This theoretical note highlights the potential importance of considering reward expectancies in the context of individual differences in reward sensitivity. Based on a theoretical analysis of J. A. Gray's reinforcement sensitivity theory (RST) of personality, and consistent with the general principles of RST. it is hypothesized that the empirical relationship between individual differences in reward sensitivity and actual reactions to (experimenter-defined) reward is moderated by reward expectancies. However, contrary to the specific predictions of RST, it is argued that actual reward of a lower value than expected reward leads to a state of frustrative nonreward primarily in reward sensitive (e.g. impulsive) individuals (it may, as a secondary effect, be enhanced in punishment sensitive, anxious individuals); in contrast, RST contents that frustrative nonreward is mediated primarily by punishment sensitivity (anxiety), and is unrelated to reward sensitivity (e.g. impulsivity). Frustrative nonreward can produce complex, and difficult to interpret, personality x reward effects in typical human laboratory experiments; such results often appear in opposition to the theoretical foundations of RST. It is argued that closer attention to the operational definitions of (experimenter-defined) reward, as well as participants' reward expectancies, may lead to greater experimental precision in RST studies. Some directions for future research are outlined. (C) 2002 Elsevier Science Ltd. All rights reserved.
