Joseph M. Notterman

Visual Velocity Discrimination: Effects of Spatial and Temporal Cues

Weber ratios were obtained for visual velocity discrimination under three topographic conditions with the same subjects and psychophysical procedures. The conditions differed regarding the presence of either temporal or spatial cues, these being correlated in magnitude with stimulus velocity. Systematic effects of the cues upon the level of velocity discrimination were noted.

Demonstration of the Influence of Stimulus and Response Categories upon Difference Limens

Representative types of stimulus and response categories were used with the same subjects in determining the difference threshold for visual velocity discrimination. The observed interaction between these variables and difference limens was pronounced.

Variables influencing outflow–inflow interpretations of tracking performance: Predictability of target motion, transfer function, and practice.

Experimental evidence can be found in support of either outflow or inflow theories of voluntary action. Accordingly, the empirical problem becomes one of ascertaining fundamental conditions under which the dichotomy plainly manifests itself. Using a within-subjects design, six undergraduates were given pursuit tracking training. The independent variables were (a) presence or absence of regularity (predictability) in the back-and-forth motion of the target, (b) type of control stick (with attendant proprioceptive feedback) used to drive the cursor, and (c) practice. The dependent variable was the time integral of error. The following results were significant (p less than .05, two-tailed): (a) A pressure stick is better than a freely moving one when tracking a random target; this finding supports a reactive force inflow model. The converse is true for a predictable target and is therefore supportive of an outflow interpretation. (b) Regardless of kind of target motion, an unloaded stick is better than an elastically loaded one at the beginning of training (outflow support) but worse by the end of training (inflow support). It is concluded that the motor outflow versus motor inflow dispute is amenable to parametric resolution.

Force differentiation in human subjects

Force of response was differentiated in four human Ss using a quantitative visual feedback procedure. Variations in the force required produced systematic changes in rate of response and in the precision with which the response was made.

Perception of Changes in Certain Exteroceptive Stimuli

Although cybernetic models of one sort or another have become quite common in behavioral research, and although these models theoretically require a capacity for system detection of changes in error, no general psychophysical description of the individual human beings ability to discriminate different rates of stimulation is available. An initial survey of this type has been attempted and is reported here. For reasons which appear to be related to the biological mechanisms underlying sensory information processing, it is concluded, first, that ancillary cues of rate-related final magnitude are more valuable than cues of stimulus duration; second, that direct attention to on-going change is less precise than attention to final values only; and third, that differences in isochronal stimulus rates occurring in place or extent are more readily perceived than differences in isochronal rate of change in energy content, at least for the stimuli and ranges examined.

INDIVIDUAL DIFFERENCES IN ABILITY TO USE EMG-DERIVED FEEDBACK

Evidence shows statistically reliable individual differences among unimpaired subjects in ability to use visual representation of electromyographic voltages. The visual information was displayed as a cursor in a tracking situation. The cursor was then blanked, with subjects being required to place the now invisible cursor over a target. Test-retest correlational significance is demonstrated. The rationale for using visual guidance in rehabilitating stroke victims suffering from loss in motor feedback receives support.

Visual-motor organization: differences between and within individuals

The research described in this monograph uses control theorys pursuit-tracking paradigm of voluntary movement to identify several elementary psychomotor tasks. They are simple to administer and tap increasingly complex, nonverbal cognitive or perceptual attributes. Two series of experiments are reported. Study 1 examined the hypothesis that dissimilar arrays of individual differences, as determined through test-retest correlations, may exist among the same subjects: first, across various static and dynamic visual and motor “tasks” selected from the terms of control theorys tracking equations and, second, in the organization of these tasks as represented by pursuit tracking. The hypothesis could not be rejected. Study 2 determined that test-retest individual differences in visual-motor organization not only persisted in the absence of practice, but that they also withstood active intervention by practice. This study also showed that subjects differ reliably in their ability to plan, i.e., to take advantage of coherence in visual-motor information.

Reinforcement rate and force proportional reinforcement

Abstract The research examines the consequences of making two reinforcement contingencies simultaneously available for the same bar-pressing response. Specifically, two experiments are described which concern the effects of reinforcement rate upon force proportional reinforcement (FPR). In Experiment 1, reinforcement rate was constrained by combining differential reinforcement of low rate with a force-proportional reinforcement contingency. The group of rats exposed to this regimen eventually showed a significant increase in response force compared to control groups. Experimental vs control response rates were not significantly different. In Experiment 2, reinforcement rate was affected through the expedient of relating the probability of obtaining a single pellet to the response force. The group for which the probability-force relationship was discontinuous came to exert higher forces than either a group for which the relationship was fairly continuous or an ordinary variable ratio control group. Response rate was significantly higher for the control group.

Effort expenditure during proportionally reinforced responding

A bar-pressing experiment was carried out in which laboratory rats were reinforced approximately in direct proportion to the level of time integral of force (“effort”) exerted per response. Over the course of training, the subjects increased in efficiency, as measured by amount of food obtained per unit effort exerted. It was not demonstrated, however, that the animals learned to take advantage of the effort-proportional reinforcement contingency.

An observed short-term motor memory effect for isometric force emission

Contrary to an earlier study, the accuracy of isometric force production is shown to fall under the influence of short-term motor memory, and in a manner quite similar to that previously observed for linear and rotary movement. Four paid male high school seniors pulled on a control stick with one of four designated target force bands. The target ranges were randomly varied in one phase of the experiment, and were the same for a series of consecutive responses in another. A red light came on after each response, and remained on for one of four durations; subjects were instructed not to respond while the light was on. Key variables accounting for the positive findings in the present experiment appear to be the availability of repetition (or massing), and the utilization of appropriate concurrent motor cues which are not supported by correlated visual cues.