Subjects were asked to walk to targets that were up to 21 m away, either with vision excluded during walking or under normal visual control. Over the entire range, subjects were accurate whether or not vision was available as long as no more than approximately 8 sec elapsed between closing the eyes and reaching the target. If more than 8 sec elapsed, (a) this had no influence on distances up to 5 m, but (b) distances between 6-21 m were severely impaired. The results are interpreted to mean that two mechanisms are involved in guidance. Up to 5 m, motor programs of relatively long duration can be formulated and used to control activity. Over greater distances, subjects internalized information about the environment in a more general form, independently of any particular set of motor instructions, and used this to control activity and formulate new motor programs. Experiments in support of this interpretation are presented.

The way in which gait is regulated to meet the demands of the terrain was investigated by analyzing the movements of skilled long jumpers during their run-up to the takeoff board. The analysis revealed that the run-up consists of two phases: (a) an initial accelerative phase, ending about 6 m from the board, during which athletes attempt to produce a stereotyped stride pattern; and (b) a zeroing-in phase, during which they adjust their stride pattern to eliminate error that has accrued. Further analysis revealed that the athletes were regulating a single gait parameter-the vertical impulse, or lift, of their steps. During the stereotyped approach phase they tried to maintain a constant impulse, thereby keeping flight and swing-through time constant. During the zeroing-in phase, they adjusted their flight times (and hence their stride lengths) by regulating the impulse of their steps. The essence of their skill thus appears to lie in the precise adjustment of the impulse toward the end of the run-up. The nature of the visual information that might be used to make the adjustments is discussed.Although research has increased our understanding of the biomechanics of locomotion and of some of the underlying neurophysiological mechanisms (Alexander &

No abstract

The roadside crossing judgments of children aged 7, 9, and 11 years were assessed relative to controls before and after training with a computer-simulated traffic environment. Trained children crossed more quickly, and their estimated crossing times became better aligned with actual crossing times. They crossed more promptly, missed fewer safe opportunities to cross, accepted smaller traffic gaps without increasing the number of risky crossings, and showed better conceptual understanding of the factors to be considered when making crossing judgments. All age groups improved to the same extent, and there was no deterioration when children were retested 8 months later. The results are discussed in relation to theoretical arguments concerning the extent to which children's pedestrian judgments are amenable to training.

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This study investigates the ability of children between 5 and 11 years to select safe places to cross the street. The children were presented with situations which were either extremely safe or manifestly dangerous and were asked to correctly identify these. In other cases, they were asked to choose for themselves routes across the road which they thought would be safe. The tasks were presented in various ways: by means of a table-top simulation on which traffic scenarios had been contrived; by means of photographs of road situations; and by taking the children to real-world sites in the streets near their schools. All the experiments showed a similar pattern of results. Five- and 7-year-olds exhibited very poor skill in identifying dangerous road-crossing sites. Their judgments relied exclusively on the visible presence of cars in the vicinity. Other factors such as blind summits, obscuring obstacles or complex junctions were never recognized as threatening situations. They also showed an unwillingness to make detours when planning their own routes, even where the direct route was manifestly dangerous. Nine-year-olds showed a higher level of ability and 11-year-olds showed quite good skill in these judgements. No sex differences were apparent. These results suggest that young children up to about 9 years must often be at considerable risk as they do not have the ability to recognize a location as dangerous, even if they know the mechanics of the Green Cross Code. The implications for road safety education are discussed.

No abstract

It was hypothesized that practical training is effective in improving children's pedestrian skills because adult scaffolding and peer discussion during training specifically promote E3 level representation (linguistically-encoded, experientially-grounded, generalizable knowledge), as defined by Karmiloff-Smith's (1992) representational redescription (RR) model. Two studies were conducted to examine in detail the impact of this social input in the context of simulation-based training in roadside search skills. A group of 5-8-year-olds were pre-tested on ability to detect relevant road-crossing features. They then participated in four training sessions designed to promote attunement to these, under peer discussion versus adult guidance conditions (Study 1), and adult-child versus adult-group conditions (Study 2). Performance at post-test was compared with that of controls who underwent no training. Study 1 found that children in the adult guidance condition improved significantly more than those in the peer discussion or control conditions, and this improvement was directly attributable to appropriation of E3 level representations from adult dialogue. Study 2 found that progress was greater still when adult scaffolding was supplemented by peer discussion, with E3 level representation attributable to the children's exploration of conflicting ideas. The implications of these findings for the RR model and for practical road safety education are discussed.