Some effects of noise on visual performance

A group of ten subjects showed impaired performance, when watch-keeping on a display made up of steam-pressure gauges, in 100 db. noise as compared with 70 db. On the easier task of watch-keeping on a display made up of small lights, another group of twenty subjects showed no overall effect of noise. Individual subjects who showed a practice effect on the latter task comparable to that shown by all subjects on the former one, however, also showed a similar effect of noise.

In addition, performance on the light-watching became relatively less efficient in noise with continued exposure: and although parts of the task were still adequately carried out, others were not. The fact that noise effects are thus functions of individual differences, of visibility of signal, and of length of performance in noise, allows us to explain the negative findings of many previous workers.     

Witnessed aggression: influence of an observer's sex and values on aggressive responding.

Two experiments investigated the effects of the presence of an observer on aggressive responding. In one experiment, male subjects observed by a male aggressed more than those observed by a female. When the male observer was removed from the situation, subjects' level of aggressiveness more closely matched the level manifested by the opponent. The removal of the female observer had little effect on the subjects' behavior. In the second experiment, the male or female observer of the subject's behavior was disguised as a member of an organization with explicit values (aggressive or pacifistic) regarding the use of aggression. In this case, significant differences in aggression were associated with the observer's values but not the observer's sex. Following the departure of the observer, the shock settings of subjects in the two aggressive-value observer groups showed a signifcant decrease. The average shock setting of subjects in the two pacifistic-value observer groups remained at about the same level. In sum, the results indicated that the subjects' aggressive behavior was apparently a function of their expectations of approval for such behavior, based on the inferred or explicit values of the observer. The results were further discussed in terms of social learning theory.     

Effect of an observer's presence on facial behavior during dyadic communication

In everyday life, people communicate not only with another person but also in front of other people. How do people behave during communication when observed by others? Effects of an observer (presence vs absence) and interpersonal relationship (friends vs strangers vs alone) on facial behavior were examined. Participants viewed film clips that elicited positive affect (film presentation) and discussed their impressions about the clips (conversation). Participants rated their subjective emotions and social motives. Durations of smiles, gazes, and utterances of each participant were coded. The presence of an observer did not affect facial behavior during the film presentation, but did affect gazes during conversation. Whereas the presence of an observer seemed to facilitate affiliation in pairs of strangers, communication between friends was exclusive and not affected by an observer.     

Some effects of progressively lowering electromyographic levels with feedback procedures on the frequency of stuttered verbal behaviors

Feedback procedures were used to progressively decrease the EMG activity of three stutterers during connected speech tasks. Single subject experimental designs were used which allowed for procedural changes as dictated by each subject's performance. All three subjects demonstrated clinically significant decreases in disfluencies and generalization of the treatment effects for an oral reading task, while one of the subjects also showed this effect for a conversational speech task. The subjects' strategies for manipulating the feedback tone seemed to be related to reduction in many of the motoric and prosodic complexities of speech which may have been importantly related to enhancing and maintaining fluency.     

Some relationships between adaptation and electromyographic activity at laryngeal and masseter sites in stutterers

Cumulative integrated electromyographic (EMG) activity was recorded from laryngeal and masseter sites from ten stutterers during a five trial oral adaptation sequence. Results showed more activity at the laryngeal site than the masseter site. While significant reductions in EMG activity were not found, patterns were shown to be related to the subjects' dysfluency patterns over trials. Results were interpreted as suggesting that reduced muscle activity and adaptation (when they occur) are artifacts of other behavioral modifications resulting from overt motor practice.     

Some effects of the conditioned suppression paradigm on operant discrimination performance

Three experiments were conducted with rats to determine the effects of electric shock on responding during an operant discrimination. In two of these experiments, a conditioned suppression procedure was superimposed upon a stimulus signalling the availability of food reinforcement (S(D)). Response rates were greatly suppressed, not only in the warning signal periods which preceded each shock, but in the presence of S(D), and the stimulus signalling the unavailability of reinforcement (S(Delta)) as well. A third experiment, in which a very mild shock was used without a warning signal, demonstrated an increased response rate in S(D) and S(Delta), although this effect was rather unsystematic. In a similar study, Hearst (1965) found an increased rate in S(Delta) independent of any change in the S(D) rate. The present study failed to obtain Hearst's effect but illustrated a suppressive effect with a similar procedure.     

Cardiac and electromyographic indices of attention: suggested situational adaptation effects.

Neck muscle action potentials and heart rate variability were recorded on 30 male hospital patients prior to and during performing on a short-lasting test of detecting auditory lateral shifts. A positive correlation (r = 0.49) was found during the second day but not during the first day of testing. The correlation is compatible with Obrist's somatic coupling hypothesis. Its absence during the first day suggests that subjects must adapt to the test situation before any reliable relations between physiological measures can be observed.     

Effects of skill practice on electromyographic activity patterns and frequency spectra

The purpose of this research was to investigate motor skill practice related changes in the activity pattern and mean frequency of the electromyogram and the subsequent motor performance. By using both electromyographic (EMG) activity levels and the frequency spectrum of the EMG signal, it is possible to gain an understanding of the modifications that may occur with skill acquisition. Subject's angular position and bipolar surface EMG activity from the biceps brachii and triceps brachii muscles were recorded and digitized at 1000 samples/second. Movement time and EMG data averaged over early and late practice trials were compared to evaluate the effects of practice on EMG activity patterns (RMS) and the EMG frequency spectra (mean frequency). Changes in EMG activity and frequency patterns observed at both movement velocities reflect modifications in the control of force gradation in relation to skill practice and learning. Although it is not possible to assess specific changes in motor unit recruitment order, it appears that motor units were controlled in a different manner after skill practice.     

The effects of a discriminative cue and an incompatible activity on generalized imitation

Four noncompliant retardates were observed in a generalized imitation study. Two variables were studied: provision of a competing reinforced activity, and use of a cue to aid discrimination between reinforced and nonreinforced imitations. Both variables were found to increase the rate of discrimination between the two sets of stimuli. Greatest discrimination occurred when both cue and alternative task were present. Discrimination decreased when the variables were removed. Results are interpreted as implying that imitation of nonreinforced cues in generalized imitation procedures varies with the degree to which reinforcement is available for other activity, as well as with the complexity of the discrimination problem. These results help indicate conditions under which the generalized imitation effect may be observed in more naturalistic settings.     

Emotional responding following experimental manipulation of facial electromyographic activity

Increases in zygomatic electromyographic (EMG) responding have been reported during the imagination of positive affective scenes, and increases in corrugator EMG have been reported during negative affective scenes. Thirty female subjects were instructed to imagine three positive affective scenes and three negative affective scenes. During the initial imagination of each scene, the subject was told simply to imagine the situation. The subject then imagined the situation again and was instructed to enhance the muscle tension in one of two muscle groups (the zygomatic muscles for positive scenes and the corrugator muscle for negative scenes). The subject then imagined the scence a third time and was instructed to suppress the muscle tension in the same muscle group. The order of administration of enhancement and suppression trials was randomized for each scene. Subjects were given several trials to practice controlling both zygomatic and corrugator EMG. Feedback was available during the practice trials and during the enhancement and suppression trials of the experiment. Continuous monitoring of both zygomatic and corrugator EMG during the study indicated that subjects were successful in altering muscle tension in accord with the experimental instructions, and videotapes of subjects' faces indicated no overt changes in facial responding during imagination of the scenes. Subjects' ratings of emotional responding during each scene indicated that subjects experienced less enjoyment and more distress during positive affective trials in which they suppressed zygomatic EMG activity. The results are discussed in terms of the facial feedback hypothesis.