Effects of hemispheric asymmetry on electrodermal conditioning in a dichotic listening paradigm.

It was predicted that when an auditive verbal conditional stimulus (CS+), previously associated with an aversive unconditional stimulus (UCS), is presented to the right ear (initial left hemisphere input), in a dichotic listening task, with the CS- simultaneously presented in the left ear, the result would be greater resistance to extinction than when the same CS+ is presented to the left ear (initial right hemisphere input). In the same vein, it was predicted that, when a tonal CS+ is presented to the left ear, greater resistance to extinction would occur as compared with when it is presented to the right ear. During a dichotic test phase, each group was split into two subgroups, and the CS+ and CS- repeatedly were presented simultaneously to each ear. Half of the subjects in each subgroup had the CS+ presented to the left ear. The other half had the CS+ presented to the right ear. Skin conductance responses were recorded from both hands. Results showed significantly larger responding in all groups to the CS+/UCS compound during the acquisition phase. However, during the dichotic extinction phase, the verbal CS+ right-ear subgroup showed significantly larger resistance to extinction as compared with the verbal CS+ left-ear subgroup. No differences were found between the two tonal subgroups.