Event structure in perception and conception

Events can be understood in terms of their temporal structure. The authors first draw on several bodies of research to construct an analysis of how people use event structure in perception, understanding, planning, and action. Philosophy provides a grounding for the basic units of events and actions. Perceptual psychology provides an analogy to object perception: Like objects, events belong to categories, and, like objects, events have parts. These relationships generate 2 hierarchical organizations for events: taxonomies and partonomies. Event partonomies have been studied by looking at how people segment activity as it happens. Structured representations of events can relate partonomy to goal relationships and causal structure; such representations have been shown to drive narrative comprehension, memory, and planning. Computational models provide insight into how mental representations might be organized and transformed. These different approaches to event structure converge on an explanation of how multiple sources of information interact in event perception and conception.     

Evidence for a basic level in event taxonomies

The proposition that event taxonomies have a “basic” level was tested. In the first two tasks of the experiment, taxonomically related event categories were elicited. Nine taxonomies were constructed from subjects’ responses on these tasks. In the third task, subjects listed attributes for events categories from the three levels of abstraction of these taxonomies. A single, common level of abstraction (the basic level) was identified. Subjects listed significantly more attributes for basic categories than for superordinate categories, but not significantly more attributes for the lower, subordinate-level categories. Further analyses showed that basic and subordinate categories elicited a greater number of concrete and event-related features than action and personrelated features, and that superordinate categories showed the opposite trend. These findings are discussed in terms of general principles of categorization applied to events, objects, and scenes, and the particular characteristics of events.     

Basic objects in natural categories

Categorizations which humans make of the concrete world are not arbitrary but highly determined. In taxonomies of concrete objects, there is one level of abstraction at which the most basic category cuts are made. Basic categories are those which carry the most information, possess the highest category cue validity, and are, thus, the most differentiated from one another. The four experiments of Part I define basic objects by demonstrating that in taxonomies of common concrete nouns in English based on class inclusion, basic objects are the most inclusive categories whose members: (a) possess significant numbers of attributes in common, (b) have motor programs which are similar to one another, (c) have similar shapes, and (d) can be identified from averaged shapes of members of the class. The eight experiments of Part II explore implications of the structure of categories. Basic objects are shown to be the most inclusive categories for which a concrete image of the category as a whole can be formed, to be the first categorizations made during perception of the environment, to be the earliest categories sorted and earliest named by children, and to be the categories most codable, most coded, and most necessary in language.     

Categories of environmental scenes

Environmental scenes are the settings in which human action occurs; since they constrain behavior, they are of interest to social, personality, and environmental psychologists. Scenes can also be viewed as a spatial generalization of objects, as well as the spatial contexts in which objects appear. As such, they are studied in perception and memory. Previous approaches to characterizing environments have relied on scaling techniques to yield a manageable number of dimensions or attributes by which environments can be compared. In contrast, the present research demonstrates development of a taxonomy of kinds of environmental scenes, where perceived attributes are obtained as a byproduct. A basic or preferred level of categorization in the taxonomy is also identified, based on measures of cognition, behavior, and communication. The basic level, for example, school, home, beach, mountains, corresponds to the level commonly used in the study of scene schemas in perception, memory, and environmental psychology, as well as to the level apparently most useful in other domains of knowledge concerned with environments, for example, architecture and geography.     

Interactive processing among parts, configuration, and orientation of complex objects

The aim of the present study was to investigate whether the representation of parts and the configuration and orientation of complex objects were separate or interdependent. Participants were asked to match parts and configuration of novel 3-D objects with constant or varied features in irrelevant dimensions. The results of both Exp. 1 (sequential matching) and Exp. 2 (simultaneous matching) showed that both sensitivity and response time (RT) of part matching were influenced by whether the irrelevant configuration remained constant or varied. Both sensitivity and RT for configuration matching were affected by the variation of irrelevant parts in Exp. 2, but only sensitivity was affected in Exp. 1. These results demonstrated an interdependent pattern of representations of parts and relations but different interactive patterns in memory and perception. The results of Exp. 3 showed orientation dependency in a configuration-matching task but orientation invariance in a part-matching task. Consistent with a study done in 2000 by Edelman and Intrator, these results suggest an interactive processing between configuration and orientation but an independent processing between the parts and orientation.     

Parts and the basic level in natural categories and artificial stimuli: Comments on Murphy (1991)

Natural taxonomies consist of categories that vary in level of abstraction. Categories at the basic level, such as chair and apple, are preferred in a broad range of situations (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). Several studies have revealed qualitative differences between the basic level and other levels. For example, Tversky and Hemenway (1984) presented evidence that parts proliferative at the basic level; they proposed that parts link the appearance of category members with their functions. Although not taking issue with these findings, Murphy (1991) investigated whether parts are necessary or sufficient for a basic level. In an attempt to demonstrate that parts are not necessary, Murphy used artificial stimuli that did not capture the essential features of natural taxonomies. These discrepancies preclude any conclusions based on his studies. Murphy's data also do not support his claim that parts are not sufficient for a basic level. Finally, it is unlikely that pursuing questions of necessity or sufficiency will produce insights into human categorization.     

Parts function as perceptual organizational entities in infancy

Both objects and parts function as organizational entities in adult perception. Prior research has indicated that objects affect organization early in life: Infants grouped elements located within object boundaries and segregated them from those located on different objects. Here, we examined whether parts also induce grouping in infancy. Five- and 6.5-month-olds were habituated to two-part objects containing element pairs. In a subsequent test, infants treated groupings of elements that crossed part boundaries as novel, in comparison with groupings that had shared a common part during habituation. In contrast, the same arrangement of elements failed to elicit evidence of grouping in control conditions in which the elements were not surrounded by closed part boundaries. Thus, infants grouped and segregated elements on the basis of part structure. Part-based processing is a key aspect of many theories of perception. The present research adds to this literature by indicating that parts function as organizational entities early in life.     

Parts, cavities, and object representation in infancy

Part representation is not only critical to object perception but also plays a key role in a number of basic visual cognition functions, such as figure-ground segregation, allocation of attention, and memory for shapes. Yet, virtually nothing is known about the development of part representation. If parts are fundamental components of object shape representation early in life, then the infant visual system should give priority to parts over other aspects of objects. We tested this hypothesis by examining whether part shapes are more salient than cavity shapes to infants. Five-month-olds were habituated to a stimulus that contained a part and a cavity. In a subsequent novelty preference test, 5-month-olds exhibited a preference for the cavity shape, indicating that part shapes were more salient than cavity shapes during habituation. The differential processing of part versus cavity contours in infancy is consistent with theory and empirical findings in the literature on adult figure-ground perception and indicates that basic aspects of part-based object processing are evident early in life.     

Spatial habit competes with effort to determine human spatial organization

Despite the important role that the physical environment plays in shaping human cognition, few studies have endeavoured to experimentally examine the principles underlying how individuals organize objects in their space. The current investigation examines the idea that humans organize objects in their space in order to minimize effort or maximize performance. We devised a novel spatial organization task whereby participants freely arranged objects in the context of a writing task. Critically, we manipulated the frequency with which each object was used and assessed participants’ spontaneous placements. In the first set of experiments, participants showed a counterintuitive tendency to match pen pairs with their initial placements rather than placing pens in the less effortful configuration. However, in Experiment 2, where the difference in physical effort between different locations was increased, participants were more likely to reorganize the pens into the less effortful configuration. We begin developing a theory of human spatial organization wherein the observed initial bias may represent a kind of spatial habit formation that competes with effort/performance considerations to shape future spatial organization.     

The Tree of Life: Universal and Cultural Features of Folkbiological Taxonomies and Inductions

Two parallel studies were performed with members of very different cultures—industrialized American and traditional Itzaj-Mayan—to investigate potential universal and cultural features of folkbiological taxonomies and inductions. Specifically, we examined how individuals organize natural categories into taxonomies, and whether they readily use these taxonomies to make inductions about those categories. The results of the first study indicate that there is a cultural consensus both among Americans and the Itzaj in their taxonomies of local mammal species, and that these taxonomies resemble and depart from a corresponding scientific taxonomy in similar ways. However, cultural differences are also shown, such as a greater differentiation and more ecological considerations in Itzaj taxonomies. In a second study, Americans and the Itzaj used their taxonomies to guide similarity- and typicality-based inductions. These inductions converge and diverge crossculturally and regarding scientific inductions where their respective taxonomies do. These findings reveal some universal features of folkbiological inductions, but they also reveal some cultural features such as diversity-based inductions among Americans, and ecologically based inductions among the Itzaj. Overall, these studies suggest that while building folkbiological taxonomies and using them for folkbiological inductions is a universal competence of human cognition there are also important cultural constraints on that competence.     

Temporal organization of pattern structure

Two pattern reproduction experiments examined the relations among the figural goodness of a pattern, the organization of two parts within the pattern, and the interpart interval (ISI), which ranged from 40 to 200 msec. If the parts contained connected line segments, performance was slightly better (3%-5% gain in accuracy) at a 40-msec ISI than at a 200-msec ISI. If the parts contained unconnected line segments, reproduction accuracy of the first part declined sharply between 40 and 200 msec. These results were interpreted by assuming that the parts were perceived as a single whole pattern at a 40-msec ISI but as two separate patterns at a 200-msec ISI. One surprising finding, the lack of an interaction between figural goodness and ISI, was explained in terms of a response bias in favor of figural good patterns. A secondary manipulation revealed that a part was more accurately reproduced in a good figure context than in a poor figure context but was most accurately reproduced when it appeared alone.     

Selective attention to the parts of an object

Recent empirical results suggest that there is a decrement in dividing attention between two objects in a scene compared with focusing attention on a single object. However, objects can be made of individual parts. Is there a decrement for dividing attention across different parts of a single object? We addressed this question in two experiments. In Experiment 1, we demonstrated that attention can exhibit part-based selection—that is, the subjects were more accurate in reporting two attributes from the same part of an object than they were in reporting attributes from different parts of an object. In Experiment 2, we demonstrated that part-based attentional decrements occurred simultaneously with object-based attentional decrements. The results from Experiment 2 demonstrated that part-based attention is evident at the same time as objects are processed as coherent wholes. Our results imply that there is an attentional mechanism that can select either objects or their parts.     

Visual object agnosia as a problem in integrating parts and part relations

Current models of vision generally assume that the recognition of visual objects is achieved by encoding their component parts, as well as the spatial relations among parts. The current study examined how the processing of parts and their configurations may be affected in visual agnosia due to brain damage. Both a visual agnosic patient (AR) and healthy control subjects performed a visual search task in which they had to discriminate between targets and distractors that varied according to whether they shared their parts and/or their configuration. The results show that AR's visual search rates are disproportionally slow when targets and distractors share the same configuration than when they have different configurations. AR is also found to be disproportionately slow in discriminating targets and distractors that share identical parts when the targets and distractors share the same configuration. With differently configured targets and distractors, AR shows no part sharing effect. For controls, in contrast, the part and configuration sharing effects occur independently of one another. It is concluded that AR's object recognition deficit arises from difficulties in discriminating objects that share their configuration, and from an abnormal dependency of part information processing upon object configuration.     

Embodied perception of reachable space: how do we manage threatening objects?

This study aimed at determining whether the size of reachable space is affected by the level of danger of some everyday manipulable objects. Two possibilities are examined: Dangerous objects affect the size of reachable space because of long-term semantic knowledge of their potential hurtful value or the on-line relation between objects’ dangerous attributes and the body. The experimental paradigm combined the danger value (dangerous/not dangerous) and the orientation of objects (e.g. pointing away from/towards the perceiver). Reachability judgments measured the size of peripersonal space, and perception of objects’ danger was estimated through questionnaires. Results revealed that, whatever the estimated level of objects’ danger, the extent of peripersonal space was reduced when the threatening part of dangerous objects was oriented towards participants, not when oriented away. This suggests that the characteristics of the here and now body-objects interaction are crucial in affecting the boundary of peripersonal space.     

Parts in object concepts: Experiments with artificial categories

Previous research has demonstrated that basic-level categories are associated with the parts of objects. Five experiments were conducted to investigate whether this correlation is caused by a psychological principle that requires basic concepts to have common parts. This hypothesis was investigated in the experiments by separating part and nonpart information in artificial categories. Basic-level structure was measured in two ways: as the level with the highest ratio of within-category similarity to between-category similarity, and as the level with the fastest categorization time in an object-identification task. The results revealed that basic-level structure could be found in categories that did not have parts in common. Furthermore, nonpart information, such as size, color, and texture, could both enhance the basic level and eliminate the basic-level advantage, depending on whether the nonpart information was consistent with or contradicted the part information. These results suggest that, psychologically, parts are neither necessary nor sufficient to form a basic level.     

A Study of Perceptual Analysis in a High-Level Autistic Subject with Exceptional Graphic Abilities

We report here the case study of a patient (E.C.) with an Asperger syndrome, or autism with quasinormal intelligence, who shows an outstanding ability for three-dimensional drawing of inanimate objects (savant syndrome). An assessment of the subsystems proposed in recent models of object recognition evidenced intact perceptual analysis and identification. The initial (or primal sketch), viewer-centered (or 2-1/2-D). or object-centered (3-D) representations and the recognition and name levels were functional. In contrast. E.C.′s pattern of performance in three different types of tasks converge to suggest an anomaly in the hierarchical organization of the local and global parts of a figure: a local interference effect in incongruent hierarchical visual stimuli, a deficit in relating local parts to global form information in impossible figures, and an absence of feature-grouping in graphic recall. The results are discussed in relation to normal visual perception and to current accounts of the savant syndrome in autism.     

Independent processing of parts and of their spatial organization in complex visual objects

A visual search experiment using synthetic three-dimensional objects is reported. The target shared its constituent parts, the spatial organization of its parts, or both with the distractors displayed with it. Sharing of parts and sharing of spatial organization both negatively affected visual search performance, and these effects were strictly additive. These findings support theories of complex visual object perception that assume a parsing of the stimulus into its higher-order constituents (volumetric parts or visible surfaces). The additivity of the effects demonstrates that information on parts and information on spatial organization are processed independently in visual search.     

Converging operations on a basic level in event taxonomies

Research on object concepts has identified one level of abstraction as "basic" in cognition and communication. We investigated whether concepts for routine social events have a basic level by replicating the converging operations used to investigate object concepts. In Experiment 1, subjects were presented with event names from a taxonomy and were asked to list the actions comprising the event. Many more actions were listed at the middle than at the highest taxonomic level, without a further increase at the most specific level, paralleling the pattern of superordinate-, basic-, and subordinate-level object concepts. From these action lists, brief stories were composed for each event. In Experiment 2, subjects made pairwise similarity judgments on the stories. The mean similarity of events increased with specificity, as expected. But differentiation of categories (within-category similarity compared to between-category similarity) was highest for super-ordinates, contrary to results with object categories. In Experiment 3, subjects were fastest in recognizing actions as belonging to events named at the basic level. In Experiment 4, subjects predominantly chose basic-level terms to name stories. We conclude that event taxonomies do show basic-level structure, albeit a less sharply defined and less stable structure than in object taxonomies. The benefits and hazards of extending models of object concepts to other entities, such as social events, are discussed.