Knowledge that Transforms

How efficiently do people integrate the disconnected image fragments that fall on their eyes when they view partly occluded objects? In the present study, I used a psychophysical summation-at-threshold technique to address this question by measuring discrimination performance with both isolated and combined features of physically fragmented but perceptually complete objects. If visual completion promotes superior integration efficiency, performance with a visually completed object should exceed what would be expected from performance with the individual object parts shown in isolation. Contrary to this prediction, results showed that discrimination performance with both static and moving versions of physically fragmented but perceptually complete objects was significantly worse than would be expected from performance with their constituent parts. These results present a challenge for future theories of visual completion.

Imagined intergroup contact (Crisp & Turner, 2009) is a new indirect contact strategy for promoting tolerance and more positive intergroup relations. McDonald, Donnellan, Lang, and Nikolajuk (2014) were unable to replicate the findings we obtained using a new variant of imagined contact (Birtel & Crisp, 2012). We commend the authors’ careful and systematic study, but we argue that their conclusion goes substantially beyond what their design, data, or context can justify. It overgeneralizes their finding to a field of more than 70 studies with multiple design variants and conceptual replications. Furthermore, the original study was designed not to test the efficacy of the basic imagined-contact effect, but rather to test the relative efficacy of different task variants. Therefore, we believe that it is more accurate to say that their study represents an important data point in efforts to identify moderators of imagined contact than to say that it provides data on the efficacy of the effect per se. We elaborate on these points and use this example to illustrate how direct replications and meta-analysis can be fruitfully combined to refine understanding of how imagined contact may most effectively reduce prejudice.

It remains an open question, however, whether this perception-action cycle is the result of direct visual stimulation only, or whether postural adjustments also occur when the motion of the visual stimulus is illusory. Here, we show that the latter is the case. Prolonged viewing of visual motion results in neural adaptation, and subsequent viewing of a stationary stimulus normally results in illusory motion in the opposite direction, a famous phenomenon known as the motion aftereffect (MAE; Anstis, Verstraten, & Mather, 1998). Surprisingly, this sequence of stimulation also causes postural sway in the direction consistent with the perceived illusory motion. Control test patterns that do not generate an MAE after identical adaptation do not induce sway. This suggests that the visuo-vestibular interactions that govern postural control are not influenced by visual stimulation per se, but can be modulated by an illusory motion signal (e.g., the internal neural signal responsible for the MAE).

The induction of categories and concepts from examples-which plays an important role in how people come to organize and understand the world-can happen at multiple levels, but how do competing values at these different levels affect learning? Using perceptually rich images of snakes, we asked participants to attend to either the snakes' specific genus or a broader categorization and then tested induction at both levels. We also varied the intrinsic value of the broader categorization (high value: whether the snake was venomous; low value: whether it was tropical). We found an interaction between study instruction and intrinsic value: Participants in the low-value condition were better able to induce the level they were instructed to attend to (i.e., genus or broader category) than to induce the level they were not instructed to attend to, whereas participants in the high-value condition, regardless of the level of categorization they were instructed to attend to, were significantly better at learning the broad categorization (for them, whether the snake was venomous) than were participants in the low-value condition. Our results suggest that intrinsically valuable features can disrupt the intentional learning of other, task-relevant information, but enhance the incidental learning of the same information.

Parents' antisocial behavior is associated with developmental risks for their offspring, but its effects on their children's cognitive ability are unknown. We used linked Swedish register data for a large sample of adolescent men (N = 1,177,173) and their parents to estimate associations between fathers' criminal-conviction status and sons' cognitive ability assessed at compulsory military conscription. Mechanisms behind the association were tested in children-of-siblings models across three types of sibling fathers with increasing genetic relatedness (half-siblings, full siblings, and monozygotic twins) and in quantitative genetic models. Sons whose fathers had a criminal conviction had lower cognitive ability than sons whose fathers had no conviction (any crime: Cohen's d = -0.28; violent crime: Cohen's d = -0.49). As models adjusted for more genetic factors, the association was gradually reduced and eventually eliminated. Nuclear-family environmental factors did not contribute to the association. Our results suggest that the association between men's antisocial behavior and their children's cognitive ability is not causal but is due mostly to underlying genetic factors.

Research on Nicaraguan Sign Language, created by deaf children, has suggested that young children use gestures to segment the semantic elements of events and linearize them in ways similar to those used in signed and spoken languages. However, it is unclear whether this is due to children's learning processes or to a more general effect of iterative learning. We investigated whether typically developing children, without iterative learning, segment and linearize information. Gestures produced in the absence of speech to express a motion event were examined in 4-year-olds, 12-year-olds, and adults (all native English speakers). We compared the proportions of gestural expressions that segmented semantic elements into linear sequences and that encoded them simultaneously. Compared with adolescents and adults, children reshaped the holistic stimuli by segmenting and recombining their semantic features into linearized sequences. A control task on recognition memory ruled out the possibility that this was due to different event perception or memory. Young children spontaneously bring fundamental properties of language into their communication system.

How do people sustain resources for the benefit of individuals and communities and avoid the tragedy of the commons, in which shared resources become exhausted? In the present study, we examined the role of serotonin activity and social norms in the management of depletable resources. Healthy adults, alongside social partners, completed a multiplayer resource-dilemma game in which they repeatedly harvested from a partially replenishable monetary resource. Dietary tryptophan depletion, leading to reduced serotonin activity, was associated with aggressive harvesting strategies and disrupted use of the social norms given by distributions of other players' harvests. Tryptophan-depleted participants more frequently exhausted the resource completely and also accumulated fewer rewards than participants who were not tryptophan depleted. Our findings show that rank-based social comparisons are crucial to the management of depletable resources, and that serotonin mediates responses to social norms.

It is generally thought that increased attention helps when one is learning a new task. However, using a dual-task paradigm, we showed that the rate of visuomotor learning was the same regardless of attentional distraction caused by a secondary task. Yet, when participants were tested later, a motor skill learned under distraction was remembered only when a similar distraction was present; when participants were tested without the distracting task, their performance reverted to untrained levels. This paradoxical result, in which the level of performance decreases when more attentional resources are available, suggests that the dual-task context, or the lack thereof, acts as a vital context for learning. This task-context-dependent "savings" was evident even when the specific secondary task or sensory modality differed between learning and recall; thus, the dual tasking, rather than the specific stimuli, provides context. This discovery suggests that the success of learning and rehabilitation programs may be diminished if they are developed without consideration of the role of task contexts.

Research on scene categorization generally concentrates on gist processing, particularly the speed and minimal features with which the "story" of a scene can be extracted. However, this focus has led to a paucity of research into how scenes are categorized at specific hierarchical levels (e.g., a scene could be a road or more specifically a highway); consequently, research has disregarded a potential diagnostically driven feedback process. We presented participants with scenes that were low-pass filtered so only their gist was revealed, while a gaze-contingent window provided the fovea with full-resolution details. By recording where in a scene participants fixated prior to making a basic- or subordinate-level judgment, we identified the scene information accrued when participants made either categorization. We observed a feedback process, dependent on categorization level, that systematically accrues sufficient and detailed diagnostic information from the same scene. Our results demonstrate that during scene processing, a diagnostically driven bidirectional interplay between top-down and bottom-up information facilitates relevant category processing.