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PubMed1996

Inattention magnifies perceived length: the attentional receptive field hypothesis.

Five experiments demonstrated that a briefly presented vertical line is judged as longer when it is unattended relative to when it is attended. This effect was obtained in estimating the length of 1 of 5 possible lines (Experiment 1) and in matching the length of a test line to a criterion line (Experiments 3 and 4). The directional effect of attention was eliminated when participants estimated the length difference between 2 simultaneously presented lines (Experiment 2). An additional matching experiment (Experiment 5) demonstrated similar lengthening effects for unattended lines and for unattended distances separated by vertically displaced dots. It is proposed that the metric for unattended stimuli is composed of large attentional receptive fields and that the final output is mediated by rounding up processes, so that the unattended line is systematically perceived as longer than the attended one.

Attention↗
PubMed1996

A constructive-associative model of the contextual dependence of unidimensional similarity.

Conditions under which pairwise dissimilarity ratings should reflect manipulations of the stimulus distribution were outlined by a model that proposed these effects. These conditions arise from either a context dependent process for constructing implicit scale values or a process that uses previously established stimulus-response associates. Consistent with the model, results from 3 experiments using unidimensional psychophysical stimuli demonstrated disordinal context effects on pairwise dissimilarity ratings when (a) there was a 3-s delay between presentation of pair members or (b) a unidimensional rating task preceded the pairwise dissimilarity ratings. Global effects of density were fit well by a model that extended A. Parducci's (1983) range-frequency theory to dissimilarity ratings. Local density effects were generally consistent with predictions from C.L.Krumhansl's (1978) distance-density theory.

Association Learning↗
PubMed1998

The contribution of covert attention to the set-size and eccentricity effects in visual search.

To reexamine the role of covert attention in visual search, the authors directly manipulated attention by peripherally cueing the target location and analyzed its effects on the set-size and the eccentricity effects. Observers participated in feature and conjunction tasks. Experiment 1 used precues, and Experiment 2 used postcues in a yes-no task under valid-, invalid-, and neutral-cueing conditions. Experiments 3 and 4 used a 2-interval alternative forced-choice visual-search task under cued and neutral conditions. Precueing the target location improved performance in feature and conjunction searches; postcueing did not. For the cued targets, the eccentricity effect for features and conjunctions was diminished, suggesting that the attentional mechanism improves the quality of the sensory representation of the attended location. The conjunction set-size effect was reduced but not eliminated. This questions serial-search models that attribute a major role to covert attention in visual search.

Adult↗
PubMed1999

Using eye height in different postures to scale the heights of objects.

Four experiments examined eye height (EH) scaling of object height across different postures. In Experiment 1, participants viewed rectangular targets while they were standing, seated, and prone. Standing and seated judgments were similar, possibly due to EH scaling. Prone judgments were significantly lower, a result not attributable to the unfamiliarity of that posture (Experiment 2). In Experiment 3, shifts of seated EH produced height overestimations equivalent to those of standing viewers. Experiment 4 examined the visual salience of size information in the seated and prone judgments by holding EH constant and manipulating another source: linear perspective. Participants viewed targets placed on true- and false-perspective (FP) gradients. The FP gradient affected prone judgments but not seated judgments, which presumably relied on EH. It appears that the human visual system weights size information differentially depending on its utility.

Adult↗
PubMed1999

Sequential priming in hierarchically organized figures: effects of target level and target resolution.

Three experiments are reported in which participants identified target letters that appeared at either the global or local level of hierarchically organized stimuli. It has been previously reported that response time is facilitated when targets on successive trials appear at the same level (L. M. Ward, 1982; L. C. Robertson, 1996). Experiments 1 and 2 showed that this sequential priming effect can be mediated by target-level information alone, independent of the resolution, or actual physical size, of targets. Target level and resolution were unconfounded by manipulating total stimulus size, such that global elements of the smaller stimuli subtended the same amount of visual angle as local elements of the larger stimuli. Experiment 3, however, showed that when level information is less useful than resolution in parsing targets from distractors, resolution does become critical in intertrial priming. These data are discussed as they relate to the role of attention in local vs. global (part vs. whole) processing.

Attention↗
PubMed2001

Monocular optical constraints on collision control.

A simulated ball-hitting task was used to explore the optical basis for collision control. Ball speed and size were manipulated in Experiments 1 and 2. Results showed a tendency for participants to respond earlier to slower and larger balls. Early in practice, participants would consistently miss the slowest and largest balls. Experiments 3 and 4 examined performance as a function of the range of speeds. Performance for identical speeds differed depending on whether the speeds were fastest or slowest within a range. Asymmetric transfer between the 2 ranges of speeds showed that those trained with slow speeds were very successful when tested with a faster range of speeds. Those trained with fast speeds did not do as well when tested on slower speeds. The pattern of results across 4 experiments suggests that participants were using optical angle and expansion rate as separate degrees of freedom for solving the collision task.

Analysis of Variance↗
PubMed1979

Interaction of stimulus size and retinal eccentricity in metacontrast masking.

Metacontrast masking occurs both at the fovea and in the retinal periphery; foveally, the smallest stimulus elicited the strongest masking, whereas peripherally the reverse was the case. An analysis of variance showed a significant size effect, eccentricity effect, and size-eccentricity interaction. As stimulus size increased, the stimulus onset asynchrony of maximum masking shifted to greater values. Both foveal metacontrast and peak shifts contradicted predictions made by the hypothesis that metacontrast is mediated by an interaction of sustained and transient channels in the visual system. The data are consistent, however, with a lateral inhibitory model of metacontrast masking and stimulus coding.

Discrimination Learning↗
PubMed1981

Mental measurement of line length: the role of the standard.

Reaction times were examined for magnitude estimates of line length. In the first two experiments, reaction times increased linearly with judged length. This result is consistent with the hypothesis the judgments are made by laying off a mental image of the standard along the line to be judged. The slope of the function relating judged length to reaction time was not affected by the length of the standard line, suggesting that the rate at which the image of the standard is laid off is not a function of the length of the standard. Reaction time also increased linearly with judged length when subjects judged line length when the standard of 1 in. was suggested but not provided as well as when no standard was suggested. The hypothesized laying-off process was compared to other cognitive manipulations, such as mental rotation and size scaling. Equivalence of judgments based on the representation of the standard in perceptual memory and in imagination is discussed.

Discrimination Learning↗
PubMed1983

Can response preparation begin before stimulus recognition finishes?

The present experiments were designed to determine whether information obtained early in the process of recognizing a stimulus can be used to begin preparing keypress responses before recognition of the stimulus has completely finished. This question is relevant to the recent debate between discrete (e.g., Sternberg, 1969a) and continuous (e.g., McClelland, 1979) models of human information processing. Stimulus sets were chosen so that recognition processes could extract incomplete preliminary information about a stimulus much faster than they could extract secondary information needed for unique stimulus identification. Discriminability of the secondary information was manipulated to vary the opportunity for response preparation based on preliminary information, with difficult secondary discriminations providing more time for response preparation than easy ones. Precues were given on some trials to allow response preparation to occur before the stimulus was presented, thereby reducing any difference in response preparation as a function of discriminability. Continuous models predict that precues should facilitate response preparation less when the secondary discrimination is difficult than when it is easy, and discrete models predict equal facilitation regardless of secondary discrimination difficulty. Evidence of response preparation was obtained with some but not all stimulus sets. The results were interpreted as support for the asynchronous discrete coding model (Miller, 1982a), in which response preparation can begin only after recognition processes have completely activated a code used in categorizing the stimulus.

Cues↗
PubMed1983

Spatial metrics of integral and separable dimensions.

Two experiments were conducted to investigate the relationship between dimensional integrality and the form of the combination rule or spatial metric used in a similarity judgment task. In Experiment 1, two groups of eight subjects judged the dissimilarity of all pairwise combinations of 12 rectangles differing in height and width (integral dimensions) or 12 circles differing in size and diameter orientation (separable dimensions). The dimensional organization and spatial metric of both sets of dimensions were determined. The results showed that differences in height and width contributed independently to judgments of the overall dissimilarity of rectangles and that these dimensions were combined using a Euclidean metric. In contrast, substantial interactions between circle size and diameter orientation were found. Combinations of these dimensions also appeared to violate the triangle inequality implying that no spatial metric was appropriate. In Experiment 2, parallelogram size and tilt were similarly analyzed. Although some degree of dimensional interaction was observed, it was found that on the average these dimensions were combined using a city-block metric. In a subsequent speeded classification task, orthogonal interference was observed, which suggested that size and tilt are integral dimensions. The implications of both experiments for the supposed association between the Euclidean metric and dimensional integrality are discussed.

Adolescent↗
PubMed1984

Selective attention and the organization of visual information.

Theories of visual attention deal with the limit on our ability to see (and later report) several things at once. These theories fall into three broad classes. Object-based theories propose a limit on the number of separate objects that can be perceived simultaneously. Discrimination-based theories propose a limit on the number of separate discriminations that can be made. Space-based theories propose a limit on the spatial area from which information can be taken up. To distinguish these views, the present experiments used small (less than 1 degree), brief, foveal displays, each consisting of two overlapping objects (a box with a line struck through it). It was found that two judgments that concern the same object can be made simultaneously without loss of accuracy, whereas two judgments that concern different objects cannot. Neither the similarity nor the difficulty of required discriminations, nor the spatial distribution of information, could account for the results. The experiments support a view in which parallel, preattentive processes serve to segment the field into separate objects, followed by a process of focal attention that deals with only one object at a time. This view is also able to account for results taken to support both discrimination-based and space-based theories.

Adolescent↗
PubMed1989

Varieties of size-specific visual selection.

Compared time to evaluate stimuli of varying sizes. When Ss expect an upcoming stimulus to be a certain size, response time increases with the disparity between expected and actual size. There are, however, 2 size adjustment processes, and they reflect 2 types of visual selection. In the first, a shape-specific image representation is used to separate a visual object from a superimposed distractor. These representations require the type of slow size scaling demonstrated in imagery experiments. The second size scaling process is faster and not shape-specific. At any given time the visual system is set to process information at a particular scale, and that scale can be adjusted to match an object's size. Because both selection mechanisms depend on size, they probably occur at a relatively low, spatially organized processing level. These findings lead to a new explanation for results that had been taken as evidence for attentional selection at the level of object representations.

Attention↗
PubMed1991

Predicting similarity and categorization from identification.

In this article, the relation between the identification, similarity judgment, and categorization of multidimensional perceptual stimuli is studied. The theoretical analysis focused on general recognition theory (GRT), which is a multidimensional generalization of signal detection theory. In one application, 2 Ss first identified a set of confusable stimuli and then made judgments of their pairwise similarity. The second application was to Nosofsky's (1985b, 1986) identification-categorization experiment. In both applications, a GRT model accounted for the identification data better than Luce's (1963) biased-choice model. The identification results were then used to predict performance in the similarity judgment and categorization conditions. The GRT identification model accurately predicted the similarity judgments under the assumption that Ss allocated attention to the 2 stimulus dimensions differently in the 2 tasks. The categorization data were predicted successfully without appealing to the notion of selective attention. Instead, a simpler GRT model that emphasized the different decision rules used in identification and categorization was adequate.

Adult↗
PubMed2000

Why do categories affect stimulus judgment?

The authors tested a model of category effects on stimulus judgment. The model holds that the goal of stimulus judgment is to achieve high accuracy. For this reason, people place inexactly represented stimuli in the context of prior information, captured in categories, combining inexact fine-grain stimulus values with prior (category) information. This process can be likened to a Bayesian statistical procedure designed to maximize the average accuracy of estimation. If people follow the proposed procedure to maximize accuracy, their estimates should be affected by the distribution of instances in a category. In the present experiments, participants reproduced one-dimensional stimuli. Different prior distributions were presented. The experiments verified that people's stimulus estimates are affected by variations in a prior distribution in such a manner as to increase the accuracy of their stimulus reproductions.

Adult↗
PubMed1991

Selective attention and search images in pigeons.

In a visual search task, pigeons detected targets when pretrial visual cues or blocked trial sequences signaled the target's identity. Sequential priming was robust over a wide range of intertrial intervals, but visual priming was unstable when the delay between cue offset and display onset was varied. Larger target set sizes enhanced sequential, but not visual, priming. Sequential priming did not depend on display size over the range of relatively large displays used. However, ambiguously cued targets in small displays were detected more quickly than primed targets in large displays. These findings suggest that naturalistic selection biases, or "search images," may be attributable to sequential priming and that the common attentional mechanism has moderately selective properties.

Animals↗
PubMed1995

Visual discrimination of pigmented skin lesions.

Three experiments explored human performance in discrimination of pigmented skin lesions from photographic slides. Experiment 1 showed that latent ability in identifying early melanoma was low, and some benign lesions tended to be falsely identified as serious. Performance overall did not decline when viewing time was reduced, suggesting that judgments could be made on the general appearance of lesions. Experiment 2 showed that enlargement of stimuli had no effect. Experiment 3 showed that performance was better with pictorial examples than with written descriptions for some classes of lesion, but for melanoma performance improved with longer viewing time when information was provided, suggesting that an opportunity to scrutinize could be beneficial. Guidelines to the public should distinguish melanoma from benign lesions and stress the importance of seeking prompt medical attention for suspicious lesions.

Adolescent↗