1. A low level of cortical arousal is desirable for relaxation, hypnosis, and the subjective experience of psychic states and unconscious manifestations.
2. A high level of cortical arousal gives increased powers of reflection, focused concentration, increased reading speed, and increased capacity for long-term recall.
3. Cortical arousal has a simple relationship to skin conductivity. Arousal of the cortex increases the conductivity of the skin and conversely, a drop in arousal causes a drop in skin conductivity. 

from Carl Jung and Jungian Analytical Psychology by Gregory Mitchell