PMC

Procedure for aligned outcomes (see for other treatments).

Robustness treatments. Mean number of reported doubles and percentage of (totally) brazen B players per treatment. Mean number of reported doubles (Left vertical axis): the dotted line is the expected number of doubles assuming honesty (3.33); error bars are ±1 SE; mean and SD are at the Bottom of each bar; significance indicators: *P < 0.05.

(A) Simulation of reported outcomes assuming honest reports. Each dot represents the reports of player A and player B in a single trial. The simulation assumes that each number (1 to 6) is reported with a probability of 1/6 in any given trial. The position of dots is jittered to allow visibility of identical outcomes. (B) The observed distribution of reported outcomes in aligned outcomes. Each dot represents the reports of player A and player B in a single trial. The position of dots is jittered to allow visibility of identical outcomes. High values on the diagonal—especially pairs of 6’s—which yield the highest payoffs, are overrepresented.

Four prototypical dyads. The horizontal axis represents the 20 trials; the vertical axis represents the die roll outcomes; an “O” represents player A’s report; and an “X” represents player B’s report. (A) A brazen dyad, reporting a “double 6” 20 times; (B) player A is brazen, player B appears honest; (C) player A appears honest, player B is brazen; (D) corrupt signaling. After mutual reports of 4 in the first five trials, A reported a 4 once more, but B replied with a 6, arguably to suggest to A that switching to higher numbers would be more profitable.

Mean number of reported doubles and percentage of (totally) brazen B players per treatment. Mean number of reported doubles (Left vertical axis): the dotted line is the expected number of doubles assuming honesty (3.33); error bars are ±1 SE; mean and SD are at the Bottom of each bar; significance indicators: *P < 0.05. The number of doubles exceeded the honesty baseline in all treatments. Collaboration on equal terms (aligned outcomes) led to more reported doubles relative to individual behavior. Changes to the payoffs of either A or B had a very similar effect on the number of reported doubles. There were more brazen B players in aligned outcomes than in the other treatments (Right vertical axis).