Hemispheric processing of global form, local form, and texture.

Hemispheric processing of global form, local form, and texture of hierarchical patterns composed of many, relatively small elements and patterns composed of few, relatively large elements was examined in two experiments, employing a Stroop-type paradigm. In experiment 1 subjects were instructed to attend either to the global or the local level of the pattern and to identify the form at the designated level. In experiment 2 subjects were to identify the global form or the texture. A right visual field (left hemisphere) advantage was obtained for detection of local form, and a left visual field (right hemisphere) advantage was obtained for detection of global form. When many-element patterns were processed in terms of global form and texture, the results failed to show reliable hemispheric differences. The results suggest that the hemispheres differ in their sensitivity to the relatively more global versus the relatively more local aspects of visual patterns which require focused attention (as in global/local form detection). When the task involved distributed attention (as in texture detection) no lateralized effects were observed.     

Multielement visual tracking: attention and perceptual organization.

Two types of theories have been advanced to account for how attention is allocated in performing goal-directed visual tasks. According to location-based theories, visual attention is allocated to spatial locations in the image; according to object-based theories, attention is allocated to perceptual objects. Evidence for the latter view comes from experiments demonstrating the importance of perceptual grouping in selective-attention tasks. This article provides further evidence concerning the importance of perceptual organization in attending to objects. In seven experiments, observers tracked multiple randomly moving visual elements under a variety of conditions. Ten elements moved continuously about the display for several seconds; one to five of them were designated as targets before movement initiation. At the end of movement, one element was highlighted, and subjects indicated whether or not it was a target. The ease with which the elements in the target set could be perceptually grouped was systematically manipulated. In Experiments 1-3, factors that influenced the initial formation of a perceptual group were manipulated; this affected performance, but only early in practice. In Experiments 4-7, factors that influenced the maintenance of a perceptual group during motion were manipulated; this affected performance throughout practice. The results suggest that observers spontaneously grouped the target elements and directed attention toward this coherent but nonrigid virtual object. This supports object-based theories of attention and demonstrates that perceptual grouping, which is usually conceived of as a purely stimulus-driven process, can also be governed by goal-directed mechanisms.     

Influence of Stimulus Salience and Attentional Demands on Visual Search Patterns in Hemispatial Neglect

Seventy-five left and right brain-damaged patients, with or without hemispatial neglect, and 40 age-matched control subjects were tested on cancellation tasks with two different visual textures modeled after Julesz (1981). In one condition (“preattentive”), target elements segregated easily from background elements and were perceived effortlessly. In the other (“attentive”), target elements did not segregate easily and could be detected only after prolonged focal scrutiny. Both controls and patients were more accurate and faster on the preattentive than attentive texture. However, only neglect patients were disproportionately impaired on the attentive texture, thus suggesting that unilateral neglect is exacerbated by the low visual salience of the stimuli and a higher engagement of focal attention. Thus, a simple bedside test may help to tell apart the level of visual information processing maximally impaired in neglect patients.     

Effects of surface texture and grip force on the discrimination of hand-held loads

In this paper, we report the results from two experiments in which subjects were required to discriminate horizontal load forces applied to a manipulandum held with a precision grip. The roughness (and hence friction) of the grip surfaces and required grip force were manipulated. In the first experiment, subjects were instructed to judge the load while maintaining hand position and not letting the manipulandum slip. It was found that performance was influenced by surface texture; a given load was judged to be greater when the surface texture was smooth than when it was rough. This result is consistent with a previous study based on lifting objects and indicates that the effect of surface texture applies to loads in general and not just to gravitational loads (i.e., weight). To test whether the load acting on a smooth object is judged to be greater because the grip force required to prevent it from slipping is larger, a second experiment was carried out. Subjects used a visual feedback display to maintain the same grip force for smooth and rough manipulandum surfaces. In this case, there was no effect of surface texture on load perception. These results provide evidence that perceived load depends on the grip force used to resist the load. The implications of these results in terms of central and peripheral factors underlying load discrimination are considered.     

On the interference of task-irrelevant hue variation on texture segmentation.

Although natural images often include discordant information about object boundaries, the majority of research on texture segmentation has involved variation along a single dimension, e.g. colour, orientation, size. In this study, we examined orientation-based texture segmentation in the presence and absence of task-irrelevant colour variation. Previously, it had been shown that orientation-based texture segmentation was impaired if the elements, normally of one colour, were randomly allocated one of two colours (Morgan et al, 1992 Proceedings of the Royal Society of London, Series B 248 291-295). We found that this interference disappeared, however, when the spatial pattern of the colour variation was regular, as opposed to random, and when the elements were randomly positioned. We consider four models of how relevant and irrelevant texture information might combine to produce the interference effect, with special regard to these new findings. None of the models could account for the dependency of the interference effect on the spatial arrangement of colour and orientation in the texture. We suggest that inter-element separation and spatial-frequency selectivity are critical variables in the interference effect.     

Separability and integrality of global and local levels of hierarchical patterns

We used a constrained classification task to examine the perceptual relations between global and local levels in hierarchical patterns composed of many, relatively small elements and those composed of few, relatively large elements. In Experiments 1 and 3 subjects were asked to make classifications based on "form" or "texture." In Experiments 2 and 4 they were asked to classify according to the "shape" of the configuration or the elements. The results indicate that configural and elemental levels are perceptually separable for many-element patterns when processed as form and texture: Subjects could attend to either level without being affected by variation along the irrelevant dimension. However, when the same many-element patterns were processed for global and local shape, subjects could not selectively attend to either level. For few-element patterns, global configuration and local elements appeared to be perceptually integral dimensions. These results are relevant to two issues: the global precedence hypothesis and the explanations of integral and separable dimensions.     

Disentangling Context Availability and Concreteness in Lexical Decision and W ord Translation

This study examines contrasting predictions of the dual coding theory and the context availability hypothesis regarding concreteness effects in monolingual and bilingual lexical processing. In three experiments, concreteness was controlled for or confounded with rated context availability. In the first experiment, bilingual subjects performed lexical decision in their native language (Dutch, L1). In the second experiment, lexical decision performance of bilinguals in their second language (English, L2) was examined. In the third experiment, bilinguals translated words 'forwards' (from L1 to L2) or 'backwards' (from L2 to L1). Both monolingual and bilingual tasks showed a concreteness effect when concreteness was confounded with context availability. However, concreteness effects disappeared when abstract and concrete words were matched on context availability, and even occasionally reversed. Implications of these results for theories that account for concreteness effects, particulary in bilingual processing, are discussed.     

A conceptual validation study of the texture response on the Rorschach.

This study addresses the Rorschach texture response (T). The authors proposed a developmental line incorporating tactile self-soothing functions and tactile aspects of interpersonal closeness and related it to T. It was hypothesized that T would be linearly related to one's reliance on tactile cues cognitively by categorizing objects according to texture and behaviorally by touching and stroking. Subjects were 81 women, between the ages of 18 and 30. The results confirm the notion that T is related to both cognitive and behavioral reliance on tactile cues. It was also hypothesized that high T subjects, more than others, would increase their use of tactile cues and touching when stressed, but this hypothesis was not supported. The results were considered to be consistent with the proposed developmental line but not for differential regression along the line. They also supported T as being related to a tactile mode of information processing.     

Explicit algebraic models for constructive and classical theories with non-standard elements

We describe an explicit construction of algebraic models for theories with non-standard elements either with classical or constructive logic. The corresponding truthvalue algebra in our construction is a complete algebra of subsets of some concrete decidable set. This way we get a quite finitistic notion of true which reflects a notion of the deducibility of a given theory. It enables us to useconstructive, proof-theoretical methods for theories with non-standard elements. It is especially useful in the case of theories with constructive logic where algorithmic properties are essential.The research was supported partly by the Hungarian National Fundation for Scientific Research No. 1654.     

Perceptual organization and attention

It is widely assumed that the grouping of the visual field first described by the Gestalt psychologists and the related phenomenon of texture segregation occur very early in the processing of visual information and involve preattentive processes. All the recent evidence supporting this assumption comes from visual search experiments in which the subject is actively looking for a target and attending to the stimulus. The question at issue is whether these kinds of patterns are perceived under conditions of inattention, i.e., when observers are not searching for them. We performed six experiments to determine whether texture segregation and grouping by similarity or proximity are perceived under conditions of inattention. On the first two trials subjects were asked to report the longer arm of a briefly presented cross which was surrounded by a pattern of ungrouped small elements. On the third trial and subsequent control trials these elements were configured into grouping patterns and subjects queried about them immediately following their line length reports. The results establish that neither texture segregation nor grouping by similarity of lightness or proximity are perceived under conditions of inattention. They support the conclusion that there is an earlier stage of processing than that referred to as preattentive.     

A Conceptual Validation Study of the Texture Response on the Rorschach

This study addresses the Rorschach texture response (T). The authors proposed a developmental line incorporating tactile self-soothing functions and tactile aspects of interpersonal closeness and related it to T. It was hypothesized that T would be linearly related to one's reliance on tactile cues cognitively by categorizing objects according to texture and behaviorally by touching and stroking. Subjects were 81 women, between the ages of 18 and 30. The results confirm the notion that T is related to both cognitive and behavioral reliance on tactile cues. It was also hypothesized that high T subjects, more than others, would increase their use of tactile cues and touching when stressed, but this hypothesis was not supported. The results were considered to be consistent with, the proposed developmental line but not for differential regression along the line. They also supported T as being related to tactile mode of information processing.     

Visual marking beside the mark: Prioritizing selection by abrupt onsets

In a standard visual marking experiment, observers are presented with a display containing one set of elements (old elements) followed after a certain time interval by a second set of elements (new elements). The task of observers is to search for a target among the new elements. Typically, the time to find the target depends only on the number of new elements in the display and not on the number of old elements, showing that observers search only among the new elements. This effect of prioritizing new elements over old elements is explained in terms of top-down inhibition of old objects—that is, visual marking (Watson & Humphreys, 1997). The present study addressed whether this prioritizing is in fact mediated by top-down inhibition of old objects, as suggested by Watson and Humphreys (1997), or whether it is mediated by the abrupt onsets of the newly presented elements (Yantis & Jonides, 1984). In three experiments, the presentations of the old and new elements were or were not accompanied by a luminance change. The results showed that if new elements were equiluminant with the background, no visual marking occurred, suggesting that new elements must have a luminance onset in order to be prioritized over old elements. Implications for current theories on visual selection are discussed.     

Visual marking beside the mark: prioritizing selection by abrupt onsets

In a standard visual marking experiment, observers are presented with a display containing one set of elements (old elements) followed after a certain time interval by a second set of elements (new elements). The task of observers is to search for a target among the new elements. Typically, the time to find the target depends only on the number of new elements in the display and not on the number of old elements, showing that observers search only among the new elements. This effect of prioritizing new elements over old elements is explained in terms of top-down inhibition of old objects-that is, visual marking (Watson & Humphreys, 1997). The present study addressed whether this prioritizing is in fact mediated by top-down inhibition of old objects, as suggested by Watson and Humphreys (1997), or whether it is mediated by the abrupt onsets of the newly presented elements (Yantis & Jonides, 1984). In three experiments, the presentations of the old and new elements were or were not accompanied by a luminance change. The results showed that if new elements were equiluminant with the background, no visual marking occurred, suggesting that new elements must have a luminance onset in order to be prioritized over old elements. Implications for current theories on visual selection are discussed.     

The effect of texture relief on perception of slant from texture

Texture can be an effective source of information for perception of slant and curvature. A computational assumption required for some texture cues is that texture must be flat along a surface. There are many textures which violate this assumption, and have some sort of texture relief: variations perpendicular to the surface. Some examples include grass, which has vertical elements, or scattered rocks, which are volumetric elements with 3-D shapes. Previous studies of perception of slant from texture have not addressed the case of textures with relief. The experiments reported here test judgments of slant for textures with various types of relief, including textures composed of bumps, columns, and oriented elements. The presence of texture relief was found to affect judgments, indicating that perception of slant from texture is not robust to violations of the flat-texture assumption. For bumps and oriented elements, slant was underestimated relative to matching flat textures, while for columns textures, which had visible flat top faces, perceived slant was equal or greater than for flat textures. The differences can be explained by the way different types of texture relief affect the amount of optical compression in the projected image, which would be consistent with results from previous experiments using cue conflicts in flat textures. These results provide further evidence that compression contributes to perception of slant from texture.     

Semantic grounding in models of analogy: an environmental approach

Empirical studies indicate that analogy consists of two main processes: retrieval and mapping. While current theories and models of analogy have revealed much about the mainly structural constraints that govern the mapping process, the similarities that underpin the correspondences between individual representational elements and drive retrieval are understood in less detail. In existing models symbol similarities are externally defined but neither empirically grounded nor theoretically justified. This paper introduces a new model (EMMA: the environmental model of analogy) which relies on co‐occurrence information provided by LSA (Latent Semantic Analysis; Landauer & Dumais, 1997) to ground the relations between the symbolic elements aligned in analogy. LSA calculates a contextual distribution for each word encountered in a corpus by counting the frequency with which it co‐occurs with other words. This information is used to define a model that locates each word encountered in a high‐dimensional space, with relations between elements in this space representing contextual similarities between words. A series of simulation experiments demonstrate that the environmental approach to semantics embodied in LSA can produce appropriate patterns of analogical retrieval, but that this semantic measure is not sufficient to model analogical mapping. The implications of these findings, both for theories of representation in analogy research and more general theories of semantics in cognition, are explored.     

Figure-background perception in right and left hemispheres of human commissurotomy subjects

The right and left hemispheres of four complete commissurotomy subjects were tested for the ability to recognize and integrate figure and background elements of composite visual stimuli. In the first experiment the subjects were required to identify from a four-choice array in free vision the stimulus card that matched the briefly lateralized sample stimulus. For all subjects the left hemispheres was proficient at identifying the figure, but performed at near-chance level in recognizing the textured background. In contrast, the right hemisphere was equally adapt at identifying figures and backgrounds. Both hemispheres could easily identify the isolated figure or background from a choice array, demonstrating that the observed hemisphere effects were due to figure-background interactions rather than the result of any difficulty in processing specific elements of the composite stimulus. The second experiment involved the determination of the size and position of a dot that appeared against various plain and textured backgrounds. The right hemisphere of two subjects, but not the left, performed with greater accuracy when the background consisted of a 'natural' texture gradient rather than a plain white backing. Similar though less consistent results were obtained when an inverted gradient or an evenly spaced grid was used as the background. For each condition, right-hemisphere performance resembled that of normal control subjects. In contrast, the left hemisphere provided a pattern of results dissimilar to that of control subjects for the various figure-background tasks described. It appeared to be generally insensitive to background effects, except when the information provided by the background was highly unusual, as from an inverted texture gradient. The results suggest a preeminent role for the right hemisphere in the recognition of background components of a whole-field stimulus, sensitivity to the influence of the background on the perception of an object, and the ability to use natural perspective cues to assist in the accurate perception of an object.     

PUNISHMENT IN HUMAN CHOICE: DIRECT OR COMPETITIVE SUPPRESSION?

This investigation compared the predictions of two models describing the integration of reinforcement and punishment effects in operant choice. Deluty's (1976) competitive-suppression model (conceptually related to two-factor punishment theories) and de Villiers' (1980) direct-suppression model (conceptually related to one-factor punishment theories) have been tested previously in nonhumans but not at the individual level in humans. Mouse clicking by college students was maintained in a two-alternative concurrent schedule of variable-interval money reinforcement. Punishment consisted of variable-interval money losses. Experiment 1 verified that money loss was an effective punisher in this context. Experiment 2 consisted of qualitative model comparisons similar to those used in previous studies involving nonhumans. Following a no-punishment baseline, punishment was superimposed upon both response alternatives. Under schedule values for which the direct-suppression model, but not the competitive-suppression model, predicted distinct shifts from baseline performance, or vice versa, 12 of 14 individual-subject functions, generated by 7 subjects, supported the direct-suppression model. When the punishment models were converted to the form of the generalized matching law, least-squares linear regression fits for a direct-suppression model were superior to those of a competitive-suppression model for 6 of 7 subjects. In Experiment 3, a more thorough quantitative test of the modified models, fits for a direct-suppression model were superior in 11 of 13 cases. These results correspond well to those of investigations conducted with nonhumans and provide the first individual-subject evidence that a direct-suppression model, evaluated both qualitatively and quantitatively, describes human punishment better than a competitive-suppression model. We discuss implications for developing better punishment models and future investigations of punishment in human choice.     

Discrimination of higher-order textures

Arrays of figural elements differing in certain features ('textons') may be visually segregated to yield the impression of a global figure of different texture. This fact was used to construct texture patterns of a higher level of complexity. In microstructure, these patterns reveal regular arrays of distinguishable figural elements, the segregation of which can be predicted from previous studies of human texture sensitivity. In macrostructure, clusters of such elements form new figural elements which, when repeated over space, themselves give the impression of texture at a perceptually higher level. Discrimination of such macrostructure textures was found to place similar restrictions on the form of figural elements as those of texture discrimination at the microstructure level.     

Constraints on Analogical Mapping: A Comparison of Three Models

Three theories of analogy have been proposed that are supported by computational models and data from experiments on human analogical abilities. In this article we show how these theories can be unified within a common metatheoretical framework that distinguishes among levels of informational, behavioral, and hardware constraints. This framework clarifies the distinctions among three computational models in the literature: the Analogical Constraint Mapping Engine (ACME), the Structure-Mapping Engine (SME), and the Incremental Analogy Machine (IAM). We then go on to develop a methodology for the comparative testing of these models. In two different manipulations of an analogical mapping task we compare the results of computational experiments with these models against the results of psychological experiments. In the first experiment we show that increasing the number of similar elements in two analogical domains decreases the response time taken to reach the correct mapping for an analogy problem. In the second psychological experiment we find that the order in which the elements of the two domains are presented has significant facilitative effects on the ease of analogical mapping. Of the three models, only IAM embodies behavioral constraints and predicts both of these results. Finally, the immediate implications of these results for analogy research are discussed, along with the wider implications the research has for cognitive science methodology.     

Visual aftereffect of texture density contingent on color of frame

An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow’s (1990) model of modifiable inhibition.