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.

Grainger, Dufau, Montant, Ziegler, and Fagot (2012a) taught 6 baboons to discriminate words from nonwords in an analogue of the lexical decision task. The baboons more readily identified novel words than novel nonwords as words, and they had difficulty rejecting nonwords that were orthographically similar to learned words. In a subsequent test (Ziegler, Hannagan, et al., 2013), responses from the same animals evinced a transposed-letter effect. These three effects, when seen in skilled human readers, are taken as hallmarks of orthographic processing. We show, by simulation of the unique learning trajectory of each baboon, that the results can be interpreted equally well as an example of simple, familiarity-based discrimination of pixel maps without orthographic processing.

The visual world is flooded with ambiguity. Generally, people can resolve the ambiguity almost instantaneously, as when they distinguish at a glance whether a maiden in a portrait by Picasso is in profile or facing front. However, perception of the same reality, though relatively stable at the individual level, can vary dramatically from person to person, manifesting idiosyncratic perceptual biases. What drives the heterogeneity of human vision as reflected in the resolution of visual ambiguity? Using the twin method, we demonstrated a significant genetic contribution to individual differences in the visual disambiguation of bistable biological-motion stimuli but not inanimate motion stimuli. These findings challenge the prevailing view that the way the human brain makes sense of visual input is largely shaped by a person's perceptual history. Rather, the visual perception of biologically salient information can be guided by adaptive mental "priors" that are genetically transmitted.

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.

Perceptual processes generally enhance borders, because of their high information value. Mach bands are an example in vision. In the social world, borders are also of special significance; one side of a border is generally more esteemed or valued than the other. We claim that entities (individuals, groups) that are just over the border on the positive side tend to exaggerate their membership on the positive side (asymmetrical social Mach bands). We demonstrate this by showing that (a) master's-degree universities use the word university to describe themselves more than major graduate universities do, (b) small international airports use the word international to describe themselves more than major airports do, and (c) University of Pennsylvania students, who are affiliated with a "marginal" Ivy League school, use the word Ivy to describe their school more than Harvard students do.