Development of stepping patterns in human infants: a dynamical systems perspective

Upright locomotion has been, perhaps, the most studied of all human motor behaviors. The acquisition of this motor milestone has been of major interest to developmentalists from the motor as well as the cognitive domains. Until recently, developmentalists have chosen a nonexperimental approach, opting instead to describe the motor behaviors that precede walking, assigning them precursor status, and attributing the sequence solely to maturation of the nervous system. In this paper, I will discuss evidence that suggests that we may better understand this and other aspects of motor development by viewing them from the theoretical perspective of nonlinear and complex dynamical systems. Focus will be on the availability of a coordinated and alternating stepping pattern throughout much of the first year of life. Factors that influence the expression of and variability in this movement pattern will also be discussed. In addition, I will address the need to understand the development of control of pattern formations as well as their coordination, and I will discuss one approach that may provide some insight; that is, to study the modulations and patterns of muscle and other forces underlying limb movements.     

The role of propulsive muscles of the shoulder during quadrupedalism in vervet monkeys (Cercopithecus aethiops): implications for neural control of locomotion in primates

In comparative anatomical studies of the shoulder, the humeral retractors are often grouped together as propulsive muscles, which are important in the propulsive stroke of the forelimb during quadrupedal locomotion. Electromyographic (EMG) analyses of these muscles in opossums, cats, and dogs in general have confirmed such conclusions. An EMG study of chimpanzee shoulder muscles during knuckle-walking found, however, that the humeral retractors are either inactive or perform a function unrelated to propulsion (Larson & Stern, 1987). This contrast in muscle recruitment patterns between chimpanzees and more "typical" mammalian quadrupeds was attributed to the derived morphology of the chimpanzee shoulder. The present study examines the activity patterns of the humeral retractors in the vervet monkey, a primate more closely resembling nonprimate mammals in its shoulder morphology. The results of this EMG analysis show that despite the significant differences in anatomy between chimpanzees and vervets, the two species display very similar muscle recruitment patterns during quadrupedalism, and there is evidence for this same pattern in other species of primates. These differences in muscle activity patterns between primates and nonprimate mammals may be related to changes in the neurological control of locomotion in primates due to the evolutionary development of manipulative abilities in the primate forelimb.     

Autobiographical memory in a case of multiple personality disorder

Previous research on multiple personality disorder (MPD) has been concerned with between-personalities amnesia, and little attention has been paid to within-personality memory function. This study examined the autobiographical memory of a multiple personality patient, I.C., with cueing procedures that have proven useful in previous studies of normal and abnormal memory. Results indicated that I.C. was able to retrieve autobiographical episodes from the recent past, although her performance differed in several respects from that of matched controls. The study also revealed a striking deficit in I.C.'s autobiographical memory for childhood: She was unable to recall a single episode from prior to the age of 10 in response to various retrieval cues, whereas control subjects had no difficulty recalling numerous childhood episodes. This phenomenon of extended childhood amnesia has not been reported previously in studies of MPD.     

Occupational Representativeness and Prestige Rating: Some Observations

The authors examine occupational representativeness for its effect on prestige ratings. Compositions of occupational listings do not affect ratings. Career counseling implications are noted.     

Developmental levels of processing in metaphor interpretation

We outline a theory of metaphor interpretation. The theory posits varying levels of semantic processing and formalizes them in terms of kinds of semantic-mapping operators that transform properties of the metaphoric vehicle (i.e., predicate) into properties of the metaphoric topic (i.e., subject). We used cognitive-developmental theory to estimate the mental-processing complexity of the various mapping operators, and thereby to predict the timing of their emergence in childhood, and to construct a measure of the metaphoric-processing levels. Metaphor interpretations collected from children (aged 6-12 years) and adults were coded and scored according to the processing levels. In two separate developmental studies, processing score increased with age in a predictable way. Growth in a mental-attentional resource accounted for much of the developmental variance in metaphor interpretation. Possible moderating effects of knowledge and context are discussed.     

Is dependence on phonological information in children's reading a product of instructional approach?

Eight-year-old British children were found to be less accurate at rejecting pseudohomophones than ordinary nonwords in a lexical decision task, but 8-year-old New Zealand children did not show this effect. A subsequent homophone decision task showed that this difference was not due to the New Zealand children being unable to distinguish pseudohomophones from other nonwords. The New Zealand children, however, were less accurate than the British children in pronouncing the pseudohomophones they had identified. It was argued that the British children tended to sound out the items before making a choice in the lexical decision task, which gave salience to phonological rather than visual information, resulting in increased errors to the pseudohomophones. It was concluded that where the British children showed this dependency on use of phonological information it was a product of the teaching approach they had experienced.     

Metamemory, memory performance, and causal attributions in gifted and average children

Fifth and seventh graders who had been teacher-selected as high- or average-achieving were tested on the Kognitiver F?higkeits Test, a standardized test of intellectual abilities for German children. Children who met preestablished criteria as gifted or average were then tested on measures of metacognitive knowledge, attributional beliefs, and performance on a sort recall task. Results indicated ability-related differences in metamemory and sort recall performances. Responses to the attributional questionnaires also varied systematically according to ability: gifted children were more likely to attribute their academic successes to high ability than were average children, who showed a stronger belief in the importance of effort in determining task outcomes. Causal modeling analyses illustrated the strength of metacognitive knowledge as a performance predictor on the memory task, especially for average children. Results are discussed in terms of the value of metacognitive theory in understanding individual performance differences.     

Cheating following success and failure in heavy and moderate social drinkers

Two groups of American undergraduates (moderate and heavy social drinkers) completed a matrix task and received either positive or negative feedback on their performance. Following this they were given a maze task, which was designed so that cheating could be detected. Heavy drinkers cheated more than moderate drinkers under success conditions (positive feedback). Heavy drinkers who received positive feedback also cheated more than heavy drinkers who received negative feedback. The results are interpreted in terms of self-handicapping theory.     

Improving cognitive search skills in resistant hypnotic subjects

Subjects who were resistant (n = 20) and susceptible (n = 20) to hypnotic suggestion were asked to find the letter Z in an array of other straight-form letters. Susceptibles found the letter more quickly than resistants, and this superiority appeared to be related to their use of a more efficient search strategy. When resistants were taught this strategy, their performance was not significantly different from that of susceptibles. Implications of these results for teaching search strategies are discussed.