Visual attention and perceptual grouping

Perceptual organization is thought to involve an analysis of bothtextural discontinuities andperceptual grouping. In earlier work, we found that textural discontinuities were detected normally even when visual attention was engaged elsewhere. Here we report how perceptual grouping is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of similarity. Four tasks were investigated, some requiring the observer to discriminate between horizontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identification task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of grouping performance in each case. No performance reduction was observed when either form identification or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual attention, whereas the detection of a textural discontinuity does not.     

Perceptual scaling of synthesized musical timbres: Common dimensions,specificities, and latent subject classes

To study the perceptual structure of musical timbre and the effects of musical training, timbral dissimilarities of synthesized instrument sounds were rated by professional musicians, amateur musicians, and nonmusicians. The data were analyzed with an extended version of the multidimensional scaling algorithm CLASCAL (Winsberg & De Soete, 1993), which estimates the number of latent classes of subjects, the coordinates of each timbre on common Euclidean dimensions, a specificity value of unique attributes for each timbre, and a separate weight for each latent class on each of the common dimensions and the set of specificities. Five latent classes were found for a three-dimensional spatial model with specificities. Common dimensions were quantified psychophysically in terms of log-rise time, spectral centroid, and degree of spectral variation. The results further suggest that musical timbres possess specific attributes not accounted for by these shared perceptual dimensions. Weight patterns indicate that perceptual salience of dimensions and specificities varied across classes. A comparison of class structure with biographical factors associated with degree of musical training and activity was not clearly related to the class structure, though musicians gave more precise and coherent judgments than did nonmusicians or amateurs. The model with latent classes and specificities gave a better fit to the data and made the acoustic correlates of the common dimensions more interpretable.     

When do irrelevant visual stimuli impair processing of identical targets?

Three experiments investigated whether the repeated-letter inferiority effect (RLIE) and repetition blindness (RB) are identical phenomena or not and how the RLIE can be reconciled with the flanker compatibility effect (FCE). Participants reported a masked target and ignored an unmasked distractor. We manipulated the type of distractor (identical, alternative target, or neutral), the order of presenting distractor and target, and the predictability of target location. When distractors preceded the targets, distractors identical to the target always caused deficits in target processing (i.e., RB). With simultaneous presentation, identical distractors caused deficits (i.e., an RLIE) for unpredictable target locations only. Yet the RLIE was significantly smaller than RB. This result suggests that simultaneously presented stimuli are identified serially, in random order, if target position is unpredictable. As a result, RB arises only in the 50% of all trials with identical distractors in which the distractor is identified before the target. With simultaneous presentation and predictable target location, however, parallel processing of targets and distractors was possible that gave rise to an FCE in recognition accuracy. Analyses of false alarm rates revealed no evidence of significant response biases.     

Unglücklich machende Familienideale

Zusammenfassung Der Artikel konstrastiert familiäre Lebensrealitäten und familiäre Idealvorstellungen miteinander. Für Patienten, bei denen beide weit auseinander klaffen, werden Anregungen für die Dekonstruktion selbstquälerischer Familienideale in der Psychotherapie entwickelt. Als potenziell unglücklich machend werden Familienideale beschrieben, nach denen Kinder (nur) eine Familie und Familien (nur) ein Heim brauchen; dass Familien gemeinsam verbrachte Zeit, Söhne ihre Väter und überhaupt Kinder heterosexuelle Eltern bräuchten; dass Eltern einander lieben und ihre Kinder bei sich behalten sollten; dass Kinder sich von ihren Eltern ablösen sollten. Als psychotherapeutisch nützlich werden aus Familiensoziologie und systemischer Psychotherapie die Ideen der Wahlverwandtschaft, der konsensentlasteten Diskurse und der systemischen Selbstbeobachtung empfohlen, ferner als therapeutische Techniken die zirkulären Fragen, speziell Verschlimmerungsfragen und die positive Umdeutung. Die Konstruktion neuer Rituale und die Nutzung von Netzwerkressourcen stehen am Ende der Untersuchung.Überarbeitete Fassung des Eröffnungsvortrags der Lübecker Psychotherapiewoche, 17.10.1999.     

Predictive pointing movements and saccades toward a moving target

The authors investigated whether and, if so, how velocity information is used to control predictive manual pointing movements and saccades. Participants (N = 6) intercepted an occluded moving target as if it were still visible. They kept their eyes fixated while the target moved. The target traveled over a fixed distance and changed its velocity on the way. The presentation time of the final velocity was varied. Both the eye and the hand overshot the slow target and undershot the fast target, particularly when the duration of the final velocity was short. Thus, responses were biased in the direction of the target's initial velocity. The error seemed to arise because participants did not take their latency into account when aiming at the target. Instead, they strategically aimed farther ahead when the target was fast. Amplitude was also more related to the position of velocity change than to final velocity duration. Both findings suggest that target velocity is not extrapolated but that individuals add an increment to the position of velocity change.     

Personality differences in hindsight bias

Ten personality correlates of hindsight bias were tested in a study with 75 participants answering almanac-type knowledge questions. Participants showed hindsight bias when hindsight estimates were compared to foresight estimates (memory condition), when hindsight estimates were compared to foresight estimates of other participants (BS = between-subjects hypothetical condition), and when hindsight estimates were compared to foresight estimates in response to equally difficult control items (WS = within-subject hypothetical condition). The magnitude of hindsight bias in both hypothetical conditions was positively associated with the participant's field dependence and his or her tendency for favourable self-presentation (as measured by social desirability and impression management). Between-subjects hypothetical hindsight was associated with the participant's conscientiousness and need for predictability and control (as measured by a rigidity scale). In a multiple regression analysis, 39% of the variance in BS hypothetical hindsight, 24% of the variance in WS hypothetical hindsight, but no significant proportion of the variance in memory hindsight could be accounted for by personality measures. It is concluded that individual differences in hindsight bias exist and must be taken into account in a complete model of the effect.