Altruism or Arousal in the Rat?

If rats are exposed successively to white noise, then to recorded rat squeals, or alternatively to squeals first and then white noise, and if, in both situations, they are allowed to shut off the auditory stimulation by applying pressure on a bar, they will touch the bar more frequently when exposed to white noise. The results indicate that the bar-pressing behavior is the expression of increased activity resulting from the increased stimulation.