A novel view of between-categories contrast and within-category assimilation

This research manipulated the portion of a category distribution that is misclassified by the optimal classifier and investigated the impact on assessments of category attributes. Three separate studies manipulated the direction of overlap, the extent of overlap, and the relative base rate of the comparison category. All 3 studies produced large between-categories contrast and within-category assimilation. As expected, these effects were enhanced in conditions in which the optimal classifier misclassified a larger portion of the target category. Study 4 demonstrated that intercategory overlap in the absence of overt classification does not produce contrast and assimilation. Ironically, optimizing categorization accuracy can produce highly inaccurate beliefs about category attributes.     

Acting while perceiving: assimilation precedes contrast

To explore the nature of specific interactions between concurrent perception and action, participants were asked to move one of their hands in a certain direction while simultaneously observing an independent stimulus motion of a (dis)similar direction. The kinematics of the hand trajectories revealed a form of contrast effect (CE) in that the produced directions were biased away from the perceived directions ("Experiment 1"). Specifically, the endpoints of horizontal movements were lower when having watched an upward as opposed to a downward motion. However, when participants moved under higher speed constraints and were not presented with the stimulus motion prior to initiating their movements, the CE was preceded by an assimilation effect, i.e., movements were biased toward the stimulus motion directions ("Experiment 2"). These findings extend those of related studies by showing that CEs of this type actually correspond to the second phase of a bi-phasic pattern of specific perception-action interference.     

Orientation specificity in biological motion perception

We addressed the issue of how display orientation affects the perception of biological motion. In Experiment 1, spontaneous recognition of a point-light walker improved abruptly with image-plane display rotation from inverted to upright orientation. Within a range of orientations from 180 degrees to 90 degrees, it was dramatically impeded. Using ROC analysis, we showed (Experiments 2 and 3) that despite prior familiarization with a point-light figure at all orientations, its detectability within a mask decreased with a change in orientation from upright to a range of 90 degrees-180 degrees. In Experiment 4, a priming effect in biological motion was observed only if a prime corresponded to a range of deviations from upright orientation within which the display was spontaneously recognizable. The findings indicate that display orientation nonmonotonically affects the perception of biological motion. Moreover, top-down influence on the perception of biological motion is limited by display orientation.     

Orientation specificity and spatial updating of memories for layouts

This article examines the degree to which knowledge about the body's orientation affects transformations in spatial memory and whether memories are accessed with a preferred orientation. Participants learned large paths from a single viewpoint and were later asked to make judgments of relative directions from imagined positions on the path. Experiments 1 and 2 contribute to the emerging consensus that memories for large layouts are orientation specific, suggesting that prior findings to the contrary may not have fully accounted for latencies. Experiments 2 and 3 show that knowledge of one's orientation can create a preferred direction in spatial memory that is different from the learned orientation. Results further suggest that spatial updating may not be as automatic as previously thought.     

Disconfirmed hedonic expectations produce perceptual contrast, not assimilation

In studies of hedonic ratings, contrast is the usual result when expectations about test stimuli are produced through the presentation of context stimuli, whereas assimilation is the usual result when expectations about test stimuli are produced through labeling, advertising, or the relaying of information to the subject about the test stimuli. Both procedures produce expectations that are subsequently violated, but the outcomes are different. The present studies demonstrate that both assimilation and contrast can occur even when expectations are produced by verbal labels and the degree of violation of the expectation is held constant. One factor determining whether assimilation or contrast occurs appears to be the certainty of the expectation. Expectations that convey certainty are produced by methods that lead to social influence on subjects' ratings, producing assimilation. When social influence is not a factor and subjects give judgments influenced only by the perceived hedonic value of the stimulus, contrast is the result.     

Orientation contrast effects in the rod-and-frame test

Previous research indicates that a tilted visual display is capable of inducing eye torsion and an illusion of self-tilt in objectively upright observers. These effects may contribute to performance errors on the rod-and-frame test by rotating the perceived axes of visual space toward the tilted frame. The kinesthetic-matching method was used in the present study to see whether an effect of the visual orientation contrast between red and frame sides might also contribute to rod-and-frame test performance. Observers aligned invisible hand-held rods with the visual rod at various tilts under a control condition when the frame was absent, and under experimental conditions with the frame upright or set at 45°. The frame induced matching errors in the direction away from the frame sides which were most nearly parallel to the rod. Since no rotation of apparent visual axes should occur under these conditions, the data suggest that an orientation contrast effect is involved in the rod-and-frame test.     

The perception of assimilation and brightness contrast as derived from code theory

It is shown that assimilation and brightness contrast effects are evoked by structural aspects of patterns. In a pilot experiment, variously shaped gray patterns were used as stimuli. The backgrounds used with each of these shapes were identical: half black and half white. If the gray area against the black part was judged to be more black than the gray area against the white part, an assimilation effect will have occurred; when the reverse occurred, this was called a contrast effect. The task was to rank-order the stimuli on the assimilation-contrast scale. It is argued that the two effects are due to two different interpretations, each derivable from a different code of a pattern. The simpler the contrast code is with respect to the assimilation code, the more it will be perceptually preferred. In the specification of pattern complexity, structural information theory was used. A significant correlation was discovered between the theoretical preference for the contrast interpretation and the contrast preference of subjects.     

The ups and downs of social comparison: mechanisms of assimilation and contrast

Social comparisons influence self-evaluations in multiple ways. Sometimes self-evaluations are assimilated toward a given standard. At other times, they are contrasted away from the standard. On the basis of the selective accessibility model (T. Mussweiler, 2003a), the authors hypothesized that assimilation results if judges engage in the comparison process of similarity testing and selectively focus on similarities to the standard, whereas contrast occurs if judges engage in dissimilarity testing and selectively focus on differences. If these alternative comparison mechanisms are indeed at play, then assimilative and contrastive social comparisons should be accompanied by diverging informational foci on similarities versus differences. Results of 5 studies support this reasoning, demonstrating that assimilation results under conditions that foster similarity testing, whereas contrast occurs under conditions that foster dissimilarity testing. Furthermore, assimilative social comparisons are accompanied by a general informational focus on similarities, whereas contrastive comparisons are accompanied by a focus on differences.     

Priming us and them: automatic assimilation and contrast in group attitudes

Social judgment theory holds that a person's own attitudes function as reference points, influencing the perception of others' attitudes. The authors argue that attitudes themselves are influenced by reference points, namely, the presumed attitudes of others. Whereas exposure to a group that acts as a contextual reference should cause attitude assimilation, exposure to a group that acts as a comparative reference should cause attitude contrast. In Study 1, participants subliminally primed with their political ingroup or outgroup endorsed more extreme political positions than did controls. Study 2 demonstrated that prime types known to uniquely facilitate assimilation and contrast enhanced the polarization effect in the ingroup and outgroup conditions, respectively. Study 3 established an important boundary condition for whether group salience produces attitude assimilation or contrast by showing that perceived closeness to the elderly moderates the direction and strength of the group priming effect. The results suggest that the transition from assimilation to contrast occurs when a group ceases to function as a context and becomes a comparison point. Implications for social judgment theory, assimilation and contrast research, and conflict escalation are discussed.     

Awareness of the influence as a determinant of assimilation versus contrast

In the present study, subjects had to generate an evaluative judgment about a target person on the basis of his behaviour that had both positive and negative implications. In a previous phase of the study that was ostensibly unrelated to the judgment task, the relevant trait categories were primed. Subsequently, half of the subjects were reminded of the priming episode. Consistent with earlier research (e.g. Lombardi, Higgins and Bargh, 1987; Newman and Uleman, 1990) that used memory of the priming events as a correlational measure, a contrast effect was found under the ‘reminding’ condition and assimilation resulted when subjects were not reminded of the priming episode. This pattern of results is interpreted as the consequence of corrective influences.     

The time-based word length effect and stimulus set specificity

The word length effect is the finding that short items are remembered better than long items on immediate serial recall tests. The time-based word length effect refers to this finding when the lists comprise items that vary only in pronunciation time. Three experiments compared recall of three different sets of disyllabic words that differed systematically only in spoken duration. One set showed a word length effect, one set showed no effect of word length, and the third showed a reverse word length effect, with long words recalled better than short. A new fourth set of words was created, and it also failed to yield a time-based word length effect. Because all four experiments used the same methodology and varied only the stimulus sets, it is argued that the time-based word length effect is not robust and as such poses problems for models based on the phonological loop.     

The syllable-based word length effect and stimulus set specificity

The word length effect is the finding that a list of items that take less time to pronounce is better recalled on an immediate serial recall test than an otherwise equivalent list of items that take more time to pronounce. Contrary to the predictions of all major models of the word length effect, Hulme, Suprenant, Bireta, Stuart, and Neath (2004) found that short and long items presented within the same list were recalled equally as well as short items presented in lists of just short items. Different results were reported by Cowan, Baddeley, Elliot, and Norris (2003), who found that mixed lists were recalled worse than pure short lists, but better than pure long lists. The experiments reported here suggest that the different empirical findings are due to properties of the stimulus sets used: one stimulus set produces results that replicate Cowan et al., whereas all other sets tested so far yield results that replicate Hulme et al.     

Attention,brightness contrast,and assimilation: The influence of relative area

A model of information transmission in the visual system which describes the effect of attention on apparent brightness is examined. This model states in part that the luminance of the portion of the visual field which captures the attention is overweighted in arriving at an overall average luminance level across the visual field. As this average must be computed with respect to both luminance and relative area, it is hypothesized that increasing the relative area of the portion of the visual field that captures the attention will result in a greater effect on the apparent brightness of all parts of the visual field. Two predictions, which involve the effect of relative area on apparent brightness, are experimentally tested and confirmed.