In business, do nice guys finish first or last? In baseball, there is an old saying that ‘‘nice guys finish last.’’ Is this true in the business world? Researchers at Harvard University attempted to answer this question and reported their results in Nature (March 20, 2008). In the study, Boston-area college students repeatedly played a version of the game ‘‘prisoner’s dilemma,’’ where competitors choose cooperation, defection, or costly punishment. (Cooperation meant paying 1 unit for the opponent to receive 2 units; defection meant gaining 1 unit at a cost of 1 unit for the opponent; and punishment meant paying 1 unit for the opponent to lose 4 units.) At the conclusion of the games, the researchers recorded the average payoff and the number of times cooperation, defection, and punishment were used for each player. The scattergrams (p. 102) plot average payoff (y) against level of cooperation use, defection use, and punishment use, respectively.

(a) Consider cooperation use (x) as a predictor of average payoff (y). Based on the scattergram, is there evidence of a linear trend?

(b) Consider defection use (x) as a predictor of average payoff (y). Based on the scattergram, is there evidence of a linear trend?

(c) Consider punishment use (x) as a predictor of average payoff (y). Based on the scattergram, is there evidence of a linear trend?

(d) Refer to part c. Is the slope of the line relating punishment use (x) to average payoff (y) positive or negative?

(e) The researchers concluded that ‘‘winners don’t punish.’’ Do you agree? Explain.