Knowledge that Transforms

Viewers were presented with a rapid sequence of very brief stimulus pairs, each of which consisted of a pictured object followed by a related or unrelated word. The form of relatedness between the picture and word was manipulated across experiments (identical concept, associated concept, ink color of the picture). Recognition memory for the pictures was affected not only by whether or not paired items were conceptually identical or semantically related, but also by whether or not the words named an irrelevant feature, ink color. These results show that sequential items are integrated on the basis of similarity at whatever level is available, so that the stability of the memory representation of one or both items is increased. We propose that a common mechanism may underlie integration, priming, and selective attention.

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.

Superconditioning is said to occur when learning an association between a conditioned stimulus (CS) and unconditioned stimulus (US) isfacilitated by pairing the CS with the US in the presence of a previously established conditioned inhibitor. Previous demonstrations of superconditioning have been criticized because their control conditions have allowed alternative interpretations. Using a within-subjects autoshaping procedure, the present study unambiguously demonstrated superconditioning. The results support the view that super-conditioning is the symmetric opposite of blocking.

Reading-disabled children often have accompanying deficits in motor coordination. Rather than assuming impairment of a shared neural mechanism, we conjecture that coordination difficulties that undermine normal speech would also undermine development of phonological awareness, which is necessary for reading fluency. Nonimpaired readers who vary in fluency, therefore, should also covary in coordination. Reliable interrelationships between phonological decoding skills and the speed and variability of sequentially tapping the fingers of one hand (either dominant or nondominant) were, indeed, found for college undergraduates. Reading measures that do not emphasize phonological decoding did not show the same connection. Characterizing phonological decoding as a skill and the long-term consequences of failure to master that skill suggest that it could benefit from practice even in high-literacy populations.

One hallmark of vision in adults is the dichotomy between color and motion processing. Specifically, areas of the brain that encode an object's direction of motion are thought to receive little information about object color We investigated the development of this dichotomy by conducting psychophysical experiments with human subjects (2-, 3-, and 4-month-olds and adults), using a novel red-green stimulus that isolates color-based input to motion processing. When performance on this red-green motion stimulus was quantified with respect to performance on a luminance (yellow-black) standard, we found stronger color-based motion processing in infants than in adults. These results suggest that color input to motion areas is greater early in life, and that motion areas then specialize to the adultlike state by reweighting or selectively pruning their inputs over the course of development.

The present article provides evidence for the role of participants' familiarity with units of measurement in categorical accentuation with unidimensional physical estimates. Belgian and American participants estimated the lengths of lines varying in length. Depending on the condition, the lines were or were not systematically associated with categorical labels, and the estimates were made either in inches or in centimeters. Consistent with our predictions, (a) categorical accentuation was higher when the lines were systematically categorized than when they were not, and (b) this effect was stronger when participants reported their estimates in an unfamiliar measurement unit (i.e., Belgian participants using inches, and American participants using centimeters). These findings support the view that people's reliance on categorical information is more likely to emerge given uncertain contexts of judgment. Additionally, they may help explain why researchers have had difficulties replicating the categorical accentuation effect in the past.

Perceived occlusion of aligned T-junctions and subjective contours at implicit T-junctions are often assumed to be related but are rarely examined with respect to common mechanisms. Using the method of paired comparison, we measured the strength of perceived occlusion at explicit T-junctions and the strength of subjective contours at implicit T-junctions (using different subjects) along the aligned edges of eight sets of inducer shapes. Sets varied in the similarity of component shapes with respect to orientation, height, width, and color With increasing shape similarity there was a striking decrease in both the strength of subjective contours and the strength of perceived occlusion; the correlation between these two kinds of judgments was .97. We conclude that common mechanisms underlie these two percepts and that edge alignment is a much stronger indicator of occlusion for poorly grouped than for strongly grouped inducers.