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Perception & Psychophysics

Yuhong V Jiang, Won Mok Shim, Tal Makovski
Previous studies have shown that the number of objects we can actively hold in visual working memory is smaller for more complex objects. However, complex objects are not just more complex but are often more similar to other complex objects used as test probes. To separate effects of complexity from effects of similarity, we measured visual memory following a 1-sec delay for complex and simple objects at several levels of memory-to-test similarity. When memory load was one object, memory accuracy for a face (a complex attribute) was similar to a line orientation (a simple attribute) when the face changed in steps of 10% along a morphing continuum and the line changed in steps of 5 degrees in orientation...
November 2008: Perception & Psychophysics
Dennis M Shaffer, Andrew B Maynor, Windy L Roy
The present work demonstrates that observers grossly underestimate the length of lines parallel to their line of sight. In Experiment 1, observers, working from memory, estimated the length of a dashed line on the road to be 0.61 m. This result is consistent with observers' using an average visual angle converted to the physical length of visible lines on the road to estimate their length. In Experiment 2, observers gave verbal and matching estimates that significantly underestimated the length of a 3.05-m line on the ground that was parallel to their line of sight...
November 2008: Perception & Psychophysics
Lisa D Sanders, Amy S Joh, Rachel E Keen, Richard L Freyman
The ability to isolate a single sound source among concurrent sources and reverberant energy is necessary for understanding the auditory world. The precedence effect describes a related experimental finding, that when presented with identical sounds from two locations with a short onset asynchrony (on the order of milliseconds), listeners report a single source with a location dominated by the lead sound. Single-cell recordings in multiple animal models have indicated that there are low-level mechanisms that may contribute to the precedence effect, yet psychophysical studies in humans have provided evidence that top-down cognitive processes have a great deal of influence on the perception of simulated echoes...
November 2008: Perception & Psychophysics
Stephen M Emrich, Justin D N Ruppel, Naseem Al-Aidroos, Jay Pratt, Susanne Ferber
If some of the distractors in a visual search task are previewed prior to the presentation of the remaining distractors and the target, search time is reduced relative to when all of the items are displayed simultaneously. Here, we tested whether the ability to preferentially search new items during such a preview search is limited. We confirmed previous studies: The proportion of fixations on old items was significantly less than chance. However, the probability of fixating old locations was negatively affected by increasing the number of previewed distractors, suggesting that inhibition is limited to a small number of old items...
November 2008: Perception & Psychophysics
Hyosun Kim, Yang Seok Cho, Motonori Yamaguchi, Robert W Proctor
Three experiments tested whether the Stroop color-naming effect is a consequence of word recognition's being automatic or of the color word's capturing visual attention. In Experiment 1, a color bar was presented at fixation as the color carrier, with color and neutral words presented in locations above or below the color bar; Experiment 2 was similar, except that the color carrier could occur in one of the peripheral locations and the color word at fixation. The Stroop effect increased as display duration increased, and the Stroop dilution effect (a reduced Stroop effect when a neutral word is also present) was an approximately constant proportion of the Stroop effect at all display durations, regardless of whether the color bar or color word was at fixation...
November 2008: Perception & Psychophysics
Derrick G Watson, Jason J Braithwaite, Glyn W Humphreys
Visual search can benefit when one set of distractors is presented as a preview, prior to the appearance of the second set of distractors plus the target (Watson & Humphreys, 1997). It has been shown that changing the shape of the old, previewed stimuli when the new items appear causes the old stimuli to recompete for selection with the new ones. In contrast, changing the luminance or color of the old stimuli has no detrimental effects. Here, we present five experiments that reassessed the effect of luminance changes in preview search...
November 2008: Perception & Psychophysics
Juan M Toro, Mohinish Shukla, Marina Nespor, Ansgar D Endress
Consonants and vowels may play different roles during language processing, consonants being preferentially involved in lexical processing, and vowels tending to mark syntactic constituency through prosodic cues. In support of this view, artificial language learning studies have demonstrated that consonants (C) support statistical computations, whereas vowels (V) allow certain structural generalizations. Nevertheless, these asymmetries could be mere by-products of lower level acoustic differences between Cs and Vs, in particular the energy they carry, and thus their relative salience...
November 2008: Perception & Psychophysics
Karin M Bausenhart, Bettina Rolke, Rolf Ulrich
Recent research shows that temporal preparation within a constant foreperiod design improves the spatial resolution of visual perception. The present experiments were designed to investigate whether similar benefits of temporal preparation can be observed in a task that requires high temporal resolution. In three experiments, we assessed the effect of temporal preparation on temporal order judgments (TOJs). In Experiment 1, short foreperiods facilitated TOJ for two spatially adjacent dots. This finding was replicated in Experiment 2, in which the temporal order of two spatially overlapping stimuli ("+" and "x") had to be discriminated...
November 2008: Perception & Psychophysics
Feng Du, Richard A Abrams
In the spatial blink paradigm, participants search for a target of a designated color in a rapidly presented stream of letters at fixation. Target identification is typically impaired if a peripheral distractor appears shortly before the target, inducing a spatial blink, but impairment is observed only when the distractor also shares the sought-for color. Such results reveal an important top-down influence on the capture of attention. In the present experiments, we examined the influence of the bottom-up transients associated with the appearance and disappearance of distractors in the spatial blink paradigm...
November 2008: Perception & Psychophysics
Gordon E Legge, Cindee Madison, Brenna N Vaughn, Allen M Y Cheong, Joseph C Miller
Previous studies of tactile acuity on the fingertip, using passive touch, have demonstrated an age-related decline in spatial resolution for both sighted and blind subjects. We have reexamined this age dependence with two newly designed tactile-acuity charts that require active exploration of the test symbols. One chart used dot patterns similar to braille, and the other used embossed Landolt rings. Groups of blind braille readers and sighted subjects ranging from 12 to 85 years old were tested in two experiments...
November 2008: Perception & Psychophysics
John W Philbeck, Adam J Woods, Joeanna Arthur, Jennifer Todd
Blind walking has become a common measure of perceived target location. This article addresses the possibility that blind walking might vary systematically within an experimental session as participants accrue exposure to nonvisual locomotion. Such variations could complicate the interpretation of blind walking as a measure of perceived location. We measured walked distance, velocity, and pace length in indoor and outdoor environments (1.5-16.0 m target distances). Walked distance increased over 37 trials by approximately 9...
November 2008: Perception & Psychophysics
Eva Belke, Glyn W Humphreys, Derrick G Watson, Antje S Meyer, Anna L Telling
Moores, Laiti, and Chelazzi (2003) found semantic interference from associate competitors during visual object search, demonstrating the existence of top-down semantic influences on the deployment of attention to objects. We examined whether effects of semantically related competitors (same-category members or associates) interacted with the effects of perceptual or cognitive load. We failed to find any interaction between competitor effects and perceptual load. However, the competitor effects increased significantly when participants were asked to retain one or five digits in memory throughout the search task...
November 2008: Perception & Psychophysics
Zhe Chen, Kyle R Cave
Previous studies have concluded that object-based attention does not always arise if attention is cued endogenously (Macquistan, 1997) or if the target location is known with certainty (Shomstein & Yantis, 2002). In the Experiments reported here, we found object-based attention even when the locations of the two targets were known with certainty due to presentation of an endogenous cue. However, object-based attention can be prevented by limiting the exposure time of the object stimuli. These findings provide additional evidence against a search prioritization account of object-based attention...
November 2008: Perception & Psychophysics
Gernot Horstmann, Stefanie I Becker
Recent research has substantiated that schematic negative faces are found more efficiently than positive faces among crowds of distractor faces of varying set sizes. The present study asks whether this relative search asymmetry (RSA) is intention driven or due to involuntary attentional capture. To that aim, participants were first tested in a condition in which negative and positive faces were searched for, and then in a condition in which negative or positive schematic faces appeared at chance level at the position of the target (valid trials) or of a distractor (invalid trials), the faces thus being task irrelevant (the 1/n paradigm)...
November 2008: Perception & Psychophysics
Christine Lefebvre, Denis Cousineau, Serge Larochelle
Schneider and Shiffrin (1977) proposed that training under consistent stimulus-response mapping (CM) leads to automatic target detection in search tasks. Other theories, such as Treisman and Gelade's (1980) feature integration theory, consider target-distractor discriminability as the main determinant of search performance. The first two experiments pit these two principles against each other. The results show that CM training is neither necessary nor sufficient to achieve optimal search performance. Two other experiments examine whether CM trained targets, presented as distractors in unattended display locations, attract attention away from current targets...
November 2008: Perception & Psychophysics
Marisa Carrasco, Stuart Fuller, Sam Ling
Carrasco, Ling, and Read (2004) showed that transient attention increases perceived contrast. However, Prinzmetal, Long, and Leonhardt (2008) suggest that for targets of low visibility, observers may bias their response toward the cued location, and they propose a cue-bias explanation for our previous results. Our response is threefold. First, we outline several key methodological differences between the studies that could account for the different results. We conclude that the cue-bias hypothesis is a plausible explanation for Prinzmetal et al...
October 2008: Perception & Psychophysics
Yousri Marzouki, Martijn Meeter, Jonathan Grainger
In two masked repetition priming experiments with letter stimuli, the positions of prime and target stimuli were varied horizontally from fixation. Priming effects did not interact with position when prime and target location covaried (Experiment 1A) but diminished with increasing prime eccentricity when targets were always centrally located (Experiment 1B). Two accounts of this pattern of priming effects were proposed that postulate two different mechanisms over and above effects of visual acuity. The integration account postulates degree of separation of prime and target stimuli as the critical factor, and the attentional account postulates spatial attention as the critical factor...
October 2008: Perception & Psychophysics
Petra M J Pollux, Patrick A Bourke
Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations nearer the viewer once attention is deployed to a spatially cued object in depth. Previously, this effect (initially referred to as the near effect) was attributed to access of a 3-D viewer-centered spatial representation for guiding attention in 3-D space. The aim of this study was to investigate whether the near effect could have been associated with the position of the response hand, which was always near the viewer in previous studies that investigated endogenous attentional shifts in real depth...
October 2008: Perception & Psychophysics
Huanping Dai
In certain perceptual discrimination tasks, a change in a particular stimulus variable can be perceived as changes along multiple perceptual dimensions. If the study is primarily concerned with a particular perceptual dimension or cue, it is important that the experimenter keep the influences of the other unwanted but correlated perceptual cues under control. One way to accomplish this objective is to randomize the stimuli along the stimulus dimensions primarily associated with these unwanted cues, making them unreliable as a basis for the discrimination...
October 2008: Perception & Psychophysics
Krista A Ehinger, James R Brockmole
Because the importance of color in visual tasks such as object identification and scene memory has been debated, we sought to determine whether color is used to guide visual search in contextual cuing with real-world scenes. In Experiment 1, participants searched for targets in repeated scenes that were shown in one of three conditions: natural colors, unnatural colors that remained consistent across repetitions, and unnatural colors that changed on every repetition. We found that the pattern of learning was the same in all three conditions...
October 2008: Perception & Psychophysics
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