Processing of information about location in brief visual displays

Within the context of the selective masking effect (Merikle, Coltheart, & Lowe, 1971), a series of five experiments investigated the utility of bar-marker probes as a poststimulus sampling procedure for partial report of brief visual displays. It was demonstrated that bar markers are inadequate as partial-report cues because subjects cannot properly locate the positions of the probes. An improved bar-marker procedure was developed which removed this problem of cue localization. Furthermore, it was shown that subjects, when given the opportunity, are able to report much more from brief visual displays than the bar-marker procedure typically permits. It was also suggested that subjects’ ability to employ bar-marker probes is governed by quite different factors than their capacity to report the contents of brief visual displays.     

Effects of spatial separation between stimuli in whole report from brief visual displays

Direct measurements of the effects of spatial separation between stimuli in whole report from brief visual displays are reported. The stimuli were presented on the periphery of an imaginary circle centered on fixation. In Experiment 1, each display showed two capital letters (letter height approximately equal 1.3 degrees, width approximately equal 0.9 degree, eccentricity approximately equal 5.5 degrees). The proportion of correctly reported letters was a strictly increasing, decelerating function of the spatial separation between the letters for center-to-center separations ranging from less than 2 degrees to more than 10 degrees of visual angle. Experiment 2 yielded similar results with triples of letters. Experiment 3 showed that accuracy increased with spatial separation for report of two short words, and Experiment 4 showed the same result for words presented upside down. The results are explained by a model of lateral masking (crowding) based on competitive interactions within receptive fields of cortical neurons.     

Context and learning in the processing of Information from brief visual displays

Research on visual detection with tachisto scopically presented multiple-element displays has indicated that a nonrandom sample of the elements is processed on any trial. The effect of learning on the sample composition was assessed with a task in which S reported whether matrices of nine letters contained one or two Xs. After a first session involving two-signal displays with signal pairs oriented either horizontally or vertically, two groups of nine Ss saw only one signal-pair orientation, while a comparison group continued to see all display types. The group that switched to all-vertical orientation significantly out-improved and outperformed the comparison group on the vertical two-signal displays, demonstrating that the central processing mechanism may adapt to take advantage of display pattern regularities.     

Attention and interference in the perception of brief visual displays

When a single target was displayed 100-200 ms after a five-item array, observers were remarkably poor at deciding whether or not the target was in the array; performance was much better when the target either preceded the array or followed it by a longer interval. This effect was independent of a number of visual display parameters, suggesting that it was not due to visual contour interaction. In addition, visual similarity did not interact with the effect, indicating that it probably did not occur during item identification either. However, when observers added one to a digit target before deciding whether it occurred in the array, the effect was substantially reduced. The results suggested a model in which abstract identity information about the target is confused with the array at certain temporal intervals. A quantitative version of this model fit the data quite well.     

Selective attention and target search with brief visual displays

In a series of four experiments, subjects were presented with eight item arrays tachistoscopically. In two tasks, the subject was required to recall a digit presented among seven letters or a letter among seven digits. The remaining tasks required the subject to detect the presence of a specific letter either in the context of seven random letters or seven digits. An examination of the effects of a masking stimulus for various target positions suggested that subjects could attend selectively when the target was a different category than its context but had to process the entire array when the target was the same category as the context. The effects of selective attention and masking are explained in terms of parallel and sequential identification processes.     

The extent of processing of noise elements during selective encoding from visual displays

Circular visual displays of 12 elements, consisting of A, H, M, and U, were presented to S. She responded with a lever movement in one direction if a given letter designated by a bar indicator was a member of the set A-U and in the opposite direction if it was from the other set. The principal experimental variables were the SOA by which the indicator preceded the display and whether the target letter was flanked by letters of the same or opposite set. The results indicated that the interference produced by noise letters is primarily on the response as opposed to the processing side. Also, there is a limit to the precision of selective attention in the visual field. The interference of opposite-set letters was inversely proportional to their distance from the target.     

Effects of number of items on the baboon's discrimination of same from different visual displays

Three experiments explored the baboon's discrimination of visual displays that comprised 2 to 24 black-and-white computer icons; the displayed icons were either the same as (same) or different from one another (different). The baboons' discrimination of same from different displays was a positive function of the number of icons. When the number of icons was decreased to 2 or 4, the baboons responded indiscriminately to the same and different displays, exhibiting strong position preferences. These results are both similar to and different from those of pigeons that were trained and tested under comparable conditions. Accepted after revision: 23 May 2001 Electronic Publication     

Length distortion of temporally extended visual displays: similarity to haptic spatial perception

Three experiments were designed to investigate length distortion--the tendency to inflate estimates of the inferred distance between two points, as the length of a circuitous pathway between them increases. This phenomenon, previously demonstrated with haptic and locomotor exploration (Lederman, Klatzky, Collins, & Wardell, 1987), was extended to vision through the presentation of pathways as a temporal sequence of illuminated points. The magnitude of the visual effect was less than that previously found in haptics, and conditions promoting the effect included a relatively slow presentation rate and moderately complex pathways. Commonalities in the pattern, if not the magnitude, of length distortion in vision and haptics suggest that similar processes of spatial encoding may underlie the phenomenon in both domains.     

Effects of stimulus probability and visual similarity on stimulus encoding

Visual similarity, stimulus probability, and stimulus contrast were manipulated in two memory-scanning experiments to determine how stimulus probability affects encoding. Two hypotheses were tested: The first, a featural facilitation hypothesis, localizes the effect of stimulus probability on feature extraction; the second claims that stimulus probability has its effect on stimulus recognition. In both experiments, visual similarity was found to slow encoding, particularly under low-contrast conditions. This effect was larger for low probability stimuli than for high probability stimuli and increased as the difference in probability between two visually similar stimuli increased. These results are inconsistent with the featural facilitation hypothesis, but can be explained in terms of differential priming of internal recognition responses for members of the stimulus set, such that more probable members are more easily recognized.     

Influence of similarity between target and irrelevant items on visual information processing.

6 undergraduate subjects searched circular stimulus displays of upper case letters of the alphabet for a pre-specified single target letter. The displays were given a masked exposure of 100 msec, and contained 1, 5, 11, or 17 irrelevant items which were either similar or dissimilar in shape to the target. It was anticipated that these conditions would provide a test of Neisser's (1967) notion of attention. The results, which showed that similarity, numbers and their interaction were significant, could not be explained by wholly serial or parallel models of information processing as they failed to account for the interaction. To explain the interaction it was necessary to consider processing by preattention and focal attention.     

Effects of increased processing load on parallel processing of visual displays

Display elements were sequentially painted upon a display scope in regular and irregular spatial-temporal orders. The primary result of Mayzner, Tresselt, and their associates is confirmed: within specified temporal-spatial limits, display elements may be perceptually blanked. Characteristics of perceptually blanked elements can, however, be revealed by forced-choice testing. The accuracy of tilt discrimination for perceptually blanked elements is equal to, or better than, that for nonblanked elements. Perceptually blanked elements can also be distinguished from absent and from partially absent elements, presumably on the basis of a crude brightness discrimination. Sequential blanking effects as revealed in the accuracy of slant detection, are not critically dependent upon the magnitude of uniform spacing between the display elements.     

On the time course of perceptual information that results from a brief visual presentation.

A briefly presented visual stimulus engenders an available-information function that lags behind the physical stimulus. We report two experiments that focus on the iconic-decay portion of this function, which falls to 0 over a 200-300 ms period following stimulus offset. In each experiment, to-be-reported digit strings were shown for varying durations followed by a noise mask at varying poststimulus intervals. We found the shape of the performance curve relating digit-report probability to stimulus exposure duration to be independent of stimulus-mask interstimulus interval. This finding is consistent with the proposition that the iconic-decay function's shape is independent of stimulus duration and allows us to identify this shape. We rejected exponential iconic decay for 6 of 8 observers; however, all observers' decay functions could be adequately fit by gamma decay, a generalization of exponential decay.     

Integration of information from multiple element displays

This experiment examined the processing of information from multiple element visual displays, using techniques derived from the theory of signal detectability. The method allows one to specify how observers integrate information from individual elements of a display. The experiment tested numerical and graphical displays having different display sizes, durations, and arrangements of elements. Observer performance increased with the number, m, of display elements, but at less than the ideal √m rate. Observer performance was consistent with a model of information integration constrained by internal noise. Linear arrays of elements resulted in better performance than did square arrays. Graphically coded elements resulted in better performance than did numerical elements. Observer decision weighting of element information from graphical displays was approximately uniform across spatial position, but the weighting of information from numerical displays was concentrated on elements near the fixation point.     

The effect of spatial frequency information and visual similarity in threat detection

In the current research, we sought to examine the role of spatial frequency on the detection of threat using a speeded visual search paradigm. Participants searched for threat-relevant (snakes or spiders) or non-threat-relevant (frogs or cockroaches) targets in an array of neutral (flowers or mushrooms) distracters, and we measured search performance with images filtered to contain different levels (high and low) of spatial frequency information. The results replicate previous work demonstrating more rapid detection of threatening versus non-threatening stimuli [e.g. LoBue, V. & DeLoache, J. S. (2008). Detecting the snake in the grass: Attention to fear-relevant stimuli by adults and young children. Psychological Science, 19, 284–289. doi:10.1111/j.1467-9280.2008.02081.x]. Most importantly, the results suggest that low spatial frequency or relatively coarse levels of visual information is sufficient for the rapid and accurate detection of threatening stimuli. Furthermore, the results also suggest that visual similarity between the stimuli used in the search tasks plays a significant role in speeded detection. The results are discussed in terms of the theoretical implications for the rapid detection of threat and methodological implications for properly accounting for similarity between the stimuli in visual search studies.