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.