Knowledge that Transforms

Genetic mechanisms have been proposed to explain the pervasive representation of right-handedness in humans, whereas random, nongenetic factors have been posited to explain the lack of population-level right-handedness in nonhuman primates. We report evidence that hand preferences in chimpanzees are heritable, even among related individuals raised in different environments. Furthermore, we report that the degree of heritability is modified by factors associated with developmental instability, notably, offspring parity. The data are interpreted to reconcile both genetic models for handedness and hypotheses suggesting that developmental instability influences variation in handedness.

Most events are processed by a number of neural pathways. These pathways often differ considerably in processing speed. Thus, coherent perception requires some form of synchronization mechanism. Moreover, this mechanism must be flexible, because neural processing speed changes over the life of an organism. Here we provide behavioral evidence that humans can adapt to a new intersensory temporal relationship (which was artificially produced by delaying visual feedback). The conflict between these results and previous work that failed to find such improvements can be explained by considering the present results as a form of sensorimotor adaptation.

On the whole, people recognize objects best when they see the objects from a familiar view and worse when they see the objects from views that were previously occluded from sight. Unexpectedly, we found haptic object recognition to be viewpoint-specific as well, even though hand movements were unrestricted. This viewpoint dependence was due to the hands preferring the back "view" of the objects. Furthermore, when the sensory modalities (visual vs. haptic) differed between learning an object and recognizing it, recognition performance was best when the objects were rotated back-to-front between learning and recognition. Our data indicate that the visual system recognizes the front view of objects best, whereas the hand recognizes objects best from the back.

The present study reports four pairs of experiments that examined the role of nonpredictive (i.e., task-irrelevant) symbolic stimuli on attentional orienting. The experiments involved a simple detection task, an inhibition of return (IOR) task, and choice decision tasks both with and without attentional bias. Each pair of experiments included one experiment in which nonpredictive arrows were presented at the central fixation location and another experiment in which nonpredictive direction words (e.g., "up," "down," "left," "right") were presented. The nonpredictive symbolic stimuli affected responses in all experiments, with the words producing greater effects in the detection task and the arrows producing greater effects in the IOR and choice decision tasks. Overall, the present findings indicate that there is a strong connection between the overlearned representations of the meaning of communicative symbols and the reflexive orienting of visual attention.

The present article offers an approach to scientific debate called adversarial collaboration. The approach requires both parties to agree on empirical tests for resolving a dispute and to conduct these tests with the help of an arbiter. In dispute were Hertwig's claims that frequency formats eliminate conjunction effects and that the conjunction effects previously reported by Kahneman and Tversky occurred because some participants interpreted the word “and” in “bank tellers and feminists” as a union operator. Hertwig proposed two new conjunction phrases, “and are” and “who are,” that would eliminate the ambiguity. Kahneman disagreed with Hertwig's predictions for “and are,” but agreed with his predictions for “who are.” Mellers served as arbiter. Frequency formats by themselves did not eliminate conjunction effects with any of the phrases, but when filler items were removed, conjunction effects disappeared with Hertwig's phrases. Kahneman and Hertwig offer different interpretations of the findings. We discuss the benefits of adversarial collaboration over replies and rejoinders, and present a suggested protocol for adversarial collaboration.

This study investigated predictions of the life-span theory of selection, optimization, and compensation, focusing on different patterns of task priority during dual-task performance in younger and older adults. Cognitive (memorizing) and sensorimotor (walking a narrow track) performance were measured singly, concurrently, and when task difficulty was manipulated. Use of external aids was measured to provide another index of task priority. Before dual-task testing, participants received extensive training with each component task and external aid. Age differences in dual-task costs were greater in memory performance than walking, suggesting that older adults prioritized walking over memory. Further, when given a choice of compensatory external aids to use, older adults optimized walking, whereas younger adults optimized memory performance. The results have broad implications for systemic theories of cognitive and sensorimotor aging, and the costs and benefits of assistive devices and environmental support for older populations.

In recent years, several techniques have been developed to measure implicit social cognition. Despite their increased use, little attention has been devoted to their reliability and validity. This article undertakes a direct assessment of the interitem consistency, stability, and convergent validity of some implicit attitude measures. Attitudes toward blacks and whites were measured on four separate occasions, each 2 weeks apart, using three relatively implicit measures (response-window evaluative priming, the Implicit Association Test, and the response-window Implicit Association Test) and one explicit measure (Modern Racism Scale). After correcting for interitem inconsistency with latent variable analyses, we found that (a) stability indices improved and (b) implicit measures were substantially correlated with each other, forming a single latent factor. The psychometric properties of response-latency implicit measures have greater integrity than recently suggested.

This study used medium-term auditory repetition priming to investigate word-recognition processes. Highly fluent Catalan-Spanish bilinguals whose first language was either Catalan or Spanish were tested in a lexical decision task involving Catalan words and nonwords. Spanish-dominant individuals, but not Catalan-dominant individuals, exhibited repetition priming for minimal pairs differing in only one feature that is nondistinctive in Spanish (e.g.,[see text]), thereby indicating that they processed these words as homophones. This finding provides direct evidence both that word recognition uses a language-specific phonological representation and that lexical entries are stored in the mental lexicon as abstract forms.

Five studies studies that Chinese and Americans perceive change differently. Chinese anticipated more changes from an initial state than Americans did. When events were changing in a particular direction. Chinese were more likely than Americans to predict change in the direction of change. Moreover, for patterns with changing slopes, Chinese predicted greater change in the way slopes changed, in comparison to Americans. In addition, people who predicted change were perceived as wise by Chinese more than by Americans. Implications for social attribution, tolerance for contradiction, persistence on tasks, and the illusion of control are discussed.