Effects of task instructions and oscillation frequency on bimanual coordination

Increases in the oscillation frequency of bimanual movements produce a switch from an anti-phase (180° relative phase) to an in-phase (0° relative phase) coordination pattern. This finding is observed when subjects are instructed not to intervene when they feel themselves slipping out of the anti-phase pattern. The question addressed in this study concerned how performance would be affected if subjects were instructed to try to maintain the pattern at all times. This issue was addressed using two separate groups of subjects: one group was given the do not intervene instructions, the other group was told to try to stay with the pattern at all times. Forearm rotations were tested in 15 s trials, paced by an auditory metronome set at 1.0, 1.5, 2.0, 2.5, and 3.0 Hz. Frequency distributions of the point estimates of relative phase were analyzed. The Do not Intervene group replicated previous findings, as indicated by the development of a bimodal histogram of relative phase distributions with increases in oscillation frequency. However, a very different pattern of findings emerged with increases in oscillation frequency for the group told to stay with the anti-phase pattern. Rather than a bimodal distribution being developed, the data maintained 180° as its central tendency — no secondary distribution developed around 0° relative phase. These data suggest that volitional control can over-ride the inherent dynamical tendencies of the motor system.     

A critical review of theS/L reliability index

The meaning and properties of a commonly used index of reliability, S/L,were examined critically. It was found that the index does not reflect any conventional concept of reliability. When used for an identical behavioral observation session, it is not statistically correlated with other reliability indices. Within an observation session, the standardizing measure of Lis beyond the control of the investigator. Furthermore, the reason for the choice of Las the standard is unclear. The role of chance agreement in S/Lis not known. The exact interpretation of the index depends on which observer reports L.Overall the conceptual and mathematical meaning of S/Lis dubious. It is suggested that the S/Lindex should not be used until its nature is shown to be a measure of reliability. Other approaches such as the intraclass correlations and generalizability coefficients should be used instead.The authors are indebted to Johnny Matson for his critique of an earlier version of this paper.     

Spontaneous startle activity in newborn infants

Spontaneous startles have been reported to occur most frequently in quiet sleep, less frequently in active sleep and drowse, and relatively nonexistent in the waking states. These findings may be a result of a focus on infants whose prenatal histories reflect a restricted range of the conditions to which normal newborns are exposed. The present study examined the spontaneous startle behavior of 30 newborn infants characterized by high numbers of obstetric complications and by indicators of prenatal malnutrition, but within the range of normal, healthy newborns. In this sample, startles were not limited to the sleep and drowse states. Because individual differences in a number of neonatal behaviors have been related to autonomic nervous system (ANS) functioning, the different pattern of spontaneous startles observed in this sample may be related to the functional integrity of this system.     

Sensory modality and the word-frequency effect

Two experiments were conducted to examine whether the word-frequency effect in recognition memory is primarily a modality-dependent phenomenon. In the first experiment, the presentation modality of a target word was varied orthogonally during the input of the test phases. In the second, the subjects were forced to process each input word at the letter-byo letter level, thus minimizing the orthographical differences between the high- and low-frequency words. The word-frequency effect was found in every experimental condition and should be considered a modality-independent phenomenon. A semantically based interpretation of this effect was proposed.     

Matrix derivatives with chain rule and rules for simple,Hadamard, and Kronecker products

The differential calculus for scalars is used to develop theorems for a calculus of functions of matrices. No appeal to scalar notation is necessary in the resulting calculus, so that the given chain and matrix product rules have wide applicability to matrix theory and models. The chain and product rules of scalar calculus become a special case of the matrix rules. The methods are illustrated by application to a generalized stochastic process model potentially relevant to long- and short-term memory.     

Debunking a stereotype: The female medical student

The combined research of Horner (1972) and Monahan, Kuhn, and Shaver (1974) has demonstrated the existence of a stereotype of the female medical student as sex-role deviant and disinterested in sex. The present study examined the validity of this stereotype. Male and female medical students' scores on two psychometric measures were compared with the male and female college norms. The stereotype was not supported. Female medical students demonstrated no greater sex-role deviance than did their male counterparts. Furthermore, only male medical students indicated significantly less heterosexual interest than their same-sex norm.The authors wish to thank Dr. David G. Fish, who was involved in the original data collection. Support for the analyses of these data was obtained from Grant Number 607-1034-21 and from a Career Scientist Award, Number 607-1001-22, to the Junior Author.     

Young adults' perceptions of social sex roles across the life span

Fifty male and 50 female undergraduates rated 10 age-sex targets (Boy, Girl, Adolescent Boy, Adolescent Girl, Young Man, Young Woman, Middle-aged Man, Middle-Aged Woman, Old Man and Old Woman) on 12 semantic differential scales. Compared with female targets, male targets were rated higher on potency and activity scales and lower on evaluative scales. Semantic distance between male and female targets showed a curvilinear relationship with target age. Results suggested that young adult subjects perceive that sex-role differences first increase and then decrease across the life span.An earlier version of this article was presented at the convention of the Western Psychological Association in Los Angeles, California, April 1976.