THE EFFECTS OF SCORE FEEDBACK (OWN OUTCOME VS. BOTH OWN AND OTHER PLAYER'S OUTCOME) AND REWARD (HIGH VS. LOW) ON SS'CHOICE BEHAVIOR DURING 100 TRIALS OF A MODIFIED PRISONER'S DILEMMA GAME WERE STUDIED. 15 MALE DYADS WERE RANDOMLY ASSIGNED TO EACH OF THE 4 EXPERIMENTAL GROUPS. THE RESULTS INDICATED AT LEAST 3 MAJOR EFFECTS:(1) MARKEDLY MORE COMPETITIVE BEHAVIOR WAS DISPLAYED BY SS WHEN THEY WERE ABLE TO COMPARE THEIR OWN CUMULATIVE OUTCOME WITH THAT OF THE OTHER PLAYER,(2) SS PLAYED SIGNIFICANTLY MORE COMPETITIVELY WHEN IN A LOW-AS OPPOSED TO A HIGH-REWARD CONDITION, AND (3) TRIALS DIFFERENTIALLY AFFECTED THE EXPERIMENTAL GROUPS, ESPECIALLY AT THE BEGINNING OF THE GAME. IN ADDITION, THE DATA CONFIRM AGAIN THE NOTION THAT COMPETITION IS THE MORE STABLE GAME STRATEGY.(PsycINFO Database Record (c) 2017 APA, all rights reserved)