Knowledge that Transforms

The Poggendorff illusion is one of the most prominent geometrical-optical illusions and has attracted enduring interest for more than a hundred years. Most modern theories explain the illusion by postulating various kinds of distortion of the “test” component of the figure by the context or the inducing component. They make no reference to the importance of processes involved in three-dimensional scene perception for understanding the illusion. We measured the strength of the Poggendorff illusion in configurations containing solid inducing surfaces as opposed to the usual parallel lines. The surface, oblique-line, and background luminances were manipulated separately to create configurations consistent with modal completion of the obliques in front of the surface. The marked decrease in the size of the illusion in conditions favoring modal completion is consistent with claims that perceived spatial layout is a major determinant of the Poggendorff illusion.

A professor of history at The Hebrew University noted that his students were often surprised to learn that some event in America happened at about the same time as another in Europe, because the American event seemed to them to have happened more recently. We confirmed the validity, of this anecdotal observation experimentally, and offer an explanation. We discuss how this bias may be an effect of judgment, rather than memory. We then show experimentally that students like those who demonstrated the bias regarded America as the New World, as opposed to Europe's Old World. Our theoretical account, based on judgment by representativeness, posits that if one category is deemed more X than another (e.g., American history is deemed more "recent" than European history), then its members will be judged more X than members of the other, ceteris paribus. Hence, an American historical event will appear more recent than a contemporaneous European event.

Considerable evidence indicates that people overattribute causality to a given stimulus when it is salient or the focus of their attention—the so-called illusory-causation phenomenon. Although illusory causation has proved to be quite robust and generalizable, a compelling explanation for it has not been empirically documented. Four social-attribution studies were conducted to test the hypothesis that illusory causation occurs because salient information is initially registered, or perceptually organized, differently than nonsalient information. The results provide considerable support for the notion that people's literal point of view affects how they initially perceive, or extract, information from an observed interaction, which in turn affects their judgments regarding the causal influence exerted by each interactant.

Given evidence demonstrating that infants 3 months of age and younger can utilize the Gestalt principle of lightness similarity to group visually presented elements into organized percepts, four experiments using the familiarization/novelty-preference procedure were conducted to determine whether infants can also organize visual pattern information in accord with the Gestalt principle of form similarity. In Experiments 1 and 2, 6- to 7-month-olds, but not 3- to 4-month-olds, presented with generalization and discrimination tasks involving arrays of X and O elements responded as if they organized the elements into columns or rows based on form similarity. Experiments 3 and 4 demonstrated that the failure of the young infants to use form similarity was not due to insufficient processing time or the inability to discriminate between the individual X and O elements. The results suggest that different Gestalt principles may become functional over different time courses of development, and that not all principles are automatically deployed in the manner originally proposed by Gestalt theorists.

Working memory is a set of interactive cognitive processes that maintain information on-line and available for analysis. Part of the system is specialized for maintaining verbal information, a core component of which is thought to be a phonological store. On the basis of the study of patients with acquired brain lesions, this store has been localized to the supramarginal and angular gyri of the speech-dominant hemisphere, and some functional neuroimaging studies support this localization. However, other imaging studies localize the phonological store in a more dorsal region of the parietal lobe. To reconcile these findings, we examined the phonological-similarity effect in two different tasks. A phonological-similarity effect was observed only in the task that involved sequential presentation and explicit verbal rehearsal. We conclude that at least one possible source of the differences in brain activation between different working memory tasks may be differences in phonological processing.

When two visual targets, T1 and T2, are presented in rapid succession, detection or identification of T2 is almost universally degraded by the requirement to attend to T1 (the attentional blink, or AB). One interesting exception occurs when T1 is a brief gap in a continuous letter stream and the task is to discriminate its duration. One hypothesized explanation for this exception is that an AB is triggered only by attention to a patterned object. The results reported here eliminate this hypothesis. Duration judgments produced no AB whether the judged duration concerned a short gap in the letter stream (Experiment 1) or a letter presentedfor slightly longer than others (Experiment 2). When identification of an identical longer letter T1 was required (Experiment 3), rather than a duration judgment, the AB was reestablished Direct perceptual judgments of letter streams with gaps embedded showed that whereas brief gaps result in the percept of a single, briefly hesitating stream, longer gaps result in the percept of two separate streams with a separating pause. Correspondingly, an AB was produced in Experiment 4, when participants were required to judge the duration of longer T1 gaps. We propose that, like spatially separated objects, temporal events are parsed into discrete, hierarchically organized events. An AB is triggered only when a new attended event is defined, either when a long pause creates a new perceived stream (Experiment 4) or when attention shifts from the stream to the letter level (Experiment 3).

In mirror reflections, visual stimuli in near peripersonal space (e.g., an object in the hand) can project the retinal image of far, extrapersonal stimuli "beyond" the mirror. We studied the interaction of such visual reflections with tactile stimuli in a cross-modal congruency task. We found that visual distractors produce stronger interference on tactile judgments when placed close to the stimulated hand, but observed indirectly as distant mirror reflections, than when directly observed in equivalently distant far space, even when in contact with a dummy hand or someone else's hand in the far location. The stronger visual-tactile interference for the mirror condition implies that near stimuli seen as distant reflections in a mirror view of one's own hands can activate neural networks coding peripersonal space, because these visual stimuli are coded as having a true source near to the body.