An improved technique for monitoring fixation in tachistoscopic tasks

A monocular lens mounted behind a stimulus screen was used to monitor fixation in a tachistoscopic recognition task. This technique was found superior to the often used “sideview technique” and as accurate as the method involving identification of a fixation stimulus. It was found that the “telescope technique” is preferable in those studies where presentation of a fixation stimulus might interfere with recognition or report of the experimental stimulus.     

A measurement technique for stability as applied in rifle shooting

A technique is described for the measurement, in the field, of stability and steadiness. Apparatus and method are provided along with suggested scoring procedures.     

An improved technique for creating hemifacial chimeras

In numerous studies, facial composites of the right and left hemifaces have been used to explore lateral differences in facial expressions. In the majority of these studies, a single technique has been used to create the stimuli: “Wolff’s split half technique,” which was devised at the beginning of the century. Chimeras thus made are weakened by several confounding factors (e.g., hair form, background, shadows), which are unrelated to the original stimuli and consequently may interfere with the examination of subtle facial expressions. This paper offers a modified method using computer graphics that seems to solve such drawbacks.     

Quiet eye duration,expertise, and task complexity in near and far aiming tasks

. Skilled (n = 12) and less skilled (n = 12) billiards players participated in 2 experiments in which the relationship between quiet eye duration, expertise, and task complexity was examined in a near and a far aiming task. Quiet eye was defined as the final fixation on the target prior to the initiation of movement. In Experiment 1, skilled performers exhibited longer fixations on the target (quiet eye) during the preparation phase of the action than their less skilled counterparts did. Quiet eye duration increased as a function of shot difficulty and was proportionally longer on successful than on unsuccessful shots for both groups of participants. In Experiment 2, participants executed shots under 3 different time-constrained conditions in which quiet eye periods were experimentally manipulated. Shorter quiet eye periods resulted in poorer performance, irrespective of participant skill level. The authors argue that quiet eye duration represents a critical period for movement programming in the aiming response.     

Multifractality in postural sway supports quiet eye training in aiming tasks: A study of golf putting

The ‘quiet eye’ (QE) approach to visually-guided aiming behavior invests fully in perceptual information's potential to organize coordinated action. Sports psychologists refer to QE as the stillness of the eyes during aiming tasks and increasingly into self- and externally-paced tasks. Amidst the ‘noisy’ fluctuations of the athlete's body, quiet eyes might leave fewer saccadic interruptions to the coupling between postural sway and optic flow. Postural sway exhibits fluctuations whose multifractal structure serves as a robust predictor of visual and haptic perceptual responses. Postural sway generates optic flow centered on an individual's eye height. We predicted that perturbing the eye height by attaching wooden blocks below the feet would perturb the putting more so in QE-trained participants than participants trained technically. We also predicted that QE's efficacy and responses to perturbation would depend on multifractality in postural sway. Specifically, we predicted that less multifractality would predict more adaptive responses to the perturbation and higher putting accuracy. Results showed that lower multifractality led to more accurate putts, and the perturbation of eye height led to less accurate putts, particularly for QE-trained participants. Models of radial error (i.e., the distance between the ball's final position and the hole) indicated that lower estimates of multifractality due to nonlinearity coincided with a more adaptive response to the perturbation. These results suggest that reduced multifractality may act in a context-sensitive manner to restrain motoric degrees of freedom to achieve the task goal.     

The error power spectrum as a technique for assessing the performance of the human operator in a simple task

The measurement of performance of a human operator in a closed loop control system is considered; it is suggested that the power spectrum of the fluctuations of his tracking error (or error spectral density curve) gives a useful picture of performance and the equipment and technique for producing such a curve is described briefly.

As an example of the technique the power spectra obtained on several subjects performing a simple task with a pressure joystick are given and the implications of the shape of the curve are discussed.     

Intermittency in human manual tracking tasks

We confirm Craik's (1947) observation that the human manual1y tracking a visual target behaves like an intermittent servo-control1er. Such tracking responses are indicative of "sampled" negative-feedback control but could be the result of other, continuous, mechanisms. Tracking performance therefore was recorded in a task in which visual feedback of the position of the hand-held joystick could be eliminated. Depriving the subjects of visual feedback led to smoother tracking and greatly reduced the signal power of their responses between 0.5-1.8 Hz. Their responses remained intermittent when they used feedback of their own position but not of the target to track a remembered (virtual) target. Hence, intermittency in tracking behavior is not exclusively a signature of visual feedback control but also may be a sign of feedback to memorized waveforms. Craik's (1947) suggestion that the intermittency is due to a refractory period following each movement was also tested. The errors measured at the start of each intermittent response, during tracking of slow waveforms, showed evidence of a small error deadzone (measuring 0.7 cm on the VDU screen or 0.80 degrees at the eye). At higher target speeds, however, the mean size of starting errors increased, and the upper boundary of the distribution of starting error was close to that expected of a refractory delay of approximately 170 ms between responses. We consider a model of the control system that can fit these results by incorporating an error deadzone within a feedback control loop. We therefore propose that the initiation of intermittent tracking responses may be limited by a positional error deadzone and that evidence for a refractory period between successive corrective movements can be satisfied without evoking an explicit timing or sampling mechanism.     

An improved method for tetrachoricr

From the ratio of the cross-products of a fourfold table, with the application of two tabled corrections, tetrachoricr's can be estimated with a mean discrepancy of less than .005 even when splits vary greatly from the medians. The necessary calculations can be handled by slide rule and the correction tables used without interpolation.     

An automated identification system for use with computer-controlled tasks

Monkeys of various species can use a joystick to perform a variety of computer-generated tasks. The purpose of this paper is to describe an automated system that determines which subject in a social group has completed a task. The system is based on a microchip that is easily injected into the forearm. The present paper demonstrates the technique with 1 animal that had a different chip in each arm.     

A technique for the measurement of aggressive behavior in mice

This paper describes an apparatus permitting the study of aggressive behavior in mice. Aggressive behavior may be spontaneous or induced by means of an electric shock delivered through the tail.     

Generalized multivariate lens model analysis for complex human inference tasks

A generalized multivariate lens model is presented which will permit the analysis of complex human inference tasks. Such tasks, occurring in their natural ecology, may involve judgments or decisions on multiple criteria and/ or where the influence of theoretically interesting partitions or augmentations of cue profiles needs to be systematically delineated. The generalized model incorporates the standard, hierarchical, and fully partialed lens models, the initial elaborations of which were made by N. J. Castellan (1972, Organizational Behavior and Human Performance, 8, 242–261) and T. R. Stewart (1976, Psychometrika, 41, 101–120). Both multivariate and univariate lens model equations are presented within a common notational system. An example which demonstrates some aspects of the generalized model is discussed in detail. Other potential applications for the model are outlined.     

An analysis of motor coordination components for various localization tasks

Localization abilities of subjects in three perceptual-motor tasks were considered before and after an exposure to a visual distortion. During this distortion the subject observed his hand ballistically point to an invisible but audible target while either receiving or not receiving knowledge of results (KR) concerning pointing accuracy. Also, subjects either received a 1- or a 4-sec rest period between each of 30 exposure ballistic pointing actions. The pre- and postexposure tasks involved the ability of a subject to accurately point to an occluded and stationary auditory target, to point to the straight-ahead position in space, and to indicate when a moving, auditory target was perceived as being in the straight-ahead position. For these tasks, the pre- vs. postexposure localization difference scores are referred to as the negative aftereffect, the proprioceptive shift, and the auditory shift, respectively. Wilkinson's (1971) two-component additive model (negative aftereffect = proprioceptive shift plus auditory shift) held when KR was given regardless of amount of rest between exposure pointing responses. With a 4-sec rest and no KR, the relationship between coordination components was nonadditive (negative aftereffect greater than proprioceptive shift plus auditory shift).     

Estimating the difference limen in 2AFC tasks: Pitfalls and improved estimators

Discrimination performance is often assessed by measuring the difference limen (DL; or just noticeable difference) in a two-alternative forced choice (2AFC) task. Here, we show that the DL estimated from 2AFC percentage-correct data is likely to systematically under- or overestimate true discrimination performance if order effects are present. We show how pitfalls with the 2AFC task may be avoided and suggest a novel approach for analyzing 2AFC data.     

An improved respiratory system for curarized rats

A respiratory system is described in which peak expired CO₂ is continuously monitored from curarized rats. Another alteration from previous systems is that an endotracheal tube is used to minimize dead air space. The adequacy of the system was tested by maintaining curarized rats at one level of peak expired CO₂ for varying periods of time and by keeping rats at different peak expired CO₂ levels for a fixed period of time. Results of blood gas analyses indicated that values obtained with this system are similar to values in noncurarized rats, and that manipulation of expired CO₂ is an effective means of altering blood gas values.     

An improved video multiplexer for behavioral research

Wellens and Revert (1979) described a solid-state circuit that allowed two sources of video information to be multiplexed and recorded using one videotape machine. On playback, the demultiplexed video signal allowed the original video channels to be viewed independently on separate television monitors. Recent changes in videocassette recorder technology have improved the playback quality of recorded images but disrupt the demultiplexing process when freeze frame or search options are selected. Improved multiplexing techniques that overcome these limitations are described.