a study conducted by datta indirectly supports the idea that memory benefits from sleep. a box was constructed wherein a single rat could move freely from one end to the other. the bottom of the box was made of a steel grate. a light would shine in the box accompanied by a sound. after a five-second delay, an electrical shock would be applied. once the shock commenced, the rat could move to the other end of the box, ending the shock immediately. the rat could also use the five-second delay to move to the other end of the box and avoid the shock entirely. the length of the shock never exceeded five seconds. this was repeated 30 times for half the rats. the other half, the control group, was placed in the same trial, but the rats were shocked regardless of their reaction. after each of the training sessions, the rat would be placed in a recording cage for six hours of polygraphic recordings. this process was repeated for three consecutive days. during the posttrial sleep recording session, rats spent 25.47% more time in rem sleep after learning trials than after control trials.