A 45-MINUTE RECORDING OF THE DISPUTE -- A MODIFIED VERSION OF AN ACTUAL HEARING RECORDED BY THE AMERICAN ARBITRATION ASSOCIATION -- WAS PLAYED FOR 60 ARBITRATORS (30 MANUFACTURERS, 30 BROKERS) IN 20 3-MEMBER PANELS. THE PANELS DELIBERATED UNTIL THEY SETTLED THE DISPUTE. AS HYPOTHESIZED, THE ARBITRATORS' CHOICE OF THE CENTRAL ISSUE IN THE DISPUTE AND HOW THEY PERCEIVED THE EVIDENCE WERE THE PRIMARY DETERMINANTS OF THEIR DECISIONS. THE ARBITRATORS' DECISIONS WERE PREDOMINANTLY RATIONAL IN TERMS OF HOW THEY VIEWED WHAT THE PARTIES DID VIS-A-VIS WHAT THEY SHOULD HAVE DONE DURING THE PERIOD LEADING TO THE DISPUTE. THERE WERE TWO EXCEPTIONS TO THIS RATIONALITY: FOR SOME BROKERS (ONLY IN PANELS CONSISTING OF ALL BROKERS), AFFINITY WITH ONE PARTY IN THE DISPUTE APPEARED TO SHAPE DECISIONS; AND SOME BROKERS FAILED TO UNDERSTAND THE DISPUTE, COULD NOT GRASP THE CENTRAL ISSUE, OR COULD NOT APPLY THE APPROPRIATE FACT-FINDING AND SUBSTANTIVE NORMS TO THE EVIDENCE. IMPLICATIONS OF THE FINDINGS FOR RELATED DECISIONMAKING SITUATIONS -- INCLUDING JURY TRIALS -- ARE DISCUSSED. SUPPORTING DATA ARE INCLUDED. A CONCEPTUAL DISCUSSION OF ARBITRATION DECISIONMAKING IS PRESENTED IN NCJ-47558. (AUTHOR ABSTRACT MODIFIED)