Evidence from unilateral lesions of early uncompensable implementation of opposed response-biases in each hemisphere of the brain

PURPOSE: The intact right hemisphere presents an omissive response-bias and the left hemisphere a commissive response-bias in adults. This research sought to determine whether these hemispherically lateralized response-biases manifest early developmental and uncompensable brain implementation. METHODS: Sixteen teenager and adult participants with focal left hemisphere lesions and fourteen with focal right hemisphere lesions (all with childhood onset: M = 13 year recovery period) and 14 normal control participants were recruited. A computerized multitask high order working memory procedure was designed to generate many errors of omission and of commission. RESULTS: The expected double dissociation of response-bias distortion as a function of lesion side was significantly demonstrated on this task and was significantly frontal-lobe dependent. CONCLUSION: The hemispheres of the brain have an opposed response bias that is robustly implemented in infancy through adulthood.