Gait adjustments in older adults: activity and efficacy influences.

Factors that influence gait adjustments in active and sedentary older adults were examined in this study. Fifty-five older adults (60-85 years) completed a series of physical activity and self-efficacy measures (gait, falls) and the Berg Balance Scale (K. O. Berg, S. L. Wood-Dauphinee, J. I. Williams, & B. Maki, 1992). Participants then completed a series of walking trials that included walking with and without obstacles placed in their path. Sedentary older adults adopted a more cautious walking style than active ones, exhibiting shorter step lengths and slower step velocities. Age, physical activity level, balance, and the efficacy measures were all found to be significantly correlated with gait speed. Hierarchical regression analyses indicated that once age, sex, and body mass index were controlled for, gait efficacy had a significant independent effect on gait speed. These results highlight the importance of examining multiple factors when examining the control of gait.

Beyond labeling: the role of maternal input in the acquisition of richly structured categories.

Recent research shows that preschool children are skilled classifiers, using categories both to organize information efficiently and to extend knowledge beyond what is already known. Moreover, by 2 1/2 years of age, children are sensitive to nonobvious properties of categories and assume that category members share underlying similarities. Why do children expect categories to have this rich structure, and how do children appropriately limit this expectation to certain domains (i.e., animals vs. artifacts)? The present studies explore the role of maternal input, providing one of the first detailed looks at how mothers convey information about category structure during naturalistic interactions. Forty-six mothers and their 20- or 35-month-old children read picture books together. Sessions were videotaped, and the resulting transcripts were coded for explicit and implicit discussion of animal and artifact categories. Sequences of gestures toward pictures were also examined in order to reveal the focus of attention and implicit links. drawn between items. Results indicate that mothers provided a rich array of information beyond simple labeling routines. Taxonomic categories were stressed in subtle and indirect ways, in both speech and gesture, especially for animals. Statements and gestures that linked two pictures were more frequent for taxonomically related animal pictures than for other picture pairs. Mothers also generalized category information using generic noun phrases, again more for animals than for artifacts. However, mothers provided little explicit discussion of nonobvious similarities, underlying properties, or inductive potential among category members. These data suggest possible mechanisms by which a notion of kind is conveyed in the absence of detailed information about category essences.

Seeing is believing: children's explanations of commonplace, magical, and extraordinary transformations.

Children's magical explanations and beliefs were investigated in 2 studies. In Study 1, we first asked 4- and 5-year-old children to judge the possibility of certain object transformations and to suggest mechanisms that might accomplish them. We then presented several commonplace transformations (e.g., cutting a string) and impossible events (magic tricks). Prior to viewing these transformations, children suggested predominantly physical mechanisms for the events and judged the magical ones to be impossible. After seeing the impossible events, many 4-year-olds explained them as "magic," whereas 5-year-olds explained them as "tricks." In Study 2, we replaced the magic tricks with "extraordinary" events brought about by physical or chemical reactions (e.g., heat causing paint on a toy car to change color). Prior to viewing the "extraordinary" transformations, children judged them to be impossible. After viewing these events, 4-year-olds gave more magical and fewer physical explanations than did 5-year-olds. Follow-up interviews revealed that most 4-year-olds viewed magic as possible under the control of an agent (magician) with special powers, whereas most 5-year-olds viewed magic as tricks that anyone can learn. In a third study, we surveyed parents to assess their perceptions and conceptions of children's beliefs in magic and fantasy figures. Parents perceived their children as beliefs in magic and fantasy figures. Parents perceived their children as believing in a number of magic and fantasy figures and reported encouraging such beliefs to some degree. Taken together, these findings suggest that many 4-year-olds view magic as a plausible mechanism, yet reserve magical explanations for certain real world events which violate their causal expectations.

As time goes by: children's early understanding of growth in animals.

Beliefs about naturally occurring transformations were examined in children aged 3 to 6 years in 4 experiments. Experiment 1 tested children's understanding that animals (but not artifacts) predictably get larger over time. Experiment 1a examined whether the results obtained in the first experiment could be attributed to an added memory component on the artifact task. Experiment 2 further examined beliefs about the aging of artifacts. In Experiment 3, color and shape (metamorphosis) changes of animals were investigated. At all ages, children appeared to understand that animals get larger and not smaller with age. While older children and adults allowed for rather dramatic changes in the size and shape of animals over the life span if the alternative involved decreasing in size with age, preschool children were less willing to accept these changes. Taken together, the results of these studies suggest that even young preschool children have 2 conceptual insights about natural transformations: that they are lawful and nonrandom, and that they are domain and mechanism specific. Further, children as young as age 3 are able to go beyond the perceptual appearance of animals in making judgments about transformations caused by growth. Implications for children's understanding of personal and species identity are discussed.

Children's understanding of action lines and the static representation of speed of locomotion.

Children's understanding of the static representation of speed of locomotion was explored in 2 experiments. In Experiment 1, 20 7-year-olds and 20 9-year-olds drew pictures of 2 people walking and running at different speeds. Children then made judgments about pairs of unambiguous drawings of a person walking or running, as did a sample of 20 adults. The drawings varied according to whether action lines, background lines, or no lines were present. Children were asked to say which figure appeared to be moving faster. In Experiment 2, 20 7-year-olds, 20 9-year-olds, and 21 adults sorted ambiguous drawings of a person walking and running at different speeds. The pictures again contained action lines, background lines, or no lines. In the drawing task, children more frequently used page position and biomechanical information than action lines to represent fast and slow walking and running. In the judgment task, 7- and 9-year-olds offered equivalent judgments of action lines and background lines, whereas adults distinguished between these pictorial devices. In the sorting task, all subjects distinguished between action lines and background lines and judged that pictures containing action lines looked faster than pictures containing background lines and pictures without lines. Taken together, the results indicate that subjects' judgments were influenced by the form of locomotion and degree of ambiguity in the depicted events they saw. The findings are consistent with the view that different categories of pictorial devices exist, but the effectiveness of each device is contingent upon the perceiver's experience with it and the context in which it appears.

Role of visual information in ball catching.

The present study is concerned with the perceptual information about the body and space underlying the act of catching a ball. In a series of four experiments, subjects were asked to catch a luminous ball under various visual conditions. In general, catching in a normally illuminated room was contrasted with catching the luminous ball in an otherwise completely dark room. In the third and fourth experiments, intermediate conditions of visual information were included. The results suggest that it is possible to catch a ball with one hand when only the ball is visible, but performance is better when the subject has the benefit of a rich visual environment and two hands. The second experiment indicated that subject performance does improve with practice in the dark, but time spent in the darkened room itself doesn't result in a significant decrement in performance. Results of the third study suggest that vision of one's hand does not aid in the performance of this task whereas the presence of a minimal visual frame appears to aid performance. The final study examined the relation between catching performance and body sway under similar visual conditions. Results of this experiment imply that persons who exhibit relatively little postural sway in full-room lighting performed better at this catching task.