A simple technique for correlating film and EMG in locomotion studies

Two recurring problems hampering investigations of muscular activity patterns during locomotion are electrical “noise” and movement artifact in the electromyographic (EMG) signal and proper synchronization of behavioral events to the EMG. A relatively simple technique for achieving these ends is presented. Vigorous locomotor movements of unrestrained animals are recorded on 16-mm film and synchronized with one or more EMGs from selected muscles with little electrical noise or movement artifact interference. The system employs telemetry which is compared to hardwire techniques.     

Fixation and the stereokinetic phenomenon

One of two circles on a rotating disk appears to execute a planetary motion about the other circle. It is shown that the fixated circle serves as the center of rotation for the nonfixated circle. The effect of fixation is absent when polygons replace the circles. However, when one corner of an isolated square is fixated, the remaining corners rotated about the fixated corner. These planetary effects are consistent with the retinal paths followed by the elements of a display during fixation. This is not unlike the failure of position constancy associated with smooth pursuit of linearly moving targets in environments lacking a stationary visual frame of reference. In the present instance, however, the “retinal” responses occur during tracking of circularly moving targets, even in the presence of a visual frame of reference. These results are discussed in relation to the stereokinetic phenomenon. It is also shown that there is a strong interaction between the effects of fixation and the configurational features of the display. When a circle and a square are overlapping on a rotating disk, fixation of the square does not produce the perception of planetary motion. However, when the circle is fixated, the square is readily perceived as executing a planetary path about the circle. The possibility that position constancy in general is attributable to the geometry of the scene rather than to a “discounting” of information about eye movements is mentioned.     

Effect of information feedback upon intertrial consistency of time judgment

Male college students made verbal estimations of time intervals ranging from five to 80 sec on six blocks of five trials. Some subjects were given information feedback (IF) about judgment errors after each trial and the remaining subjects were given no IF. Judgments of the no-IF group changed from initial overestimations to final underestimations of the intervals across blocks of trials. Judgments of the IF group did not significantly change across blocks. In the no-IF group, each block of trials correlated strongest with immediately adjacent blocks; i.e., the correlation matrix had a superdiagonal form. Interblock correlations were weakened by IF, and the superdiagonal form was not obtained in the matrix of the IF group. Previous theories of the superdiagonal form are considered inadequate to explain these results. An alternative hypothesis, based on changing decision criteria with blocks, which IF attenuates, is proposed to explain these data.     

Predicting Perceptions of Victimization

Male and female subjects rated female victims of misfortune after observing videotapes of the victims detailing their injuries to doctors. Contrary to predictions of just wortd theory, subjects derogated culpable victims more than innocent victims. When observers identified with the victim, through political ties, derogation was reduced. It was concluded that responses to victims are described by a balance theory framework in which the observer's relationships to the victim and the victimizing agent determine whether (s)he will react to victims with sympathy or derogation. It was further concluded that these relationships can be predicted from an understanding of the social and political context shared by the perceiver and the victim.