Knowledge that Transforms

Galton (1907) first demonstrated the "wisdom of crowds" phenomenon by averaging independent estimates of unknown quantities given by many individuals. Herzog and Hertwig (2009; hereafter H&H in Psychological Science) showed that individuals' own estimates can be improved by asking them to make two estimates at separate times and averaging them. H&H claimed to observe far greater improvement in accuracy when participants received "dialectical" instructions to consider why their first estimate might be wrong before making their second estimates than when they received standard instructions. We reanalyzed H&H's data using measures of accuracy that are unrelated to the frequency of identical first and second responses and found that participants in both conditions improved their accuracy to an equal degree.

The visual system is intelligent--it is capable of recovering a coherent surface from an incomplete one, a feat known as perceptual completion or filling in. Traditionally, it has been assumed that surface features are interpolated in a way that resembles the fragmented parts. Using displays featuring four circular apertures, we showed in the study reported here that a distinct completed feature (horizontal motion) arises from local ones (oblique motions)-we term this process emergent filling in. Adaptation to emergent filling-in motion generated a dynamic motion aftereffect that was not due to spreading of local motion from the isolated apertures. The filling-in motion aftereffect occurred in both modal and amodal completions, and it was modulated by selective attention. These findings highlight the importance of high-level interpolation processes in filling in and are consistent with the idea that during emergent filling in, the more cognitive-symbolic processes in later areas (e.g., the middle temporal visual area and the lateral occipital complex) provide important feedback signals to guide more isomorphic processes in earlier areas (V1 and V2).

We investigated 1-year-old infants' ability to infer an adult's focus of attention solely on the basis of her voice direction. In Studies 1 and 2, 12- and 16-month-olds watched an adult go behind a barrier and then heard her verbally express excitement about a toy hidden in one of two boxes at either end of the barrier. Even though they could not see the adult, infants of both ages followed her voice direction to the box containing the toy. Study 2 showed that infants could do this even when the adult was positioned closer to the incorrect box while she vocalized toward the correct one (and thus ruled out the possibility that infants were merely approaching the source of the sound). In Study 3, using the same methods as in Study 2, we found that chimpanzees performed the task at chance level. Our results show that infants can determine the focus of another person's attention through auditory information alone-a useful skill for establishing joint attention.

Processes of proactive interference were explored using the pigeon as a model system of memory. This study shows that proactive interference extends back in time at least 16 trials (and as many minutes), revealing a continuum of interference and providing a framework for studying memory. Pigeons were tested in a delayed same/different task containing trial-unique pictures. On interference trials, sample pictures from previous trials reappeared as test pictures on different trials. Proactive-interference functions showed greatest interference from the most recent trial and with the longer of two delays (10 s vs. 1 s). These interference functions are accounted for by a time-estimation model based on signal detection theory. The model predicts that accuracy at test is determined solely by the ratio of the elapsed time since the offset of the current-trial sample to the elapsed time since the offset of the interfering sample. Implications for comparing memory of different species and different types of memory (e.g., familiarity vs. recollection) are discussed.

In two scenario-based studies, we found that women and men evaluate glass-cliff positions (i.e., precarious leadership positions at organizations in crisis) differently depending on the social and financial resources available. Female and male participants evaluated a hypothetical leadership position in which they would have both social and financial resources, financial resources but no social resources, or social resources but no financial resources. Women evaluated the position without social resources most negatively, whereas men evaluated the position without financial resources most negatively. In study 2, we found that women and men considered different issues when evaluating these leadership positions. Women's evaluations and expected levels of influence as leaders depended on the degree to which they expected to be accepted by subordinates. In contrast, men's evaluations and expected levels of acceptance by subordinates depended on the degree to which they expected to be influential in the position. Our findings have implications for the understanding of the glass-cliff phenomenon and gendered leadership stereotypes.

Taking a memory test after an initial study phase produces better long-term retention than restudying the items, a phenomenon known as the testing effect. We propose that this effect emerges because testing strengthens semantic features of items' memory traces, whereas restudying strengthens surface features of items' memory traces. This novel account predicts that a testing effect should be observed even after a short retention interval when a language switch occurs between the learning phase and the final test phase. We assessed this prediction with Dutch-English bilinguals who learned Dutch Deese-Roediger-McDermott word lists through restudying or through testing (retrieval practice). Five minutes after this learning phase, they took a recognition test in Dutch (within-language condition) or in English (across-language condition). We observed a testing effect in the across-language condition, but not in the within-language condition. These findings corroborate our novel account of the testing effect.

Five studies examined whether the practice of regifting--a social taboo--is as offensive to the original givers as potential regifters assume. Participants who imagined regifting a gift (receivers) thought that the original giver would be more offended than participants who imagined that their gifts were regifted (givers) reported feeling. Specifically, receivers viewed regifting as similar in offensiveness to throwing gifts away, yet givers clearly preferred the former. This asymmetry in emotional reactions to regifting was driven by an asymmetry in beliefs about entitlement. Givers believed that the act of gift giving passed title to the gift on to receivers, so that receivers were free to decide what to do with the gift; in contrast, receivers believed that givers retained some say in how their gifts were used. Finally, an intervention designed to destigmatize regifting by introducing a different normative standard (i.e., National Regifting Day) corrected the asymmetry in beliefs about entitlement and increased regifting.

Human aging is associated with decline in cognitive and physical functioning. Although pulmonary function predicts long-term performance (up to 10 years) on measures of cognitive function, recent data suggest the opposite relationship: Cognitive decline predicts self-reported physical limitations. In the study reported here, we utilized dual-change-score models to determine the directional relationship between pulmonary and cognitive function. Our sample consisted of 832 participants (ages 50-85 years at baseline), who were assessed in up to seven waves of testing across 19 years as part of the longitudinal Swedish Adoption/Twin Study of Aging. Changes in pulmonary function led to subsequent changes in fluid cognitive function, specifically, in tasks reflecting psychomotor speed and spatial abilities. There was no evidence that declines in cognitive function led to subsequent declines in pulmonary function. Thus, these data indicate a directional relationship from decreased pulmonary function to decreased cognitive function, a finding that underscores the importance of maintaining pulmonary function to ensure cognitive performance.

In October of 2011, the U.S. Preventive Services Task Force released a draft report in which they recommended against using the prostate-specific antigen (PSA) test to screen for prostate cancer. We attempt to show that four factors documented by psychological research can help explain the furor that followed the release of the task force's report. These factors are the persuasive power of anecdotal (as opposed to statistical) evidence, the influence of personal experience, the improper evaluation of data, and the influence of low base rates on the efficacy of screening tests. We suggest that augmenting statistics with facts boxes or pictographs might help such committees communicate more effectively with the public and with the U.S. Congress.