Context effects on choice under cognitive load

The context-dependent nature of choice is well illustrated by decoy effects, in which adding an alternative to a choice set can change the preference relations among the other alternatives. The current within-subjects study tested whether manipulating cognitive load affects the magnitude of attraction and compromise decoy effects. Participants (n = 96) made simulated online grocery shopping choices from three options described by price and quality for each grocery item they encountered. On half the 96 trials, they had to memorize a telephone number prior to encountering the choice set, after which they recalled the number. The choice task was rated significantly more difficult under load, providing some face validity for the load manipulation. Across decoy types, context effects were large and unaffected by the load manipulation. Bayesian analysis provided substantial evidence in favor of this null effect, with the study powered at better than .95 to detect a moderate effect. Across individuals, the magnitude of decoy effects was positively correlated with perception of the greater difficulty of the task under load, with this relationship fully mediated by increases in response times. These results are consistent with the idea that compromise and attraction decoy effects can operate relatively automatically and require minimal effortful processing.