Knowledge that Transforms

When making explicit self-report ratings, members of status- and racial-minority groups report less personal experience with discrimination than that encountered by their group--a phenomenon called the personal/group discrimination discrepancy (PGDD). This study provides evidence, for the first time, that the PGDD may be, in part, a product of the procedure used to measure it. White women and men completed explicit and implicit measures of personal and group discrimination based on sex. The PGDD surfaced among women in the explicit measures, but not in the implicit measures. These findings suggest that explicit and implicit measures might provide different assessments of experience with discrimination.

We describe a methodology for investigating whether two manipulations exert independent effects on perception. This method avoids the strong scaling assumptions inherent to traditional analysis of variance techniques, and we used it to investigate the combined effects of cued visual attention and stimulus repetition. Subjects identified previously studied (primed) and new (unprimed) masked words that were presented to validly and invalidly cued locations for varying durations. Performance improved more rapidly with increasing exposure duration for primed than for unprimed, and for attended than for unattended, stimuli. We interpret this finding as indicating that both variables speed the rate of information acquisition. The speedup provided by priming and attention combined equaled the product of benefits for each alone, providing evidence they are serial, independent effects.

In choice between outcomes with different delays to reinforcement, most theories require that choice be governed by the ratio of the delays, not by the difference between them, a requirement also consistent with Weber's law. Instead, delay-reduction theory and optimal-foraging theory stipulate, under conditions of the present experiments, that the difference between the delays, and not the ratio between them, controls choice. This prediction was assessed using a procedure, widely used in foraging experiments, in which pigeons chose between accepting and rejecting either of two delays when offered. Across conditions, the delays either differed by a constant amount, with the ratio between the delays varying, or differed by changing amounts, with the ratio between the delays constant. In each of six experiments, rate of acceptance of the longer delay depended only on the difference between the two delays and not on the ratio between them, supporting delay-reduction and foraging theory.

People name well-known objects shown in pictures more quickly if they have studied them previously. The most common interpretation of this priming effect is that processing is facilitated by an implicit memory trace in a perceptual representation system. We show that object priming can be explained instead as a bias in information processing, without recourse to an implicit memory system. Assumptions about psychological decision-making processes and bias were added to a neural network model for object identification, and the model accounted for performance both qualitatively and quantitatively in four object identification experiments.

The inaugural issue of Psychological Science in the Public Interest (PSPI), a new publishing initiative by the American Psychological Society, accompanies this issue of Psychological Science. The report it contains, "Psychological Science Can Improve Diagnostic Decisions," by John Swets, Robyn Dawes, and John Monahan, represents a careful effort by those authors to summarize the potential of modern psychological science to enhance real-world diagnostic decisions. Such decisions (Is a cancer present? Will this individual commit violence? Will an impending storm strike? Will this applicant succeed?) are prevalent and crucial to the lives of individuals and to the well-being of our society. Subsequent issues of PSPI will address other important topics of public interest in areas where psychological science may have the potential to inform and improve public policy. Each of those reports will also represent the efforts of a distinguished team of scientists to report the available evidence, and the implications of that evidence, fairly and comprehensively. In this article, we describe the goals, procedures, and potential of PSPI.

We report evidence demonstrating that a search asymmetry favoring concave over convex targets can be reversed by altering the figure-ground assignment of edges in shapes. Visual search for a concave target among convex distractors is faster than search for a convex target among concave distractors (a search asymmetry). By using shapes with ambiguous local figure-ground relations, we demonstrated that search can be efficient (with search slopes around 10 ms/item) or inefficient (with search slopes around 30-40 ms/item) with the same stimuli, depending on whether edges are assigned to concave or convex "figures." This assignment process can operate in a top-down manner, according to the task set. The results suggest that attention is allocated to spatial regions following the computation of figure-ground relations in parallel across the elements present. This computation can also be modulated by top-down processes.

We tested the hypothesis that pigeons could use a cognitively efficient coding strategy by training them on a conditional discrimination (delayed symbolic matching) in which one alternative was correct following the presentation of one sample (one-to-one), whereas the other alternative was correct following the presentation of any one of four other samples (many-to-one). When retention intervals of different durations were inserted between the offset of the sample and the onset of the choice stimuli, divergent retention functions were found. With increasing retention interval, matching accuracy on trials involving any of the many-to-one samples was increasingly better than matching accuracy on trials involving the one-to-one sample. Furthermore, following this test, pigeons treated a novel sample as if it had been one of the many-to-one samples. The data suggest that rather than learning each of the five sample-comparison associations independently, the pigeons developed a cognitively efficient single-code/default coding strategy.

An animal that is rewarded for a response in one situation (the S+) is likely to respond to similar but recognizably different stimuli, the ubiquitous phenomenon of stimulus generalization. On the basis of functional analyses of the probabilistic structure of the world, Shepard formulated a universal law of generalization, claiming that generalization gradients, as a function of the appropriately scaled distance of a stimulus from S+, should be exponential in shape. This law was tested in spatial generalization in honeybees. Based on theoretically derived scales, generalization along both the dimensions of the distance from a landmark and the direction to a landmark followed Shepard's law. Support in an invertebrate animal increases the scope of the law, and suggests that the ecological structure of the world may have driven the evolution of cognitive structures in diverse animals.