In operant conditioning, a(n) __________ increases the occurrence of a response.

Ethologist Irenaus Eibl-Eibesfeldt (1963) raised rats in isolation. When other rats were finally introduced into their cages, rats raised alone _______, suggesting that _______.

A) fled from the new rats; aggression must be learned. B) used the same aggressive behaviours as other rats; aggression need not be learned. C) did not aggress against them; instrumental aggression does not exist in nonhumans. D) could not defend themselves; aggression is learned. E) become more aggressive than other rates; isolation leads to aggression.

A person's sex is determined by

nurture during prenatal development. the 23rd pair of chromosomes. the first pair of chromosomes. hormones released during prenatal development.