What is the difference between a main effect and an interaction effect?

Come up with and describe a study using the constructs of religion and health (it does not have to be a true experiment). Be specific about how would measure each construct.

Give one operational definition for the construct of motivation.

Is it ever possible for research psychologists to make claims about causality (ie A causes B)? If so, what conditions must be met?

A friend of yours regularly visits a psychic for guidance. Your friend insists this practice is legitimate and begins to list the things he was told by his psychic that turned out to be true (even though he has been told so many more things, most of which did not turn out to be true). What kind of social cognition bias does this represent, and why?