Jeannine Pinto

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

Designing documentation to compensate for delocalized plans

Conceptual representation methods play a significant role in facilitating the software process. Recent studies explore and clarify the use of these representations and their impact on progress.

The visual perception of human locomotion.

To function adeptly within our environment, we must perceive and interpret the movements of others. What mechanisms underlie our exquisite visual sensitivity to human m ovement? To address this question, a set of psychophysical studies was conducted to ascertain the temporal characteristics of the visual perception of human locomotion. Subjects viewed a computer-generated point-light walker presented within a mask under conditions of apparent motion. The temporal delay between the display frames as well as the motion characteristics of the mask were varied. With sufficiently long trial durations, performance in a direction discrimination task remained fairly constant across inter-stimulus interval (ISI) when the walker was presented within a random motion mask but increased with ISI when the mask motion duplicated the motion of the walker. This pattern of results suggests that both low-level and high-level visual analyses are involved in the visual perception of human locomotion. These findings are discussed in relation to recent neurophysiological data suggesting that the visual perception of human movement may involve a functional linkage between the visual and motor systems.

Subconfigurations of the human form in the perception of biological motion displays.

We report four experiments examining processes that contribute to the perception of point-light displays of human locomotion. In three experiments, we employed a simultaneous masking paradigm to examine the visual systems use of configural information in global analyses of biological motion displays. In the fourth experiment, we obtained descriptions of our stimulus displays from naive observers. Performance in both the detection and identification studies suggests that the visual system responded equivalently to figures exhibiting any organization of limbs that is consistent with the human form. Moreover, the subconfigurations best detected were also most likely to be described independently as depicting a human figure. Thus our findings provide evidence that the visual system can exploit characteristic subconfigurations of the human form in the perception of human locomotion.

Mental models and software maintenance

Abstract Understanding how a program is constructed and how it functions are significant components of the task of maintaining or enhancing a computer program. We have analyzed vidoetaped protocols of experienced programmers as they enhanced a personnel data base program. Our analysis suggests that there are two strategies for program understanding, the systematic strategy and the as-needed strategy. The programmer using the systematic strategy traces data flow through the program in order to understand global program behavior. The programmer using the as-needed strategy focuses on local program behavior in order to localize study of the program. Our empirical data show that there is a strong relationship between using a systematic approach to acquire knowledge about the program and modifying the program successfully. Programmers who used the systematic approach to study the program constructed successful modifications; programmers who used the as-needed approach failed to construct successful modifications. Programmers who used the systematic strategy gathered knowledge about the causal interactions of the programs functional components . Programmers who used the as-needed strategy did not gather such causal knowledge and therefore failed to detect interactions among components of the program.

Experience, Context, and the Visual Perception of Human Movement.

Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement.

The visual perception of human and animal motion in point-light displays

Abstract Mounting neurophysiological evidence indicates that the visual analysis of human movement differs from the visual analysis of other categories of complex movement. If different patterns of neural activity underlie visual percepts of human and nonhuman movement, then psychophysical measures should elucidate different patterns of visual sensitivity to human movement and similarly complex, but nonhuman movement. To test this prediction, two psychophysical studies compared visual sensitivity to human and animal motions. Using a simultaneous masking paradigm, observers performed a coherent motion detection task with point-light displays of human and horse gait, presented upright and inverted. While task performance indicated the use of configural processing during the detection of both human and horse motion, observers demonstrated greater visual sensitivity to coherent human motion than coherent horse motion. Recent experience influenced orientation dependence for both types of motion. Together with previous neurophysiological findings, these psychophysical results suggest that the visual perception of human movement is both distinct from and shares commonalities with the visual perception of similarly complex, nonhuman movement.

The Knowledge Required for Tutorial Planning: An Empirical Analysis

Abstract A significant portion of tutorial interactions revolve around the bugs a student makes. When a tutor performs an intervention to help a student fix a programming bug, the problem of deciding how to help the student appears to require extensive planning. In this article, we identify five considerations tutors appear to take into account when they plan tutorial interventions for students’ bugs. Using data collected from human tutors working in the domain of introductory computer programming, we (1) identify the knowledge tutors use when they reason about the five planning considerations, and (2) show that tutors are consistent in the ways that they use the kinds of knowledge to reason about students’ bugs.

Providing the requisite knowledge via software documentation

Software documentation should be useful to the programmer trying to understand a program. The key in that sentence was the word should: by and large documentation has a very bad reputation. We have been working on trying to improve documentation, in order that it may realize its potential. In this case study, we examine a programmers use of documentation constructed along some specific guidelines. These guidelines, developed from our previous studies of documentation, are intended to help programmers draw causal connections between non-contiguous portions of programming plans in the program. This documentation appears to be helpful to a particular class of programmers, i.e., those who come to a program without the requisite background knowledge.