Evidence for preserved representations in change blindness

People often fail to detect large changes to scenes, provided that the changes occur during a visual disruption. This phenomenon, known as "change blindness," occurs both in the laboratory and in real-world situations in which changes occur unexpectedly. The pervasiveness of the inability to detect changes is consistent with the theoretical notion that we internally represent relatively little information from our visual world from one glance at a scene to the next. However, evidence for change blindness does not necessarily imply the absence of such a representation---people could also miss changes if they fail to compare an existing representation of the pre-change scene to the post-change scene. In three experiments, we show that people often do have a representation of some aspects of the pre-change scene even when they fail to report the change. And, in fact, they appear to "discover" this memory and can explicitly report details of a changed object in response to probing questions. The results of these real-world change detection studies are discussed in the context of broader claims about change blindness.     

Book Reviews : Galin Tihanov,The Master and the Slave: Lukács,Bakhtin, and the Ideas of their Time,Oxford University Press,New York, 2000, 327 pp.

Studies in East European Thought -     

Average size perception and the allure of a new mechanism

In this brief response to commentaries by Ariely (2008) and Chong, Joo, Emmanouil, and Treisman (2008) on our earlier article, we highlight the two key assumptions underlying earlier claims about statistical summary representations of object size and argue that existing studies have not met either of them. We note why statistical summary representations of size are different from such representations of motion or orientation, and we emphasize the need for simulations of performance to exclude focused attention explanations for judgments of average size.     

Better than average: alternatives to statistical summary representations for rapid judgments of average size

People can perceive the individual features of an object by focusing attention on it and binding the features together at a location. Some perceptual processing can occur without focusing attention on each object, though; people may even be able to extract summary information about the sizes of all the objects in a display, essentially computing the mean size at a glance. Evidence that people can judge the mean size of an array efficiently and accurately has been used to support the strong claim that people use a global, parallel process to extract a statistical summary of the average size of the objects in the display. Such claims are based both on the accuracy of performance and on the supposition that performance exceeds what would be possible with serial, focused attention. However, these studies typically have not examined the limits of performance with focused-attention strategies. Through experiments and simulations, we show that existing evidence for mean size perception can be explained through various focused-attention strategies, without appealing to a new mechanism of average size perception. Although our evidence does not eliminate the possibility that people do perceive the average size of all the objects in a display, it suggests that simpler mechanisms can accommodate the existing data.     

Action information from classification learning

University of Illinois at Urbana-Champaign, Urbana, Illinois Much of our learning comes from interacting with objects. Two experiments investigated whether or not arbitrary actions used during category learning with objects might be incorporated into object representations and influence later recognition judgments. In a virtual-reality chamber, participants used distinct arm movements to make different classification responses. During a recognition test phase, these same objects required arm movements that were consistent or inconsistent with the classification movement. In both experiments, consistent movements were facilitated relative to inconsistent movements, suggesting that arbitrary action information is incorporated into the representations.     

The importance of information localization in scene gist recognition

People can recognize the meaning or gist of a scene from a single glance, and a few recent studies have begun to examine the sorts of information that contribute to scene gist recognition. The authors of the present study used visual masking coupled with image manipulations (randomizing phase while maintaining the Fourier amplitude spectrum; random image structure evolution [RISE]; J. Sadr & P. Sinha, 2004) to explore whether and when unlocalized Fourier amplitude information contributes to gist perception. In 4 experiments, the authors found that differences between scene categories in the Fourier amplitude spectrum are insufficient for gist recognition or gist masking. Whereas the global 1/f spatial frequency amplitude spectra of scenes plays a role in gist masking, local phase information is necessary for gist recognition and for the strongest gist masking. Moreover, the ability to recognize the gist of a target image was influenced by mask recognizability, suggesting that conceptual masking occurs even at the earliest stages of scene processing.     

Naturalistic studies of aggressive behavior: aggressive stimuli, victim visibility, and horn honking.

Three studies extended laboratory research on aggression to a naturalistic setting which involved horn honking from drivers as a measure of aggression; the studies were adapted from Doob and Gross. The results from a survey (Study 1) of 59 drivers suggested that they were frequently irritated by and aggressive toward other drivers. A second study (using a 3x2 factorial design with 92 male drivers) indicated that manipulations of a rifle in an aggressive context and victim visibility (dehumanization) both significantly influenced horn honking rates subsequent to obstruction at a signal light. A third study with 137 male drivers and 63 female drivers examined the interactive effects of a rifle, an aggressively connotated bumper sticker, and individual subject characteristics (sex and an exploratory index of self-perceived status) on horn honking. The results for three studies in naturalistic settings offer possible extensions of laboratory based findings on aggression. The role of inhibitions in modifying the pattern of results was also discussed.     

Event-related potentials elicited by automatic targets: a dual-task analysis

The role of limited capacity processes in the detection of automatic targets was investigated in a dual-task paradigm using both behavioral and event-related brain potential (ERP) measures. An automatic detection task was paired with another concurrent discrimination while the relative importance of each task was systematically varied. The resulting performance operating characteristic (POC) showed that both the speed and accuracy of automatic detection responses were affected by the allocation of attention. Reductions in the accuracy of each task were accompanied by reductions in the amplitude of a late-positive component of the ERP (P300). In addition, the latency of the P300 component elicited by automatic targets was increased in dual-task conditions. A comparison of behavioral and ERP measures suggested the involvement of two separate limited-capacity processes in automatic detection: one concerned with the formation of an episodic representation of target occurrence and the other with the execution of rapid motor responses.     

The stimulating and inhibiting effects of weapons on Aggressive behavior

Evidence is presented suggesting that firearms violence is an important social problem. Research strongly suggests that the effectiveness of firearms as a cause of death and injury may be due to their widespread availability, their lethality, and the impulsivity of their use. The investigation of a possible causal link between firearms and impulsive aggression led to Berkowitz and LePage's (1967) weapons effect experiment. The results suggested that weapons can increase the instigation to aggression in aroused an uninhibited individuals. The researchers reasoned that weapons might stimulate aggression by classical conditioning processes resulting from learned associations between aggressive acts and weapons. Although a few studies have failed to reproduce an aggression-enhancing effect of weapons, the original finding has been replicated in several countries with diverse subject groups both in field and laboratory settings. However, these studies also indicate that many individuals may react with anxiety or fear in the presence of weapons and inhibit aggressive reactions. Manipulations of evaluation apprehension, subject suspiciousness, and/or hypothesis awareness about the purpose of the weapons in the experiments all seem to lead to reduced levels of aggressive response in the presence of weapons. These findings offer a possible explanation for the few failures to replicate the original weapons effect; if researchers used apprehensive subjects or subjects who were aware of possible experimental deceptions, they were more likely to observe an inhibitory reaction rather than an aggression-enhancing effect of weapons.