When an organism has a choice between a constant and a variable outcome, both with the same mean value, 'risk' can be assessed by the proportion of times the variable outcome is chosen. Variable amounts of reinforcement and variable delay to reinforcement have been the most commonly studied determinants of risky choice, but no one theory has accounted for the results of both manipulations. Delay-reduction theory (DRT) and the Budget Rule, which both take overall economic context of the choice into effect, are reviewed and compared in a series of studies. Human studies in risky choice show a general pattern of risk aversion. While no one theory can account for this finding, work in the area of Judgment and Decision Making may lead to new avenues of research that fruitfully combine both behavior analytic and cognitive frameworks. Keywords: Risky choice, context, delay reduction, budget hypothesis, decision making. ********** Behavior analysts have studied risk-taking by having subjects choose between constant and variable outcomes, with the same mean value. A central variable influencing such choices with non-human subjects is the reinforcement dimension that is manipulated. When the choice is between a constant and variable delay until reinforcement (reinforcer-delay risk) non-human subjects consistently prefer the variable alternative. In the first demonstration of this effect, Herrnstein (1964) asked pigeons to choose between an outcome providing reinforcement on a fixed-interval (FI) 15-second schedule in which food occurred for the first response after 15 seconds, and an outcome providing reinforcement on a variable-interval (VI) 15-second schedule in which food occurred for the first response after a variable period of time, averaging 15 seconds. Herrnstein found that all four pigeons made approximately 80% of their choice responses to the option leading to the variable delay schedule, indicating risk-prone behavior. Such risk-preference with reinforcer-delay risk has been found despite differences in procedures, reinforcement schedules, types of reinforcement, and the species under investigation (Ahearn, Hineline, & David, 1992; Bateson & Kacelnik, 1995a, 1997; Case, Nichols, & Fantino, 1995; Cicerone, 1976; Davison, 1969, 1972; Frankel & Vom Saal, 1976; Gibbon, Church, Fairhurst, & Kacelnik, 1988; Hursh & Fantino, 1973; Kendall, 1987a, 1989; Killeen, 1968b; Logan, 1965; Morris, 1986; Navarick & Fantino, 1975; Pubols, 1962b; Rider, 1983; Sherman & Thomas, 1968; Zabludoff, Wecker, & Caraco, 1988). These results generated a search for an averaging principle that might unify all of the relevant findings concerning risky choice with delay. Thus, Killeen (1968b) proposed harmonic averaging whereby when the harmonic mean of the components making up the variable outcome equaled the fixed outcome the two outcomes would be equally preferred. This elegant approach accounted for much but not all of the data. For example, in Fantino's (1967) study of preference for fixed-ratio versus mixed-ratio schedules, geometric averaging appeared appropriate. Duncan and Fantino (1970) proposed that the appropriate transforming principle itself depended on molecular characteristics of the schedules being studied. In any event, while no agreement was achieved on a unifying averaging principle, Grace's (1994) contextual choice model (CCM) of choice in concurrent-chains schedules served as a general model of choice that provided a satisfactory account of preference for variable delays. If the non-human subject is given a choice between a fixed and variable amount of reinforcement (reinforcer-amount risk), the results are less clear. A majority of studies have found evidence that subjects are risk averse (e.g., Barkan, 1990; Battalio, Kagel, & MacDonald, 1985; Caraco, 1982; Caraco & Lima, 1985; Hamm & Shettleworth, 1987; Logan, 1965; Menlove, Inden, Madden, 1979). …