The functional origins of speech-related hand gestures.

Many theories of language posit its recent evolution, perhaps contemporaneous with the evolution of Homo sapiens. The embodied language theory, however, in proposing that language includes gestures, provides an avenue for tracing language origins to phylogenetically earlier ancestral species. Here, evidence is presented that the structure of functional hand movements (e.

Hand shaping in the rat: conserved release and collection vs. flexible manipulation in overground walking, ladder rung walking, cylinder exploration, and skilled reaching.

Hand shaping in terrestrial mammals is adapted to many functions including walking, climbing, exploration, and skilled manipulation. Nevertheless, hand shaping is not well described in the rat (Rattus norvegicus) although the species is used to study the evolution of movement, the neural control of movement, and to model impairments that can result from brain injury. In the present study, rat hand movements were examined in standardized tests of overground walking, horizontal or inclined ladder rung walking, exploring a vertical wall of a cylinder, and skilled reaching for food.

Individual differences in skilled reaching for food related to increased number of gestures: evidence for goal and habit learning of skilled reaching.

Skilled reaching in rodents and primate is motorically similar, but success in reaching by rodents is distinctively variable. The source of this variability has not been examined previously. Long-Evans rats were videotaped as they reached for food in 2 different reaching tasks, and endpoint measures of performance were examined in relation to variables previously associated with individual differences, including testing procedures, rehabilitation, movement ability, general locomotor activity, and cortical anatomy.