Phasic alertness and differences in picture encoding speed.

The relation between physical identity and name identity encoding speed was assessed. Correlational analyses indicated that similar processes may be involved in the two types of encoding and, by implication, that differences between mentally retarded and nonretarded subjects' physical identity and name identity encoding speed may result from common factors. Also, we assessed the extent to which differences in preparation for the presentation of external stimuli may account for any observed differences in encoding speed. A difference between retarded and nonretarded subjects in preparation time was apparent; however, this difference did not influence encoding speed.