Visual search for size-defined target objects is modulated by the Ebbinghaus apparent-size illusion: facilitatory and inhibitory effects of the context objects

Five experiments were carried out to investigate under which conditions the apparent size of objects is computed and exploited optimally in visual search for size-defined targets. Observers searched for a target test circle that was retinally larger than the distractor test circles, with both types of circles surrounded by context circles modulating the apparent size of the test circles (Ebbinghaus illusion). RTs were the faster the better test circles could be differentiated from the context circles, ie with smaller numbers of context circles, larger distances, and higher lightness (or colour) contrast between test and context circles. Apparent-size modulation had a strong influence on search RTs, resulting in faster RTs with smaller, and slower RTs with larger, context circles. A model assuming overall facilitatory effects of the apparent-size modulation and interference effects arising from decreasing test-context circle discriminability can explain the present results.     

Cross-trial priming in visual search for singleton conjunction targets: role of repeated target and distractor features

Kristjánsson, Wang, and Nakayama (2002) demonstrated that visual search for conjunctively defined targets can be substantially expedited ("primed") when target and distractor features are repeated on consecutive trials. Two experiments were conducted to examine whether the search response time (RT) facilitation on target-present trials results from repetition of target-defining features, distractor features, or both. The experiments used a multiple conjunctive search paradigm (adapted from Kristjánsson et al., 2002), in which the target and distractor features were varied (i.e., repeated) independently of each other across successive trials. The RT facilitation was numerically largest when both target and distractor features were repeated, but not significantly larger than that when only distractor features were repeated. This indicates that cross-trial priming effects in conjunctive visual search result mainly from the repetition of distractor, rather than target, features.     

Synchronous Information Presented in 40-Hz Flicker Enhances Visual Feature Binding

Recent neurophysiological studies have encouraged speculation that the synchronization of spatially distributed neural assemblies (at around 40 Hz in the neocortex) is responsible for the binding of discrete stimulus components into coherent wholes during visual object perception. Using a novel paradigm, we demonstrated specific figural priming under 40-Hz stimulus modulation conditions. Further, under these conditions, observers were not aware of the prime"s existence, nor did the prime act as a stimulus-driven attentional cue. These findings provide the first psychophysical support for a theory of preattentive coding of visual objects, based on an externally entrained and thereby synchronized 40-Hz feature-binding mechanism.     

Visual search for singleton feature targets within and across feature dimensions

Three experiments investigated visual search for singleton feature targets. The critical dimension on which the target differed from the nontargets was either known in advance or unknown—that is, the critical difference varied eitherwithin a dimension oracross dimensions. Previous work (Treisman, 1988) had shown that, while the search reaction time (RT) functions were flat in both conditions, there was an intercept cost for the cross-dimension condition. Experiment 1 examined whether this cost would disappear when responses could be based on the detection ofany (target—nontarget) difference in the display (by requiring a “heterogeneity/homogeneity” decision). The cost remained. This argues that pop-out requires (or involves) knowledge of the particular dimension in which an odd-one-out target differs from the nontargets; furthermore, that knowledge is acquired through the elimination of dimensions not containing a target. In Experiment 2, the subjects had to eliminate (or ignore) one potential source of difference in order to give a positive response (displays could contain a “noncritical” difference requiring a negative response). The result was a comparatively large cost in the within-dimension (positive) condition. This can be taken to indicate that popout as such does not make available information as to the particular feature value in which the target differs from the nontargets. Experiment 3 examined whether search priorities can be biased in accordance with advance knowledge of the likely source of difference. The subjects were found to have a high degree of top-down control over what particular dimension to assign priority of checking to. The implication of the results for models of visual search and selection are discussed.     

Medical problems,maladaptive behaviors,and the developmentally disabled

Research has shown that aberrant behaviors of people with developmental disabilities have multiple determinants; of these, medical problems and their potential relations to aberrant behaviors, have been, for the most part, not studied. This retrospective study examined the relations of 26 acute medical treatements to the aberrant behaviors of 10 elderly people with developmental disabilities. Results showed that 73.1% of the aberrant behaviors decreased in frequency after medical treatments. The study suggests the importance of acute medical problems and treatments as possible factors in the occurrence of aberrant behaviors in this population.     

Variation of the Subjective Vertical on the parallel swing at different body positions

Summary Subjects on a horizontally moving parallel swing perceive a change of the position of the body and of the Subjective Vertical (SV). The magnitude of the SV-change was recorded at different body-positions on the swing. The SV-change was smaller when the vertex-base head-axis was oriented parallel or close to parallel to swing movement than when the vertex-base head axis was oriented perpendicular to this movement. Perpendicular orientation implies either head vertex-up or head vertex-down. The results are discussed with respect to other findings on the various sensory input systems.

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Zusammenfassung Versuchspersonen auf einer horizontal schwingenden Parallel-Schaukel nehmen eine Änderung der Lage des eigenen Körpers und der Stellung der Subjektiven Vertikalen (SV) wahr. Die Größe der im Schwingrhythmus wechselnden SV-Änderung wurde bei verschiedenen Körperstellungen auf der Schaukel untersucht. Sie war kleiner, wenn die Scheitel-Basis-Achse des Kopfes in oder nahe der Schwingungsrichtung und größer, wenn sie senkrecht oder nahezu senkrecht dazu stand; die senkrechte Stellung konnte entweder Scheitel-aufwärts oder Scheitel-abwärts sein. Die Ergebnisse werden im Zusammenhang mit anderen Befunden über die beteiligten sensorischen Systeme diskutiert.

     

Lexical representation of fact and opinion

This research investigated the lexical properties underlying comprehension that a word represents fact or opinion. In Experiment 1 subjects reliably identified words as either fact or opinion. Bivariate correlations and multiple regression showed that fact/opinion judgments were predicted primarily by ratings of the ease of verifiability of a word's referent and secondarily by the word's literalness, but not by several other lexical attributes: abstractness-concreteness, vagueness-preciseness, and evaluation. Experiment 2 extended the results of the first experiment to an implicit fact/opinion judgment, i.e., the identification of headlines as originating from a newspaper's front page (presumably based primarily upon fact) or from the editorial page (presumably based upon opinion). The headline judgments, also made reliably by subjects, were predicted by the same variables found significant in the first experiment, i.e., by verifiability and literalness, but not by the other lexical properties. Thus, the results of both experiments indicate that the identification of a word as representing fact or opinion is rooted in a word's verifiability and literalness.