Lateralized reaching as dynamical symmetry breaking in the bushbaby (Otolemur garnettii): preliminary evidence

Eight bushbabies were subjected to an extensive series of hand preference trials in which they were required to reach for a raisin from a rotating platform approaching from the right- or left-hand side of their visual field. Three principal types of behavior were observed. Several individuals known to be stable in hand preference continued to show a strong preference for a single hand. Another group, including some previously categorized as stable, exhibited "ambidextrous" cross-body reaching behavior. One individual exhibited far more complex behavior, being ambidextrous at low and very high speeds but lateralized at intermediate speeds. A straightforward adaptation of the dynamical neural field theory of Schöner et al. (1997) provides a model allowing each type of behavior, except possibly the shift from lateralized behavior to ambidextrous behavior at high speed, which might nonetheless be accommodated with minor modification.