Spatial frequency content of visual imagery

Three experiments employing the McCollough paradigm were conducted to determine the spatial-frequency content of visual imagery. In Experiment 1, large and reliable pattern-contingent color aftereffects were obtained after adaptation to visual imagery. The direction of the aftereffects indicated that subjects were adapting to higher spatial frequencies in their imagery. These results contrast with the data of Experiment 2, which demonstrate that color aftereffects obtained with adaptation to physically present stimuli are mediated by the fundamental spatial frequency components. The magnitude of the imagery-induced aftereffects in Experiment 1 equaled the magnitude of the externally induced aftereffects obtained in Experiment 2 with the same subjects. By blurring the to-be-imaged patterns (Experiment 3), the fundamental Fourier components became the salient perceptual features of the stimuli, and the direction of the imagery-induced aftereffects was reversed from that of Experiment 1, indicating that the spatial frequency content of the imagery had changed from higher to lower frequencies. Under normal viewing conditions, subjects use the higher spatial frequencies associated with the perceptually salient edges of stimuli to construct their images. The results of Experiments 1 and 3 are discussed in light of a current controversy over the nature of information representation in imagery, and it is concluded that support has been obtained for the analog model of visual imagery.     

Computer graphic studies of the role of facial similarity in judgements of attractiveness

Anecdotally, spouses are often said to resemble one another. This study investigates the effects of similarity between participants and stimuli on judgements of facial attractiveness: does “like prefer like”? Using computer graphic techniques, opposite sex facial stimuli were generated from subjects' photographs. Experiment 1 showed a correlation between attractiveness and similarity but the effect can be explained by the attractiveness of average faces. Beyond this, there was a trend for individual subjects to rate opposite sex images with a similar face shape to their own face as more attractive than other subjects. Experiment 2 allowed subjects to interactively manipulate an opposite sex facial image along a continuum from a self-similar shape, through an average face shape, to a face with opposite characteristics. No significant preferences for self-similar or opposite characteristics were found. Preferences for average faces are stronger than preferences for self-similar faces.     

Computer graphic studies of the role of facial similarity in judgements of attractiveness

Anecdotally, spouses are often said to resemble one another. This study investigates the effects of similarity between participants and stimuli on judgements of facial attractiveness: does “like prefer like”? Using computer graphic techniques, opposite sex facial stimuli were generated from subjects' photographs. Experiment 1 showed a correlation between attractiveness and similarity but the effect can be explained by the attractiveness of average faces. Beyond this, there was a trend for individual subjects to rate opposite sex images with a similar face shape to their own face as more attractive than other subjects. Experiment 2 allowed subjects to interactively manipulate an opposite sex facial image along a continuum from a self-similar shape, through an average face shape, to a face with opposite characteristics. No significant preferences for self-similar or opposite characteristics were found. Preferences for average faces are stronger than preferences for self-similar faces.     

Constitutional biases in early perceptual learning: I. Preferences between colors, patterns, and composite stimuli of colors and patterns in genetically manipulated and imprinted quail chicks (C. coturnix japonica)

Bidirectional genetic selection of quail for early color preferences, for eighteen generations, resulted in nearly perfect choices of blue over red in one and red over blue in the other selected line. It also enhanced the preference of a grated over a dotted black-and-white pattern. Color and pattern preferences in hybrids of selected and control lines fell back to about halfway between parental values. Choices between composite stimuli of colors and patterns indicated summation of the respective, genetically influenced preference values, with partial dominance of color over pattern effects. Exposure to colors modified color choices. Exposure to colored patterns likewise modified color choices, but it did not change, or only marginally changed, choices between patterns. The phenotypic expression of this selective learning, however, was influenced by the genetically manipulated preference values and preference combinations of colors and patterns in the stimuli with which postexposure performances were tested. Overall, the data highlighted the need for concepts that would discriminate between the developmental and the episodic expression of genetic influences and genotype--environment interactions in behavior.     

Categorical shape and color coding by pigeons

Categorical coding is the tendency to respond similarly to discriminated stimuli. Past research indicates that pigeons can categorize colors according to at least three spectral regions. Two present experiments assessed the categorical coding of shapes and the existence of a higher order color category (all colors). Pigeons were trained on two independent tasks (matching-to-sample, and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials one of the two comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the two stimuli from the other task was introduced suggested categorical coding rules. In Experiment 1 evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Experiment 2 replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Overall, the results indicate that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical.     

Eye scanpaths during visual imagery reenact those of perception of the same visual scene

Eye movements during mental imagery are not epiphenomenal but assist the process of image generation. Commands to the eyes for each fixation are stored along with the visual representation and are used as spatial index in a motor‐based coordinate system for the proper arrangement of parts of an image. In two experiments, subjects viewed an irregular checkerboard or color pictures of fish and were subsequently asked to form mental images of these stimuli while keeping their eyes open. During the perceptual phase, a group of subjects was requested to maintain fixation onto the screen's center, whereas another group was free to inspect the stimuli. During the imagery phase, all of these subjects were free to move their eyes. A third group of subjects (in Experiment 2) was free to explore the pattern but was requested to maintain central fixation during imagery. For subjects free to explore the pattern, the percentage of time spent fixating a specific location during perception was highly correlated with the time spent on the same (empty) locations during imagery. The order of scanning of these locations during imagery was correlated to the original order during perception. The strength of relatedness of these scanpaths and the vividness of each image predicted performance accuracy. Subjects who fixed their gaze centrally during perception did the same spontaneously during imagery. Subjects free to explore during perception, but maintaining central fixation during imagery, showed decreased ability to recall the pattern. We conclude that the eye scanpaths during visual imagery reenact those of perception of the same visual scene and that they play a functional role.     

Color preference in pigeons: stimulus intensity and reinforcement contingency effects in the avoidance of blue stimuli.

In a procedure intended to determine color preference in pigeons (which partially replicated Catania, Owens, & von Lossberg, 1983), two keys were illuminated by different colors drawn from a set of amber, red, green, or blue stimuli; this was followed by the presentation of grain when either of the two colors was pecked. The grain was illuminated alternately across trials with the colors presented on the keys. In Experiment 1 the intensity of the color stimuli used was not equalized, whereas in Experiment 2 the intensity of the colors was equalized. The low preference for blue found in Experiment 1, as measured by differential key pecking, was not found in Experiment 2. The discriminability of the intensity-equalized colors was confirmed in Experiment 2a, in which equal-intensity color discrimination problems were presented. In Experiment 3, as in Catania et al. (1983), a response-independent reinforcement schedule was used, but with intensity-equalized colors. In contrast to Experiment 2, very low preference for blue was found here and in Experiment 4, which used a within-subject procedure. These findings suggest that pigeon color preference may be a function of intensity, but all controlling variables have not as yet been identified.     

The Impact of Stimuli Color in Lexical Decision and Semantic Word Categorization Tasks

In two experiments, we examined the impact of color on cognitive performance by asking participants to categorize stimuli presented in three different colors: red, green, and gray (baseline). Participants were either asked to categorize the meaning of words as related to the concepts of “go” or “stop” (Experiment 1) or to indicate if a neutral verbal stimulus was a word or not (lexical decision task, Experiment 2). Overall, we observed performance facilitation in response to go stimuli presented in green (vs. red or gray) and performance inhibition in response to go stimuli presented in red. The opposite pattern was observed for stop‐related stimuli. Importantly, results also indicated that color might also be used to categorize neutral stimuli. Overall, these findings provide support to the green‐go and red‐stop color associations and test the potential functional autonomy acquired by these colors and the boundary conditions to their effects on stimuli categorization.     

DOES CONDITIONAL DISCRIMINATION LEARNING BY PIGEONS NECESSARILY INVOLVE HIERARCHICAL RELATIONSHIPS?

Four experiments demonstrate that when putative conditional and discriminative cues are presented simultaneously in the single reversal procedure, it is not possible to ascribe a uniquely conditional or uniquely discriminative function to either of the cues. In Experiment 1, pigeons were trained to respond to a blue key and not to a red key while the houselight was on; then in a different session they learned the reversal of this discrimination with the houselight off (single reversal). Separate groups were tested for color generalization with houselight conditions alternating in blocks of trials or for houselight intensity generalization with blue and red key colors alternating in blocks of trials. Both test procedures revealed a conditional relationship between houselight and key color conditions. Experiment 2 produced the same result following training in which the key colors were held constant across training sessions while the houselight and no houselight conditions varied within sessions. In Experiment 3, separate groups were trained with the two procedures but were tested with randomly ordered combinations of key colors and houselight intensities. The two groups yielded indistinguishable bidimensional generalization gradients with peaks at both previously reinforced stimulus combinations. In Experiment 4 the subjects were switched from one of these training procedures to the other with no decrement in their discriminative performance. We conclude that for successive discriminations between conditional- and discriminative-stimulus combinations, the notion of a hierarchical relation between conditional and discriminative stimuli must be extended to include a symmetrical relationship or the notion should be abandoned altogether.     

Color preferences, extraversion, and neuroticism of art students.

Color preferences of 190 art students (G?tz & G?tz, 1974, 1975) were compared with the corresponding scores on extraversion (E) and neuroticism (N). It was found that the preferences of a group of 27 highly gifted young artists were different from preferences of average and less gifted Ss who had little or no artistic practice. In the latter group extraverts and ambiverts mainly preferred primary and secondary colors (light clear and dark clear tones included), while introverts preferred tertiary colors (earth colors) and achromatics. However, in the group of highly gifted Ss no significant differences between positive and negative rankings in both color categories were found. Neuroticism had no effect on color preferences; this holds for introverts and extraverts and for each single color.     

How chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) perform in a modified emotional Stroop task

The emotional Stroop task is an experimental paradigm developed to study the relationship between emotion and cognition. Human participants required to identify the color of words typically respond more slowly to negative than to neutral words (emotional Stroop effect). Here we investigated whether chimpanzees (Pan troglodytes) would show a comparable effect. Using a touch screen, eight chimpanzees were trained to choose between two simultaneously presented stimuli based on color (two identical images with differently colored frames). In Experiment 1, the images within the color frames were shapes that were either of the same color as the surrounding frame or of the alternative color. Subjects made fewer errors and responded faster when shapes were of the same color as the frame surrounding them than when they were not, evidencing that embedded images affected target selection. Experiment 2, a modified version of the emotional Stroop task, presented subjects with four different categories of novel images: three categories of pictures of humans (veterinarian, caretaker, and stranger), and control stimuli showing a white square. Because visits by the veterinarian that include anaesthetization can be stressful for subjects, we expected impaired performance in trials presenting images of the veterinarian. For the first session, we found correct responses to be indeed slower in trials of this category. This effect was more pronounced for subjects whose last anaesthetization experience was more recent, indicating that emotional valence caused the slowdown. We propose our modified emotional Stroop task as a simple method to explore which emotional stimuli affect cognitive performance in nonhuman primates.     

Color preferences in gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes)

Color plays an important biological role in the lives of many animals, with some species exhibiting preferences for certain colors over others. This study explored the color preferences of two species of ape, which, like humans, possess trichromatic color vision. Six western lowland gorillas, and six chimpanzees, housed in Belfast Zoological Gardens, were exposed to three stimuli (cloths, boxes, sheets of acetate) in red, blue, and green. Six stimuli of the same nature, in each of the three colors, were provided to both species for 5 days per stimulus. The amount of interest that the animals showed toward each stimulus of each color was recorded for 1 hr. Results showed that the apes, both when analyzed as two separate groups, and when assessed collectively, showed significant color preferences, paying significantly less attention to the red-, than to the blue- or green-colored stimuli. The animals' interest in the blue- and green-colored stimuli did not differ significantly. Overall, the findings suggest that gorillas and chimpanzees, our closest living relatives, may harbor color preferences comparable to those of humans and other species.     

Hedonic contrast and condensation: Good stimuli make mediocre stimuli less good and less different

Loud sounds make soft sounds softer (contrast) and also make them less discriminable (which we callcondensation). We report on parallel phenomena in hedonics: Good stimuli reduce the pleasantness of less good stimuli, and also reduce people’s preferences among the less good stimuli. In Experiment 1, subjects rated the pleasantness of fruit juices diluted to approximate hedonic neutrality. Subjects who had just previously drunk and rated some good-tasting full-strength juices rated the diluted juices lower than did subjects who had not (hedonic contrast). In Experiment 2, subjects drank pairs of diluted juices and rated their preference for one juice over the other. Subjects who had just previously drunk and rated pairs of full-strength juices gave lower preference ratings between the diluted juices than did subjects who had not (condensation). Thus the same stimulus set produced contrast in Experiment 1 and condensation in Experiment 2, paralleling results in loudness.     

Discrimination of color and pattern novelty in one-month human infants

Visual discrimination of novel colors and patterns by one-month infants was studied in two experiments where visual reinforcers were presented contingent upon infants' rate of nonnutritive, high-amplitude sucking. Discrimination was measured by recovery of sucking to the presentation of novel visual reinforcing stimuli following decrements in sucking to familiar visual stimuli. In Expt 1, following decrement to familiar stimuli, independent groups received either a change in color, pattern, both color and pattern, or no stimulus change. Reliable recovery was demonstrated for the three stimulus novelty groups relative to the no-change control. Experiment 2, employing achromatic visual reinforcers also showed reliable recovery to pattern change relative to no-change controls. These findings with one-month infants indicate discrimination between familiar and novel visual reinforcers on the basis of color and pattern differences and an increase due to novelty in the reinforcing effectiveness of visual stimuli. Individual subject differences in response decrement magnitude during familiarization were positively correlated with amount of response recovery to novelty.     

Verbal coding and the elimination of Stroop interference in a matching task

Translational models of the Stroop effect (Virzi & Egeth, 1985) predict that Stroop interference can be eliminated if subjects can be induced to process target colors using a coding system separate from the coding system used to process distractors. This hypothesis was tested in two experiments. In the first experiment, we attempted to eliminate the need for subjects to translate target colors to verbal codes when responding to Stroop stimuli. Before responding to verbal incongruent color word distractors, subjects practiced matching colors to irregular shapes. It was expected that subjects would use nonverbal codes to mediate responding in this task. After practice, subjects continued the matching task in the presence of incongruent color words. Stroop interference persisted, contrary to predictions. Because subjects reported adopting verbal strategies to perform the matching task, Experiment 2 was designed to control the verbal coding strategies that subjects employed. Before responding to Stroop distractor stimuli, subjects in the nonsense name group practiced using nonsense names to mediate the matching of shapes to colors; subjects in the actual name group used actual color names to mediate performance in the matching task. When incongruent color word distractors were introduced, Stroop interference was eliminated for subjects in the nonsense name group, but persisted for subjects in the actual name group. The results are interpreted as consistent with an outcome conflict (Navon & Miller, 1987) or a modified translational model of the Stroop effect.     

Imagery ability and the identification of hands: A chronometric analysis

In a replication of Cooper and Shepard's (1975) study of hand recognition, it was found that individual differences in imagery ability had a significant influence on reaction times to such stimuli (Experiment 1). However, it was found (Experiment 2) that individual difference effects were only seen if prior instructions to use imagery were given to the subjects.     

Ecological Effects in Cross‐Cultural Differences Between U.S. and Japanese Color Preferences

We investigated cultural differences between U.S. and Japanese color preferences and the ecological factors that might influence them. Japanese and U.S. color preferences have both similarities (e.g., peaks around blue, troughs around dark‐yellow, and preferences for saturated colors) and differences (Japanese participants like darker colors less than U.S. participants do). Complex gender differences were also evident that did not conform to previously reported effects. Palmer and Schloss's (2010) weighted affective valence estimate (WAVE) procedure was used to test the Ecological Valence Theory's (EVT's) prediction that within‐culture WAVE‐preference correlations should be higher than between‐culture WAVE‐preference correlations. The results supported several, but not all, predictions. In the second experiment, we tested color preferences of Japanese–U.S. multicultural participants who could read and speak both Japanese and English. Multicultural color preferences were intermediate between U.S. and Japanese preferences, consistent with the hypothesis that culturally specific personal experiences during one's lifetime influence color preferences.     

Comparing color-word and picture-word Stroop-like effects: A test of the Glaser and Glaser (1989) model

Summary Glaser and Glaser (1989) assume that the processing of colors and pictures is highly similar in that, compared to words, both kinds of stimulis have privileged access to semantic information. This assumption was tested in the present research. In Experiment 1, the season corresponding to the color or to the word of color-word Stroop stimuli had to be named (e.g., green for spring). In Experiment 2, subjects had to name the season corresponding to the picture or the word of a picture-word stimulus (e. g., flower for spring). According to Glaser and Glaser (1989), privileged semantic processing of colors and pictures should be evidenced by a larger interfering power of color and picture distractors than of word distractors. However, the asymmetric pattern of interference was observed only with picture-word stimuli (Experiment 2), but not with color-word stimuli (Experiment 1), suggesting that, unlike pictures, colors do not have privileged access to semantic information. It was also found that word distractors interfered with the semantic processing of pictures, a result that is incompatible with the dominance rule postulated by Glaser and Glaser (1989). From these results, an adapted version of the Glaser and Glaser model is proposed: colors are assumed to have privileged access to a separate color processing system and the pattern of interference depends upon the relative activation strength of the response alternatives activated by the target and the distractor.     

Seasonal Variations in Color Preference

We investigated how color preferences vary according to season and whether those changes could be explained by the ecological valence theory (EVT). To do so, we assessed the same participants’ preferences for the same colors during fall, winter, spring, and summer in the northeastern United States, where there are large seasonal changes in environmental colors. Seasonal differences were most pronounced between fall and the other three seasons. Participants liked fall‐associated dark‐warm colors—for example, dark‐red, dark‐orange (brown), dark‐yellow (olive), and dark‐chartreuse—more during fall than other seasons. The EVT could explain these changes with a modified version of Palmer and Schloss’ (2010) weighted affective valence estimate (WAVE) procedure that added an activation term to the WAVE equation. The results indicate that color preferences change according to season, as color‐associated objects become more/less activated in the observer. These seasonal changes in color preferences could not be characterized by overall shifts in weights along cone‐contrast axes.