Theories of visual pattern recognition frequently assume that processing begins with an analysis of the pattern into component parts, which are often assumed to be line segments of particular orientations, lengths, positions, and curvatures. The present experiments measured discriminability of these simple parts when presented either in isolation or within configural contexts that provided no formal information useful for the discrimination. Certain contexts either impaired or did not affect performance. Other contexts were found, however, which dramatically improved discriminability. Thus, two patterns which differed only in a single part could be discriminated from each other more quickly than could their distinguishing parts shown in isolation. Further experiments suggest that this "configural superiority" effect influences perceptual components of processing rather than memorial components. The mechanism underlying configural superiority appears to be the detection of novel and distinguishing features, such as corners and intersections, which emerge when parts are placed in close proximity to each other. The outlines of a model for preattentive feature discrimination are presented.Many models of pattern recognition assume that processing begins with an analysis of the stimulus into its component features, parts, or dimensions. While specific models differ in how feature analysis takes place (e.g., in serial or parallel) and in which particular features are analyzed, the central idea is that the identity of a pattern can be deduced from knowledge of its component parts and, perhaps, the structural relations among them (

This study explores the perception of stimuli at two levels: local parts and the wholes that comprise these parts. Previous research has produced contradictory results. Some studies (e.g., Pomerantz & Sager, 1975) show local precedence, in which the local parts are more difficult to ignore in selective attention tasks. Other studies (e.g., Navon, 1977) have shown the opposite effect, global precedence. The present five experiments trace the causes of this discrepancy by exploring the effects of the relative discriminabilities of the local and global levels of the stimuli and the differences between two different measures of selective attention, namely, Stroop-type interference (attributable to incongruity on the irrelevant dimension) and Garner-type interference (attributable to variability on the irrelevant dimension). The experiments also examine whether the precedence effects previously examined in form perception generalize to motion perception. The results show that (a) some cases of global precedence are due solely to the greater perceptual discriminability of the global level and thus demonstrate only that more discriminable stimuli are harder to ignore; (b) instances of both local and global precedence can be demonstrated for certain types of stimuli, even when the discriminabilities of their local and global levels have been equated; and (c) the Stroop and Garner measures of selective attention are not equivalent but instead measure different types of interference. In addition, a distinction is made between two fundamentally different types of part-whole relationships that exist in visual configurations, one based only on the positions of the parts (Type P) and one based also on the nature of the parts (Type N). Previous research has focused on Type P, which appears to be irrelevant to the broader questions of Gestalt and top-down effects in perception. It is concluded that bona fide cases of both local and global precedence have been amply documented but that no general theory can account for why or when these effects will appear until we better understand both the nature of part-whole relationships and the perceptual processes that are tapped by different measures of selective attention.

Our first review paper on the occasion of the centennial anniversary of Gestalt psychology focused on perceptual grouping and figure-ground organization. It concluded that further progress requires a reconsideration of the conceptual and theoretical foundations of the Gestalt approach, which is provided here. In particular, we review contemporary formulations of holism within an information-processing framework, allowing for operational definitions (e.g., integral dimensions, emergent features, configural superiority, global precedence, primacy of holistic/configural properties) and a refined understanding of its psychological implications (e.g., at the level of attention, perception, and decision). We also review four lines of theoretical progress regarding the law of Prägnanz—the brain’s tendency of being attracted towards states corresponding to the simplest possible organization, given the available stimulation. The first considers the brain as a complex adaptive system and explains how self-organization solves the conundrum of trading between robustness and flexibility of perceptual states. The second specifies the economy principle in terms of optimization of neural resources, showing that elementary sensors working independently to minimize uncertainty can respond optimally at the system level. The third considers how Gestalt percepts (e.g., groups, objects) are optimal given the available stimulation, with optimality specified in Bayesian terms. Fourth, Structural Information Theory explains how a Gestaltist visual system that focuses on internal coding efficiency yields external veridicality as a side-effect. To answer the fundamental question of why things look as they do, a further synthesis of these complementary perspectives is required.

The possibility that perceptual configuration of stimulus elements impairs the ability to attend selectively to individual elements was tested with two-element stimuli. constructed by placing two curved lines in close proximity. Ss rapidly classified series of these stimuli which could differ on both elements or on only one with the second held constant. It was hypothesized that if the two elements formed a configuration, then Ss should have difficulty attending selectively to the element relevant for classification while filtering information from the other element. This result was obtained in one experiment with both stimulus elements oriented vertically, and it is concluded that these stimuli were perceived as unanalyzed, nominally related shapes. In another experiment, with one stimulus element oriented horizontally. selective attention to the relevant element was possible.

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We examined the grouping of line segments into unitary shapes and attempted to identify procedures to diagnose when such grouping is taking place. Previous research has indicated that attentional measures may diagnose grouping: With grouped parts, selective attention to individual parts is difficult and divided attention across parts is easy, whereas with ungrouped parts selective attention is easy and divided attention is difficult. This result suggests that grouping operates via a perceptual glue binding parts into wholes that are difficult or impossible to divide. Other studies have suggested in addition that grouped parts produce emergent features, possibly including symmetry and closure, that make possible configural superiority effects, where whole shapes are more discriminable than are their distinguishing contours shown in isolation. The 13 experiments reported here indicate that perceptual glue is not needed to explain known findings about grouping, a claim that agrees with conclusions by other investigators using other criteria. Rather, emergent features alone may suffice to explain grouping, provided that reliable and accurate diagnostic criteria can be identified. It is shown that the diagnostics now available are not fully adequate for this purpose. Surprisingly, it appears that some prime candidates for emergent features--namely, closure and line terminators--may not be of central importance to form perception.

Gestalt phenomena are often so powerful that mere demonstrations can confirm their existence, but Gestalts have proven hard to define and measure. Here we outline a theory of basic Gestalts (TBG) that defines Gestalts as emergent features (EFs). The logic relies on discovering wholes that are more discriminable than are the parts from which they are built. These wholes contain EFs that can act as basic features in human vision. As context is added to a visual stimulus, a hierarchy of EFs appears. Starting with a single dot and adding a second yields the first two potential EFs: the proximity (distance) and orientation (angle) between the two dots. A third dot introduces two more potential EFs: symmetry and linearity; a fourth dot produces surroundedness. This hierarchy may extend to collinearity, parallelism, closure, and more. We use the magnitude of Configural Superiority Effects to measure the salience of EFs on a common scale, potentially letting us compare the strengths of various grouping principles. TBG appears promising, with our initial experiments establishing and quantifying at least three basic EFs in human vision.

The role of element proximity in perceptual grouping was examined in tasks requmng speeded discrimination of two-element visual patterns. Grouping of two elements was defined as the failure of attention to be focused on one element selectively in filtering tasks where only that one element was relevant to the discrimination. Failure of selective attention was measured by the degree of interference caused by variation of the irrelevant element. Grouping was shown to diminish monotonically as the spacing between two elements was increased. At a given spacing, grouping could be reduced or eliminated by the introduction of a third element into the stimulus field, presumably because the addition of this element triggered a reorganization of the perceptual field into a new grouping structure. Grouping appeared to facilitate performance on condensation tasks requiring distributed attention, to the degree that the condensation tasks were actually easier than the filtering tasks at close proximities. Paradoxically, for some tasks, moving an irrelevant element away from a relevant one actually impaired performance, suggesting that paying attention to irrelevant information could be beneficial. This result, if generalizable, suggests that grouping be conceptualized not as an automatic process under preattentive control but as an optional process under strategic control. This paper is concerned with two aspects of the problem 01 perceptual organization of visual arrays (Wertheimer, 1923). The first is the degree to which perceptual organization is under the control of specitic parameters of the stimulus array, as opposed to cognitive (strategic) factors within the observer. The second is the establishment of experimental measures of organizational processes. This latter issue is much more than simply a methodological one, for in order to measure organization a theory is required that explains just what organization means, and how and where organization enters into the processing of perceptual information.The Gestalt "laws" of course represented an attempt to answer the first question. Certain stimulus variables. some well defined (proximity) and some not so well defined (similarity), can be shown to have clear effects on the wayan observer reports his perception of stimulus arrays. The conclusions one can draw from these demonstrations. as compelling as the perceptual effects may be, are limited, however. to the domain of phenomenology and say little about the underlying processes that shape our perceptual experiences. What is required are performance measures. rather than subjective reports. of perceptual organization. Pomerantz and Garner (1973) argued that if organization is more than an epiphenomenon. there