Erikson is to psychosocial as Freud is to ________________.

Which of the following is a valid statement relating to research concerning genetic influence on cognitive abilities?

a. Fraternal twins have higher correlations on scores of cognitive functioning than do monozygotic twins. b. Different types of cognitive abilities are influenced to the same extent by genetics. c. For general cognitive ability, heritability decreases with age. d. Meta-analyses of variance in IQ scores among twins suggest that 50% of the variance can be explained by genetic differences.

Given the same overall frequency of reinforcement on a fixed and a variable schedule of reinforcement, you should predict that the variable reinforcement schedule will tend to produce

a. more breaks in responding and lower resistance to extinction. b. steadier response rates but lower resistance to extinction. c. more breaks in responding but greater resistance to extinction. d. steadier response rates and greater resistance to extinction.