How do somersaulters land on their feet?

Body movements of trampolinists landing upright from forward somersaults, with eyes open and closed, were analyzed to test a theory of how braking and timing of actions are conjointly controlled. In regulating landing, rotation has to be slowed by extending the body so that it reaches the upright just as the feet hit the trampoline. Extending a theory of visual control of linear braking, it was hypothesized that upright landing is achieved by perceptually regulating body extension so as to keep the ratio angle of body to upright: rate of change of angle (the tau function of the angle) proportional to time-to-landing. The data support the hypothesis, indicate that vision improves precision of control, and argue further for the value of the tau function in the perceptual regulation of action.     

Information for step length adjustment in running

The purpose of this study was to directly test the hypothesis that the tau parameter, as introduced by Lee et al. [Lee, D. N., Lishman, J. R., & Thomson, J. A. (1982). Regulation of gait in long jumping. Journal of Experimental Psychology: Human Perception and Performance, 8, 448-459] and Warren et al. [Warren, W. H., Young, D. S., & Lee, D. N. (1986). Visual control of step length during running over irregular terrain. Journal of Experimental Psychology: Human Perception and Performance, 12, 259-266], is the primary information used to regulate step length in running toward a ground target. Visual information available to research participants performing a facsimile of a long jump approach run was manipulated, and the effects on task performance and running gait were observed. Task performance and running gait were unaffected or minimally affected by (a) a perturbation of the normal optical expansion of the target, (b) elimination of global optical flow - including the focus of expansion, and (c) elimination or severe degradation of visual information about distance from the target as well as running velocity. The findings are inconsistent with notions that time-to-arrival with a ground target while running is predominantly specified optically by (a) local tau, (b) global tau, or (c) a distance/velocity computational strategy. A multisensory tau hypothesis regarding informational support for step length adjustment in running is offered.     

Guiding Movement by Coupling Taus

Studies of sensory guidance of movement in animals show that large nervous systems are not necessary for accurate control, suggesting that guidance may be based on some simple principles. In search for those principles, a theory of guidance of movement is described, which has its roots in Gibson's pathfinding work on visual control of locomotion (J. J. Gibson, 1958/this issue). The theory is based on the use of the simple but powerful variable tau, the time-to-closure of a gap at the current gap closure rate (whatever the gap's dimension—distance, angle, force, etc.); and on the principle of tau-coupling (keeping two Ts in constant ratio). In this article, I show how tau-coupling could be used to synchronize movements and regulate their kinematics. Supportive experimental results are reported. I also show theoretically how sensory-taus, defined on sensory input arrays, can specify motion-taus through tau-coupling; how the braking procedure of keeping tau.dot stable is a particular case of tau.coupling; and how tools for steering (e.g., limbs, whole bodies, cars, or aircraft) could be built from tau-couplings, which would enable steering control in a variety of situations, including steering straight and curved courses to goals, steering and controlling speed at the same time, steering around obstacles, and asymptoting on surfaces as when landing. Some movements also involve intrinsic guidance from within, and a hypothesis on intrinsic guidance by tau is introduced, supported by experiments spanning different activities.     

Global and local contributions to the optical specification of time to contact: observer sensitivity to composite tau

First-order time remaining until a moving observer will pass an environmental element is optically specified in two different ways. The specification provided by global tau (based on the pattern of change of angular bearing) requires that the element is stationary and that the direction of motion is accurately detected, whereas the specification provided by composite tau (based on the patterns of change of optical size and optical distance) does not require either of these. We obtained converging evidence for our hypothesis that observers are sensitive to composite tau in four experiments involving relative judgments of time to passage with forced-choice methodology. Discrimination performance was enhanced in the presence of a local expansion component, while being unaffected when the detection of the direction of heading was impaired. Observers relied on the information carried in composite tau rather than on the information carried in its constituent components. Finally, performance was similar under conditions of observer motion and conditions of object motion. Because composite tau specifies first-order time remaining for a large number of situations, the different ways in which it may be detected are discussed.     

Anxiety Influences the Perceptual-Motor Calibration of Visually Guided Braking to Avoid Collisions

We investigated whether anxiety influences perceptual-motor calibration in a braking to avoid a collision task. Participants performed either a discrete braking task (Experiment 1) or a continuous braking task (Experiment 2), with the goal of stopping before colliding with a stop sign. Half of participants performed the braking task after an anxiety induction. We investigated whether anxiety reduced the frequency of crashing and if it influenced the calibration of perception (visual information) and action (brake pressure) dynamically between-trials in Experiment 1 and within-trials in Experiment 2. In the discrete braking task, anxious participants crashed less often and made larger corrective adjustments trial-to-trial after crashing, suggesting that the influence of anxiety on behavior did not occur uniformly, but rather dynamically with anxiety amplifying the reaction to previous crashes. However, when performing continuous braking, anxious participants crashed more often, and their within-trial adjustments of deceleration were less related to visual information compared to controls. Taken together, these findings suggest that the timescale and nature of the task mediates the influence of anxiety on the performance of goal-directed actions.     

On the link between mind wandering and task performance over time

Here we test the hypothesis that fluctuations in subjective reports of mind wandering over time-on-task are associated with fluctuations in performance over time-on-task. In Study 1, we employed a singleton search task and found that performance did not differ prior to on- and off-task reports, nor did individual differences in mind wandering predict differences in performance (so-called standard analytic methods). Importantly however, we find that fluctuations in mind wandering over time are strongly associated with fluctuations in behavior. In Study 2, we provide a replication of the relation between mind wandering and performance over time found in Study 1, using a Flanker interference task. These data indicate (1) a tight coupling between mind wandering and performance over time and (2) that a temporal-analytic approach can reveal effects of mind wandering on performance in tasks where standard analyses fail to do so. The theoretical and methodological implications of these findings are discussed.     

A perception-action strategy for hummingbirds

Many human and animal tasks are thought to be controlled with the tau informational variable. It is widely accepted that controlling the rate of change of tau (tau) during decelerative tasks, such as when braking or landing, is one common perceptual control strategy. However, many tasks require accelerating before decelerating to a goal, such as reaching. An advancement of tau theory shows how a single action formula may be used to control the full action unit from initiation to peak velocity, and to rest at the goal, with the same perceptual tau information as before and accounting for the same decelerative kinematics as before. Here, we test the theory against data from high-speed video of a hummingbird flying to its flower feeder. We find that the theory accounts for 97% of the variance in the data, and thus supports it.     

Evidence of difficulties in sustained attention in children with ADDH

It has been suggested that children with ADDH have specific difficulties in sustained attention. Despite some early studies supporting this position, many recent reports using continuous peformance tests (CPTs) have failed to confirm this hypothesis. Possible reasons for this discrepancy are outlined and an attempt to corroborate and extend an earlier study (Sykes, Douglas, & Morgenstern, 1973) was undertaken. CPT results in normal children indicated that changes in performance over time, although not affected by gender, were influenced by age. Data from ADDH subjects indicated that they performed significantly more poorly with time on task than did controls. These results suggest that the ability to sustain attention increases with age and does not vary by gender. Furthermore, difficultues in the ability to sustain attention can be demonstrated in children with ADDH. Finally, it is suggested that within-age-level comparisons between groups of ADDH and controls would be more clinically sensitive than across-age-group comparisons.This research was supported in part by a Sara Spencer Research Fellowship granted to the first author. Portions of this research were presented at the 17th annual meeting of the International Neuropsychological Society, Vancouver.     

A test of the tau-dot hypothesis of braking control in the real world

A controlled experiment used instrumented vehicles in a real-world driving task to compare D. N. Lee's (1976) tau-dot hypothesis of braking control with an alternative based on the direct estimation and control of ideal deceleration (T. Yates, M. Harris, & P. Rock, 2004). Drivers braked to stop as closely as possible to a visual target from different starting speeds and times-to-contact. The data provided little support for the tau-dot hypothesis, and analysis suggested that braking in the real world is better explained by a direct deceleration strategy.     

Second-order probability affects hypothesis confirmation

Bayesian confirmation measures give numerical expression to the impact of evidence E on a hypothesis H. All measures proposed to date are formal—that is, functions of the probabilities Pr(E∧H), Pr(E∧¬H), Pr(¬E∧H), Pr(¬E∧¬H), and nothing more. Experiments reported in Tentori, Crupi, and Osherson (2007) suggest that human confirmation judgment is not formal, but this earlier work leaves open the possibility that formality holds relative to a given semantic domain. The present study discredits even this weaker version of formality by demonstrating the role in confirmation judgments of a probability distribution defined over the possible values of Pr(E∧H), Pr(E∧¬H), Pr(¬E∧H), and Pr(¬E∧¬H)—that is, a second-order probability. Specifically, when for each of the latter quantities a pointwise value is fixed with a maximal second-order probability, evidence impact is rated in accordance with formal and normatively credible confirmation measures; otherwise evidence impact is systematically judged as more moderate.     

Driver responses to motorcycle and lead vehicle braking events: The effects of motorcycling experience and novice versus experienced drivers

In many countries, motorcyclists are over-represented in traffic collision fatalities and injuries compared to vehicle registrations. Why drivers may violate the right-of-way of motorcyclists traveling as lead vehicles in front of drivers is empirically examined in two studies that were conducted with a moderate-fidelity driving simulator. The purpose of the first study was to determine if drivers, who also held a motorcycle license (N = 16), drove cars differently than regular drivers (N = 16) around motorcycles. The two groups did not differ on responses to motorcycling braking events, which was consistent with previous research on car following. The second study compared the driving performance of sixteen novice teenage drivers (M = 16.2 years of age) to 15 experienced drivers (M = 32.9) over the span of six monthly simulator sessions. Novice drivers’ perception response times (PRT) to the braking events were significantly longer than those of the experienced drivers. PRTs to motorcycle and lead vehicle braking events decreased over sessions. For all participants, PRTs to the motorcycle events were longer than to the car events. The implications of these results for motorcyclists and drivers with different levels of experience are discussed.     

Predicting employee turnover from performance,satisfaction, and leader-member exchange

As part of a study of the role of supervision in, predicting turnover, 105 nurses provided confidential data on leader-member exchange and satisfaction with supervision, while their supervisors provided performance evaluation information. Although results reaffirmed an inverse correlation between employee performance and turnover (r=–.23p<.05), only directional support was obtained for the hypothesis that performance moderates the relationship between satisfaction with supervision and turnover. Turnover was also not found to be curvilinearly related to performance. Additionally, the, results did not replicate an earlier finding that leader-member exchange is a strong predictor of empolyee turnover. The results are interpreted as underscoring the difficulty of predicting turnover from affect, and the need to, develop refined theoretical models that specifically link these constructs.     

Distraction,attentional conflict,and drivelike behavior

Two studies provide evidence supporting a distraction-conflict view of social facilitation effects. Study 1 demonstrated that presence of an audience produced drivelike effects on the latency and vigor of a motor response. This effect, however, only occurred when attending to the audience caused attentional conflict. Study 2 demonstrated that in a two-task setting, attentional conflict, resulting from having to choose which task to work on, led to poorer performance on a complex copying task (p < .01, one tailed) and a larger percentage of dominant responses on J. L. Cohen and J. H. Davis' (Journal of Personality and Social Psychology, 1973, 27, 74–85) hidden word task (p < .04, one tailed), relative to a yoked control. Study 2 is consistent with earlier reports that choice heightens drivelike effects, while Study 1 indicates that attentional conflict contributes to social facilitation phenomena.     

Speed, size, and edge-rate information for the detection of collision events

In the present study an alternative analysis to tau was considered that was based on perceived speed and size and that assumed constant deceleration for the detection of collision events. Observers were presented with displays simulating a 3-D environment with obstacles in the path of observer motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. Observers had to detect which trials resulted in a collision. The results indicate that collision detection varied as a function of the size of the obstacles, observer speed, and edge rate--findings not predicted by an analysis of tau. The results suggest that observers use an analysis based on speed and size information. A model that assumes constant deceleration is proposed for braking control.     

A central performance drop with luminance stimuli requiring spatial integration

This study reports four experiments that analyzed detection performance for luminance contrasts as a function of retinal eccentricity in order to find further support and explanations for the central performance drop (CPD) in the fovea. In the first experiment, 10 participants (16-37 years of age) had to detect a target patch in a stimulus consisting of bright and dark pixels. Luminance differences between target and context areas were achieved by placing a different number of bright (and dark) pixels in the target and the context area. Results showed a marked CPD; that is, performance did not peak in the fovea but in the parafovea. A spatial integration hypothesis was proposed to explain this CPD. Alternative explanations were tested in three further experiments with a total of 28 participants from 19-46 years of age (using the decision criterion effect, the selective masking effect, and inhibition by high frequencies). The findings did not contradict the spatial-integration hypothesis.     

The Effects of Regulatory Focus on Braking Speed1

According to regulatory focus theory ( Higgins, 1997 ), promotion focus is concerned with accomplishments and aspirations leading to strategic eagerness; whereas prevention focus is concerned with safety and responsibilities leading to strategic vigilance. In this study, we investigate how regulatory focus theory can predict braking behavior in driving. In Study 1, participants' assessed regulatory focus strength as measured by chronic personality differences in regulatory focus predicted braking speed, in that chronic prevention‐oriented participants initiated braking earlier, as compared to promotion‐oriented people. In Study 2, we experimentally induced regulatory focus and showed that induced prevention focus enhanced braking speed (i.e., faster), as compared to induced promotion focus.     

Judgment of line orientation depends on gender, education, and type of error

Visuospatial tasks are particularly proficient at eliciting gender differences during neuropsychological performance. Here we tested the hypothesis that gender and education are related to different types of visuospatial errors on a task of line orientation that allowed the independent scoring of correct responses ("hits", or H) and one type of incorrect responses ("commission errors", or CE). We studied 343 volunteers of roughly comparable ages and with different levels of education. Education and gender were significantly associated with H scores, which were higher in men and in the groups with higher education. In contrast, the differences between men and women on CE depended on education. We concluded that (I) the ability to find the correct responses differs from the ability to avoid the wrong responses amidst an array of possible alternatives, and that (II) education interacts with gender to promote a stable performance on CE earlier in men than in women.     

Bimodal score distributions and the Myers-Briggs Type Indicator: fact or artifact?

We examined Myers-Briggs Type Indicator (MBTI) score distributions computed using item response theory (IRT) to assess the generalizability of earlier bimodality reports that have been cited in support of the "type" versus "trait" view of personality. Using the BILOG IRT program to score a sample of approximately 12,000 individuals who participated in leadership development programs, theta score distributions for the 4 dimensions of the MBTI computed using 10 (the BILOG default) versus 50 quadrature points were compared. Results indicated that past reports of bimodality were artifacts caused by BILOG's default use of a small number of quadrature points; when larger numbers of points were used, score distributions became strongly center-weighted. Although our findings are not supportive of the "type"-based hypothesis, the extremely high correlations between theta scores (rs > .996) suggest that no practical differences would be expected as a function of the number-of-quadrature-points decision.     

EEG asymmetry and sleep mentation during REM and NREM

The hypothesis that dreaming is mediated by the right hemisphere was evaluated by monitoring EEG power asymmetry during REM and NREM sleep, and obtaining mentation reports when short-term temporal shifts in the EEG indicated relative left- or right-hemispheric dominance. Content analyses provided no support for the right-hemisphere hypothesis; indeed, some scales showed higher content during relative left-hemispheric dominance. In contrast to earlier reports, no difference between REM and NREM in EEG asymmetry was observed.     

Performance reactivity in a continuous-performance task: Implications for understanding post-error behavior

Although there has been considerable interest in the effects of errors on subsequent performance, relatively few studies have considered the effects of non-error events that contain some performance-relevant information, such as correct performance on critical trials. In the present article, we propose and assess a hypothesis of performance reactivity. In support of this hypothesis, we provide evidence of performance decrements following both incorrect and correct responses but not following performance-irrelevant events. More specifically, in a continuous response task (Sustained Attention to Response Task), we (1) replicate previous findings that errors of commission on rare NOGO trials produce decrements in subsequent performance, and (2) observe that correct withholds to NOGO trials produce decrements in subsequent accuracy relative to task-irrelevant tones. These results corroborate a hypothesis that some error-related effects on subsequent performance are not unique, but are instead a particularly salient version of a more general performance-reactivity effect.