Normalizing the crossover effect: enhancement of cognitive attentional processing in schizophrenia.

Thirty male schizophrenic subjects and 20 male control subjects were administered both the classic Rodnick and Shakow reaction time (RT) procedure and a modified experimental procedure using a balanced design in an attempt to enhance cognitive attentional processing and inhibit the crossover effect in schizophrenic patients. The experimental procedure increased the number of predictable trials, provided more information about the task and presented the regular trials in a simple ascending order. Analysis of the RT data showed the typical early schizophrenic crossover and late normal crossover on the standard task, while schizophrenic patients in the experimental condition showed a new finding of statistically significant normalization of the early crossover effect. The results support Shakow's theory of attentional set deficit in schizophrenia and in conjunction with previous findings suggest that separate neuropsychological mechanisms of cognitive preparatory attention and a more automatic form of vigilance attention may, respectively, underlie the regular and irregular procedures of the traditional RT task.