6.9 Indicate whether the following generalizations suggest a positive or negative relationship. Also, speculate about whether or not these generalizations reflect simple cause-effect relationships.

(a) Preschool children who delay gratification (postponing eating one marshmallow to win two) subsequently receive higher teacher evaluations of adolescent competencies.

(b) College students who take longer to finish a test perform more poorly on that test

(c) Heavy smokers have shorter life expectancies.

(d) Infants who experience longer durations of breastfeeding score higher on IQ tests in later childhood.

*7.6 After a group of college students attended a stress-reduction clinic, declines were observed in the anxiety scores of those who, prior to attending the clinic, had scored high on a test for anxiety.

(a) Can this decline be attributed to the stress-reduction clinic? Explain your answer.

(b) What type of study, if any, would permit valid conclusions about the effect of the stress-reduction clinic?