Almost anything that we like to do - eat, shop, gamble, have sex - contain the potential for psychological and physiological dependence.

First of all, the brain and its subsequent physiological reaction.

Thus, all three explanations—physiological maturation, hearing and producing stories about past events, and improved encoding of key aspects of events—seem likely to be involved in overcoming infantile amnesia.

One involves physiological changes relevant to memory.

Yawning did nothing special to their state of physiological activity.

Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict.

Of all the physiological differences in human sleep compared with wakefulness that have been discovered in the last decade, changes in respiratory control are most dramatic.

Avoidance behavior occurs whenever physiological and morphological adaptations are insufficient to maintain body temperature within the vital range.

Physiological adaptations can assist amphibians in colonizing habitats where extreme conditions prevail.

These are automatic, physiological responses too.