Asymmetrical effects of adaptation to left and right shifting prisms depends on pre-existing attentional biases
Journal of the International Neuropsychological Society, 16, 795 – 804, May 2010
Kelly M. Goedert, Ph.D.
Department of Psychology
A. LeBlanc, S. Tsai and A.M. Barrett
Proposals that adaptation with left-shifting prisms induces neglect-like symptoms in normal individuals rely on a dissociation between the postadaptation performance of individuals trained with left- versus right-shifting prisms (e.g., Colent, Pisella, & Rossetti, 2000 ). A potential problem with this evidence is that normal young adults have an a priori leftward bias (e.g., Jewell & McCourt, 2000 ). In Experiment 1, we compared the line bisection performance of young adults to that of aged adults, who as a group may lack a leftward bias in line bisection. Participants trained with both left- and right-shifting prisms. Consistent with our hypothesis, while young adults demonstrated aftereffects for left, but not right prisms, aged adults demonstrated reliable aftereffects for both prisms. In Experiment 2, we recruited a larger sample of young adults, some of whom were right-biased at baseline. We observed an interaction between baseline bias and prism-shift, consistent with the results of Experiment 1: Left-biased individuals showed a reduced aftereffect when training with right-shifting prisms and right-biased individuals showed a reduced aftereffect when training with left-shifting prisms. These results suggest that previous failures to fi nd generalizable aftereffects with right-shifting prisms may be driven by participants’ baseline biases rather than specifi c effects of the prism itself. ( JINS , 2010, 1– 10 .)