Two Routes to Expertise in Mental Rotation

The ability to imagine objects undergoing rotation (mental rotation) improves markedly with practice, but an explanation of this plasticity remains controversial. Some researchers propose that practice speeds up the rate of a general‐purpose rotation algorithm. Others maintain that performance improvements arise through the adoption of a new cognitive strategy—repeated exposure leads to rapid retrieval from memory of the required response to familiar mental rotation stimuli. In two experiments we provide support for an integrated explanation of practice effects in mental rotation by combining behavioral and EEG measures in a way that provides more rigorous inference than is available from either measure alone. Before practice, participants displayed two well‐established signatures of mental rotation: Both response time and EEG negativity increased linearly with rotation angle. After extensive practice with a small set of stimuli, both signatures of mental rotation had all but disappeared. In contrast, after the same amount of practice with a much larger set both signatures remained, even though performance improved markedly. Taken together, these results constitute a reversed association, which cannot arise from variation in a single cause, and so they provide compelling evidence for the existence of two routes to expertise in mental rotation. We also found novel evidence that practice with the large but not the small stimulus set increased the magnitude of an early visual evoked potential, suggesting increased rotation speed is enabled by improved efficiency in extracting three‐dimensional information from two‐dimensional stimuli.     

Perceiving object motion using vision and touch

In a previous experiment, we showed that bistable visual object motion was partially disambiguated by tactile input. Here, we investigated this effect further by employing a more potent visuotactile stimulus. Monocular viewing of a tangible wire-frame sphere (TS) rotating about its vertical axis produced bistable alternations of direction. Touching the TS biased simultaneous and subsequent visual perception of motion. Both of these biases were in the direction of the tactile stimulation and, therefore, constituted facilitation or priming, as opposed to interference or adaptation. Although touching the TS biased visual perception, tactile stimulation was not able to override the ambiguous visual percept. This led to periods of sensory conflict, during which visual and tactile motion percepts were incongruent. Visual and tactile inputs can sometimes be fused to form a coherent percept of object motion but, when they are in extreme conflict, can also remain independent.     

THE INFORMATIONAL BASIS OF MOTION COHERENCE

Abstract— Observers judged the motion coherence of random-dot cinematograms. Theoretical models were developed for coherence matches between cinematograms constructed from different angle distributions. Evidence is presented that coherence matches are made on the basis of the Shannon-Wiener information entropy. We show how the formal structure of information theory may be used to predict perceived pattern goodness when the underlying distributions of pattern alternatives are implicit in the judgment task.     

MacPsych: An electronic discussion list and archive for psychology concerning the Macintosh computer

MacPsych is an electronic mail discussion list and an electronic archive for those using the Macintosh in psychology. The discussion list allows psychologists from around the world to ask questions and discuss issues relating to the use of the Macintosh in psychology. The archive is a place where list members may share software and other files of relevance. The Society for Computers in Psychology sponsors the discussion list, and the journalBehavior Research Methods, Instruments, & Computers has designated the archive as the distribution site for Macintosh software and files described in its pages. Those interested may join the list by sending electronic mail to macpsych-request@stolaf.edu. The archive can be accessed via anonymous ftp at ftp.stolaf.edu in the directory pub/macpsych.     

The suppression of exciting thoughts

We examined how the suppression of an exciting thought influences sympathetic arousal as indexed by skin conductance level (SCL). Subjects were asked to think aloud as they followed instructions to think about or not to think about various topics. Experiment 1 showed that trying not to think about sex, like thinking about sex, elevates SCL in comparison to thinking about or not thinking about less exciting topics (e.g., dancing). Experiment 2 revealed that the suppression of the thought of sex yielded SCL elevation whether or not subjects believed their think-aloud reports would be private or public, and it also revealed that the effect dissipated over the course of a few minutes. Experiment 3 found such dissipation again but showed that subsequent intrusions of the suppressed exciting thought are associated with further elevations in SCL over 30 min. Because such an association was not found when subjects were trying to think about the exciting thought, it was suggested that the suppression of exciting thoughts might be involved in the production of chronic emotional responses such as phobias and obsessive preoccupations.     

Preattentive vision and perceptual groups

Recent evidence suggests that preattentive processing may not be limited to the analysis of simple stimulus features as previously suggested. To explore this idea a visual search task was used to test whether the shapes of several perceptual groups can be processed in parallel. Textured displays that give rise to strong perceptual grouping were used to create figures on a background. Search times for a target figure distinguished by a unique shape were found to be independent of the number of distractor figures in the display. This result indicates that perceptual groups may be processed in parallel and suggests an expanded role for preattentive processing in vision.     

Interocular transfer of visual aftereffects

A number of the well-known visual after-effects of adaptation exhibit interocular transfer, so that presentation of an adaptation figure to one eye produces a temporary change in the performance of the nonadapted eye. This outcome is usually attributed to the involvement of binocular visual neurons that respond to stimulation of either eye. The fact that interocular transfer is incomplete (i.e., the transferred aftereffect is smaller in magnitude than that induced and measured in the same eye) is routinely cited as evidence for the involvement of monocular neurons. This article critically examines these two interpretations, which are developed in terms of a neural model of interocular transfer. No evidence, logical or empirical, was obtained for rejecting the model. Our analysis further shows that the model must assume some type of pooling process that operates over all tested neurons, both adapted and unadapted. Finally, general implications of the interocular transfer model are discussed, the aim being to delimit the conclusions that may be drawn from interocular transfer experiments.     

Tachistoscopic perception under head tilt

Subjects attempted to identify singly presented letters, flashed briefly at six different locations equidistant from fixation. The locations were at 1, 3, 5, 7, 9, and 11 o’clock on an imaginary circle. The subjects performed both with their heads upright or tilted 60° (i.e., through 2 and 8 o’clock or through 10 and 4 o’clock). In Experiment 1, the letters were projected in a gravitationally fixed rectangular surround, and accuracy of report depended largely on the locations of the letters in gravitational coordinates, although there was clear evidence of a retinal influence as well. In Experiment 2, the surround was circular and accuracy depended principally on retinal location, although there was also a gravitational influence. Analysis of individual data suggested that, when their heads were tilted, subjects generally adopted a reference frame which lay between the retinal and gravitational frames, closer to one than the other but typically coinciding with neither. We conclude that the subjective reference frame does not depend on a poststimulus correction, but rather that stimulus information is incorporated directly into the subjective frame. The data also suggested that lateral asymmetries depend on a perceptual rather than a retinal interpretation of left and right visual fields.