Forty female subjects were given intermittent options to transmit noncontingent promises of intent to cooperate during the course of a mixed-motive laboratory game. In a 2 x 2 experimental design, a robot target either reciprocated subjects' promise statements or concealed her behavioral intentions, and was either always cooperative or always competitive in response to the subjects' promises. Subjects sent more promises to the cooperative than to the competitive robot, and kept their promises more often when the robot reciprocated promises than when the robot used evasive replies. The results were interpreted in terms of normative considerations, with the reciprocal noncontingent promise seen as a contractual commitment tactic in dyadic conflicts. (Author)