INDIVIDUAL-DIFFERENCES AND DEVELOPMENT IN WATER-LEVEL TASK-PERFORMANCE

Data from 23 samples of subjects aged 6.5 years to college age were modeled by a binomial mixture distribution which allows for individual differences in probability of successful task performance. At almost every age and for each sex there are two kinds of performers: those with a high probability of task success (accurate performers) and those with a low probability of task success (inaccurate performers). Age-related improvement of performance is not a consequence of children becoming gradually more accurate in task performance. Improvement is due largely to the increasing proportions of subjects that become accurate performers. Between-sex differences in performance are in evidence at all ages. The proportion of accurate performers is larger in males than in females at every age. © 1991.