Where are the context effects?

Context effects, including attraction, similarity, and compromise effects, have been widely studied. These effects occur when choices among existing alternatives are impacted by adding new alternatives to the choice set. Sometimes the addition of a new alternative impacts the relative choice share (RCS) for one alternative compared to another. In other cases, adding a new alternative simply increases the absolute choice share (ACS) one alternative receives. Here we report a meta-analysis of all three effects asking how reliably, across 23 papers with 29,538 observations, these effects impact the RCS and ACS. The results revealed that these three context effects robustly impacted the RCS of an option. While the attraction and compromise effects only weakly impacted the ACS. Results further showed that the context effects depend on the configuration of attributes across the choice set, yet nearly all the studies to date have focused on a very specific configuration. Furthermore, simulations with leading choice models that predict context effects like MDFT and MLBA make very different predictions about how different configurations of attributes give rise to these effects. Altogether our results establish a great need to map out how these context effects change over a much larger configuration of alternatives.