A study to assess gross and fine motor control within pairs of twins and between twins and singletons found that singletons out-performed twins in motor development. There were no apparent performance differences by sex or between the first- and second-born twins. Research methodology and analysis of data are presented. (DF)

The development of ontogenetic movements--complex, learned skills such as throwing--is greatly influenced by socialization experiences provided by parents. Girls, as well as boys, should be given the opportunity to learn and develop these skills during preschool years. (PP)