observers who first practiced classifying color centers or boundaries as such later classified category centers faster than boundaries. A subsidiary experiment showed that this differential was not selective to particular response category labels. Neither Experiment 2 nor Experiment 3 showed any differential effect of visual field of presentation. The advantage of category center or simple over boundary or complex sensations in chromatic information processing is discussed in terms of the physiological sensitivity of the visual system to color.     

The magnitude of binocular disparity modulates search time for targets defined by a conjunction of depth and colour

Nakayama and Silverman (1986) proposed that, when searching for a target defined by a conjunction of color and stereoscopic depth, observers partition 3D space into separate depth planes and then rapidly search each such plane in turn, thereby turning a conjunctive search into a "feature" search. In their study, they found, consistent with their hypothesis, shallow search slopes when searching depth planes separated by large binocular disparities. Here, the authors investigated whether the search slope depends upon the extent of the stereoscopically induced separation between the planes to be searched (i.e., upon the magnitude of the binocular disparity. The obtained slope shows that (1) a rapid search only occurs with disparities greater than 6 min of arc, a value that vastly exceeds the stereo threshold, and that (2) the steepness of this slope increases in a major way at lower disparities. The ability to implement the search mode envisaged by Nakayama and Silverman is thus clearly limited to large disparities; less efficient search strategies are mandated by lower disparity values, as under such conditions items from one depth plane may be more likely to "intrude" upon the other. (PsycINFO Database Record (c) 2008 APA, all rights reserved).     

What are the shapes of response time distributions in visual search?

Many visual search experiments measure response time (RT) as their primary dependent variable. Analyses typically focus on mean (or median) RT. However, given enough data, the RT distribution can be a rich source of information. For this paper, we collected about 500 trials per cell per observer for both target-present and target-absent displays in each of three classic search tasks: feature search, with the target defined by color; conjunction search, with the target defined by both color and orientation; and spatial configuration search for a 2 among distractor 5s. This large data set allows us to characterize the RT distributions in detail. We present the raw RT distributions and fit several psychologically motivated functions (ex-Gaussian, ex-Wald, Gamma, and Weibull) to the data. We analyze and interpret parameter trends from these four functions within the context of theories of visual search.     

Attention-based texture segregation

Luminance- or color-defined +/- 45 degrees-oriented bars were arranged to yield single-feature or double-conjunction texture pairs. In the former, the global edge between two regions is formed by differences in one attribute (orientation, or color, or luminance). In the color/orientation double-conjunction pair, one region has +45 degrees red and -45 degrees green textels, the other -45 degrees red and +45 degrees green textels (the luminance/orientation double-conjunction pair is similar); such a pair contains a single-feature orientation edge in the subset of red (or green) textels, and a color edge in the subset of +45 degrees (or -45 degrees) textels. We studied whether edge detection improved when observers were instructed to attend to such subsets. Two groups of observers participated: in the test group, the stimulus construction was explained to observers, and they were cued to attend to one subset. The control group ran through the same total number of sessions without explanations/cues. The effect of cuing was week but statistically significant. Feature cuing was more effective for color/orientation than for luminance/orientation conjunctions. Within each stimulus category, performance was nearly the same no matter which subset was attended to. On average, a global performance improvement occurred over time even without cuing, but some observers did not improve with either cuing or practice. We discuss these results in the context of one-versus two-stage segregation theories, as well as by reference to signal enhancement versus noise suppression. We conclude that texture segregation can be improved by attentional strategies aimed to isolate specific stimulus features.     

Sex differences in color preferences transcend extreme differences in culture and ecology

At first glance, color preferences might seem to be the most subjective and context-dependent aspects of color cognition. Yet they are not. The present study compares color preferences of women and men from an industrialized and a remote, nonindustrialized culture. In particular, we investigated preferences in observers from Poland and from the Yali in Papua, respectively. Not surprisingly, we found that color preferences clearly differed between the two communities and also between sexes. However, despite the pronounced cultural differences, the way in which men and women differed from each other was almost the same in both cultures. At the same time, this sexual contrast was not specific to biological components of color vision. Our results reveal a pattern of sexual dimorphism that transcends extreme differences in culture and ecology. They point toward strong cross-cultural constraints beyond the biological predispositions of nature and the cultural particularities of nurture.     

Reaction time measures in deception research: Comparing the effects of irrelevant and relevant stimulus–response compatibility

Evidence regarding the validity of reaction time (RT) measures in deception research is mixed. One possible reason for this inconsistency is that structurally different RT paradigms have been used. The aim of this study was to experimentally investigate whether structural differences between RT tasks are related to how effective those tasks are for capturing deception. We achieved this aim by comparing the effectiveness of relevant and irrelevant stimulus–response compatibility (SRC) tasks. We also investigated whether an intended but not yet completed mock crime could be assessed with both tasks. Results showed (1) a larger compatibility effect in the relevant SRC task compared to the irrelevant SRC task, (2) for both the completed and the intended crime. These results were replicated in a second experiment in which a semantic feature (instead of color) was used as critical response feature in the irrelevant SRC task. The findings support the idea that a structural analysis of deception tasks helps to identify RT measures that produce robust group effects, and that strong compatibility effects for both enacted crimes as well as merely intended crimes can be found with RT measures that are based on the manipulation of relevant SRC.     

Top-down contingent capture by color: evidence from RT distribution analyses in a manual choice reaction task

According to the contingent capture hypothesis, observers can specify their control settings in advance of the target’s presentation to quickly attend to relevant target colors. Two predictions were derived from this hypothesis and tested in a manual choice response task. First, contingent capture by color was expected: capture of spatial attention by a better-matching color stimulus should be stronger than capture by a less-matching color stimulus. Second, with the control settings specified in advance, the contingent capture by color should commence early after the stimulus onset and should be evident among fast correct responses in an RT distribution. Both predictions are shown to hold true in two experiments. Results are discussed in light of contrasting evidence for saccadic instead of manual responses.     

Color constancy: phenomenal or projective?

Naive observers viewed a sequence of colored Mondrian patterns, simulated on a color monitor. Each pattern was presented twice in succession, first under one daylight illuminant with a correlated color temperature of either 16,000 or 4000 K and then under the other, to test for color constancy. The observers compared the central square of the pattern across illuminants, either rating it for sameness of material appearance or sameness of hue and saturation or judging an objective property-that is, whether its change of color originated from a change in material or only from a change in illumination. Average color constancy indices were high for material appearance ratings and binary judgments of origin and low for hue-saturation ratings. Individuals' performance varied, but judgments of material and of hue and saturation remained demarcated. Observers seem able to separate phenomenal percepts from their ontological projections of mental appearance onto physical phenomena; thus, even when a chromatic change alters perceived hue and saturation, observers can reliably infer the cause, the constancy of the underlying surface spectral reflectance.     

Hold the future,let the past go: Attention prefers the features of future targets

Previous studies have shown that attention can be captured by task-irrelevant distractors under the guidance of attentional control settings. However, it is unknown whether people can establish an attentional control setting (ACS) for a sequence of distinct events. The present study tested that question by asking observers to expect a sequence of two colored targets in a specific order. The results show that irrelevant distractors that matched either the color of the first expected target or that of the second target captured attention. Thus observers are unable to temporarily suppress the color of the future target in their ACS. However, the temporal order of targets is still useful for guiding attention: Observers were able to abandon the color of the first target and maintain an ACS for the second one as long as there was a sufficient time interval between the two targets.     

The nature of altered vision near the hands: Evidence for the magnocellular enhancement account from object correspondence through occlusion

A growing body of evidence indicates that the perception of visual stimuli is altered when they occur near the observer’s hands, relative to other locations in space (see Brockmole, Davoli, Abrams, & Witt, 2013, for a review). Several accounts have been offered to explain the pattern of performance across different tasks. These have typically focused on attentional explanations (attentional prioritization and detailed attentional evaluation of stimuli in near-hand space), but more recently, it has been suggested that near-hand space enjoys enhanced magnocellular (M) input. Here we differentiate between the attentional and M-cell accounts, via a task that probes the roles of position consistency and color consistency in determining dynamic object correspondence through occlusion. We found that placing the hands near the visual display made observers use only position consistency, and not color, in determining object correspondence through occlusion, which is consistent with the fact that M cells are relatively insensitive to color. In contrast, placing observers’ hands far from the stimuli allowed both color and position contribute. This provides evidence in favor of the M-cell enhancement account of altered vision near the hands.