To provide converging support that the proper integration of analog and propositional representational systems is associated with spatial ability, the visual, auditory, and bimodal brain event-related potentials were recorded from 50 right-handed Caucasian males. Sensory interaction indices were derived for these subjects who had taken the Surface Development Test of spatial ability. Product-moment correlations were computed between sensory interaction indices for eight cerebral sites and spatial ability test scores. Sensory interaction for left and right hemispheric regions was significantly related to spatial ability. As sensory suppression lessened, spatial ability increased. The results substantiated the theory that the visual-imaginal-analog and the auditory-verbal-propositional representational systems are implicated in spatial ability. The extent to which the cortex can inhibit or attenuate the interaction or integration between these dual symbol systems is associated with complicated spatial task performance. (Author)