Bennett I. Bertenthal

Global Processing of Biological Motions

The structure of the human form is quickly and unequivocably recognized from 10 to 13 points of light moving as if attached to the major joints and head of a person walking Recent psychophysical and computational models of this process suggest that these displays are organized by low-level processing constraints that delimit the pair-wise connections of the point lights In the current research, these low-level constraints were rendered uninformative by a masking paradigm The results from four experiments converged to show that the perception of structure in a point-light walker display does not require the prior detection of individual features or local relations

Haste does not always make waste: Expertise, direction of attention, and speed versus accuracy in performing sensorimotor skills

In two experiments, we examined the attentional mechanisms governing sensorimotor skill execution across levels of expertise. In Experiment 1, novice and expert golfers took a series of putts under dual-task conditions designed to distract attention from putting and under skill-focused conditions that prompted attention to step-by-stePperformance. Novices performed better under skill-focused than under dual-task conditions. Experts showed the opposite pattern. In Experiment 2, novice and expert golfers putted under instructions that emphasized either putting accuracy or speed—the latter intended to reduce the time available to monitor and explicitly adjust execution parameters. Novices putted better under accuracy instructions. Experts were more accurate under speed instructions. In agreement with theories of skill acquisition and automaticity, novice performance is enhanced by conditions that allow for on-line attentional monitoring (e.g., skill-focused or accuracy instructions) in comparison with conditions that prevent explicit attentional control of skill execution (e.g., dual-task or speed constraints). In contrast, the proceduralized skill of experts benefits from environments that limit, rather than encourage, attention to execution.

Infant sensitivity to figural coherence in biomechanical motions

Two experiments assessed infant sensitivity to figural coherence in point-light displays moving as if attached to the major joints of a walking person. Experiment 1 tested whether 3- and 5-month-old infants could discriminate between upright and inverted versions of the walker in both moving and static displays. Using an infant-control habituation paradigm, it was found that both ages discriminated the moving but not the static displays. Experiment 2 was designed to clarify whether or not structural invariants were extracted from these displays. The results revealed that (1) moving point-light displays with equivalent motions but different topographic relations were discriminated while (2) static versions were not, and (3) arrays that varied in the amount of motion present in different portions of the display were also not discriminated. These results are interpreted as indicating that young infants are sensitive to figural coherence in displays of biomechanical motion.

Imitative response tendencies following observation of intransitive actions

Clear and unequivocal evidence shows that observation of object affordances or transitive actions facilitates the activation of a compatible response. By contrast, the evidence showing response facilitation following observation of intransitive actions is less conclusive because automatic imitation and spatial compatibility have been confounded. Three experiments tested whether observation of a finger movement (i.e., an intransitive action) in a choice reaction-time task facilitates the corresponding finger movement response because of imitation, a common spatial code, or some combination of both factors. The priming effects of a spatial and an imitative stimulus were tested in combination (Experiment 1), in opposition (Experiment 2), and independently (Experiment 3). Contrary to previous findings, the evidence revealed significant contributions from both automatic imitation and spatial compatibility, but the priming effects from an automatic tendency to imitate declined significantly across a block of trials whereas the effects of spatial compatibility remained constant or increased slightly. These differential effects suggest that priming associated with automatic imitation is mediated by a different regime than priming associated with spatial compatibility.

Eye, head and trunk control : The foundation for manual development

Mastery of reaching and manipulation relies on adequate postural control. The trunk must be balanced relative to a base of support to allow free movements of the arms and hands. Moreover, the head must be supported flexibly by the trunk so that gaze can be directed toward the target to provide a spatial frame of reference for reaching. For fine manipulation it is also crucial to avoid retinal slips which would introduce blur. Stabilizing gaze is generally accomplished through adjustments of both eye and head position. Until gaze is stabilized, it is difficult to establish a frame of reference between the target and the self. Thus, a nested hierarchy of support involving the eyes, head, and trunk forms an important foundation for manual activity.

Perception and Action

All spatially and temporally coordinated behaviors are organized as action systems involving the coupling of perception and action. Some action systems are present at birth, but most will develop in the months and years to come; all of them will become better coordinated and tuned as a function of both neural development and experience. A number of key principles for explaining how perception and action are coupled are presented with specific examples from infant development, and followed by a discussion of specific change mechanisms responsible for the development of action systems.

Early Experience and Emotional Development: The Emergence of Wariness of Heights

Because of its biological adaptive value, wariness of heights is widely believed to be innate or under maturational control. In this report, we present evidence contrary to this hypothesis, and show the importance of locomotor experience for emotional development. Four studies bearing on this conclusion have shown that (1) when age is held constant, locomotor experience accounts for wariness of heights; (2) “artificial” experience locomoting in a walker generates evidence of wariness of heights; (3) an orthopedically handicapped infant tested longitudinally did not show wariness of heights so long as he had no locomotor experience; and (4) regardless of the age when infants begin to crawl, it is the duration of locomotor experience and not age that predicts avoidance of heights. These findings suggest that when infants begin to crawl, experiences generated by locomotion make possible the development of wariness of heights.

The development of infant sensitivity to biomechanical motions.

3 experiments were conducted to examine infant sensitivity at 20, 30, and 36 weeks of age to the 3-dimensional structure of a human form specified through biomechanical motions. All 3 experiments manipulated occlusion information in computer-generated arrays of point-lights moving as if attached to the major joints and head of a person walking. These displays are readily recognized as persons by adults when occlusion information is present, but not when it is absent or inconsistent with the implicit structure of the human body. Converging findings from Experiments 1 and 2 suggested that 36-week-old infants were sensitive to the presence of occlusion information in point-light walker displays; neither 20- nor 30-week-old infants showed any sensitivity to this information. The results of Experiment 3 revealed further that 36-week-old infants were sensitive to whether or not the pattern of occlusion was consistent with the implicit form of the human body, but only when the displays were presented in an upright orientation. These findings are interpreted as suggesting that infants, by 36 weeks of age, are extracting fundamental properties necessary for interpreting a point-light display as a person.

The partial-lag design: A method for controlling spontaneous regression in the infant-control habituation paradigm*

The problem of spontaneous regression in the infant control procedure is discussed and empirical evidence demonstrating that it contributes significantly to postcriterion looking scores is presented. Previous approaches to controlling spontaneous regression are reviewed and are found unsatisfactory and/or inefficient. A new approach utilizing a partial-lag design is presented as an alternative. In contrast to previous approaches, this method successfully controls spontaneous regression without requiring a group of babies exclusively for control purposes.

Automatic imitation of biomechanically possible and impossible actions: Effects of priming movements versus goals.

Recent behavioral, neuroimaging, and neurophysiological research suggests a common representational code mediating the observation and execution of actions; yet, the nature of this representational code is not well understood. The authors address this question by investigating (a) whether this observation-execution matching system (or mirror system) codes both the constituent movements of an action as well as its goal and (b) how such sensitivity is influenced by top-down effects of instructions. The authors tested the automatic imitation of observed finger actions while manipulating whether the movements were biomechanically possible or impossible, but holding the goal constant. When no mention was made of this difference (Experiment 1), comparable automatic imitation was elicited from possible and impossible actions, suggesting that the actions had been coded at the level of the goal. When attention was drawn to this difference (Experiment 2), however, only possible movements elicited automatic imitation. This sensitivity was specific to imitation, not affecting spatial stimulus-response compatibility (Experiment 3). These results suggest that automatic imitation is modulated by top-down influences, coding actions in terms of both movements and goals depending on the focus of attention.