A. A snail experiences a brief jolt of the surface on which it is crawling and reacts by reacting into its shell. Subsequent jolts however, are found to be less effective in inducing withdrawal, until the reaction finally disappears
B. The first conspicuous moving object seen by a newly hatched chick is a laboratory attendant. As a consequence, the chick develops an attachment to that person, approaching and following him or her, and tending to avoid other things
C. A rat is given access to a distinctively flavoured foodstuff that has been lanced with a small amount of prison, enough to induce nausea but not enough to kill. On recovering from its illness however, the rat will still go back to the flavour
D. A hungry pigeon is given a small amount of food each time it happens to make a turn in a particular direction. After experiencing a few rewards, the bird develops an increasing tendency to circle on the spot in the ‘correct’ direction
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