Knowledge that Transforms

Prior research has found inconsistent effects of diversity on group performance. The present research identifies hormonal factors as a critical moderator of the diversity-performance connection. Integrating the diversity, status, and hormone literatures, we predicted that groups collectively low in testosterone, which orients individuals less toward status competitions and more toward cooperation, would excel with greater group diversity. In contrast, groups collectively high in testosterone, which is associated with a heightened status drive, would be derailed by diversity. Analysis of 74 randomly assigned groups engaged in a group decision-making exercise provided support for these hypotheses. The findings suggest that diversity is beneficial for performance, but only if group-level testosterone is low; diversity has a negative effect on performance if group-level testosterone is high. Too much collective testosterone maximizes the pains and minimizes the gains from diversity.

We report a novel visual phenomenon called the rejuvenation effect. It causes an "old" object that has been on view for some time to acquire the properties of a suddenly appearing new object. In each experiment, a square outline was displayed continuously on one side of fixation. The target (an asterisk) was presented either inside the square or on the opposite side of fixation. On half of the trials, a transient visual or auditory event preceded the target. In Experiment 1a ( N = 139), response times were faster when the target appeared inside the square, but only when it was preceded by a transient event, consistent with the network-reset theory of locus coeruleus-norepinephrine (LC-NE) phasic activation. Three further experiments confirmed the predictions of network-reset theory, including the absence of rejuvenation in participants with atypical LC-NE functioning (individuals with symptoms of autism spectrum disorder). These findings provide new perspectives on what causes a visual object to be perceived as new.

Hypodescent is the phenomenon of categorizing biracial individuals asymmetrically (e.g., viewing Black-White biracial individuals as Black instead of White). We propose that hypodescent is explained by domain-general attentional biases toward dangerous and distinctive components in conceptual representation. This cognitive mechanism derives its empirical support from several research traditions, especially from research on how people evaluate generic statements. Here, we demonstrate how liquid mixtures are categorized in ways characteristic of hypodescent. Mixtures that contain equal amounts of two liquids are categorized as whichever liquid is more dangerous or distinctive (Study 1). Dangerous and distinctive components are prioritized even when they are less than 50% of the mixture (Study 2). The relative dangerousness or distinctiveness of liquids (Study 3) or racial groups (Study 4) predicts the strength and direction of this asymmetry. We discuss how conceptual prominence relates to previous theories of hypodescent.

Visual space is perceived as continuous and stable even though visual inputs from the left and right visual fields are initially processed separately within the two cortical hemispheres. In the research reported here, we examined whether the visual system utilizes a dynamic recalibration mechanism to integrate these representations and to maintain alignment across the visual fields. Subjects adapted to randomly oriented moving lines that straddled the vertical meridian; these lines were vertically offset between the left and right hemifields. Subsequent vernier alignment judgments revealed a negative aftereffect: An offset in the same direction as the adaptation was required to correct the perceived misalignment. This aftereffect was specific to adaptation to vertical, but not horizontal, misalignments and also occurred following adaptation to movie clips and patterns without coherent motion. Our results demonstrate that the visual system unifies the left and right halves of visual space by continuously recalibrating the alignment of elements across the visual fields.

Even experts routinely miss infrequent targets, such as weapons in baggage scans or tumors in mammograms, because the visual system is not equipped to notice the unusual. To date, limited progress has been made toward improving human factors that mediate such critical diagnostic tasks. Here, we present a novel framework for pairing individuals' estimates to increase target detection. Using a wisdom-of-crowds approach that capitalizes on the visual system's ability to efficiently combine information, we demonstrated how averaging two noninteracting individuals' continuous estimates of whether a briefly presented image contained a prespecified target can significantly boost detection across a range of tasks. Furthermore, we showed how pairing individuals' estimates to maximize decorrelated patterns of performance in one task can optimize performance on a separate task. These results make significant advances toward combating severe deficits in target detection using straightforward applications for maximizing performance within limited pools of observers.

Although mental simulation underlies many day-to-day judgments, we identified a new domain influenced by simulation: volume estimation. Previous research has identified various ways in which volume estimates are biased but typically has not presented a psychological process by which such judgments are made. Our simulation-informs-perception account proposes that people often estimate a container's size by simulating filling it. First, this produces an orientation effect: The same container is judged larger when right side up than when upside down because of the greater ease of imagining filling an upright container. Second, we identified a cavern effect: Imagining pouring water through a narrow opening toward a relatively wide base produces a sense that the container is cavernous and large (compared with identically sized, wide-topped, narrow-based containers). By testing for and demonstrating the importance of simulation to these effects, we showed how complex perceptual judgments can be distorted by higher level cognitive influences even when they are necessarily informed by modularly processed perceptual input.

Relative numerosity is traditionally studied using texture pairs. Observers must decide which member of each pair has the greater total number of texture elements. In the present experiment, textures were segregated into nonoverlapping "sectors" containing between zero and four elements, and our observers were asked to select the texture containing the greater average number of texture elements (per sector). If observers were more sensitive to total numerosity than average numerosity, their performance (quantified by the just-noticeable Weber fraction) should have been better when the two textures occupied the same number of sectors than when they occupied unequal numbers of sectors. However, we recorded Weber fractions between 11% and 13% for all observers in all conditions. This performance was comparable with an otherwise-ideal observer whose decisions were based on between three and five sectors in each texture. We conjecture that traditional numerosity discriminations are based on similarly small numbers of element clusters.

Imagine hearing someone call a particular dalmatian a "dax." The meaning of the novel noun dax is ambiguous between the subordinate meaning (dalmatian) and the basic-level meaning (dog). Yet both children and adults successfully learn noun meanings at the intended level of abstraction from similar evidence. Xu and Tenenbaum (2007a) provided an explanation for this apparent puzzle: Learners assume that examples are sampled from the true underlying category (strong sampling), making cases in which there are more observed exemplars more consistent with a subordinate meaning than cases in which there are fewer exemplars (the suspicious-coincidence effect). Authors of more recent work (Spencer, Perone, Smith, & Samuelson, 2011) have questioned the relevance of this finding, however, arguing that the effect occurs only when the examples are presented to the learner simultaneously. Across a series of 12 experiments ( N = 600), we systematically manipulated several experimental parameters that varied across previous studies, and we successfully replicated the findings of both sets of authors. Taken together, our data suggest that the suspicious-coincidence effect in fact is robust to presentation timing of examples but is sensitive to another factor that varied in the Spencer et al. (2011) experiments, namely, trial order. Our work highlights the influence of pragmatics on behavior in experimental tasks.