Mechanics of contingency-based Cognitive Bias Modification: pre-existing bias affects potency of active training but not placebo conditions.
Cognitive Bias Modification (CBM) refers to various computerized training protocols aimed at modifying individuals’ automatic information processing patterns (cognitive biases). CBM protocols are commonly regarded as potential new treatments, targeting cognitive biases believed to be involved in, amongst others, anxiety, depression, substance abuse, disordered eating, pain perception, and insomnia. Designed to reward response tendencies associated with more desired information processing patterns trough repeated practice, CBM tasks tend to rely on a (hidden) contingency between stimulus valence and response rewards. In CBM studies, active training conditions are typically contrasted with control conditions lacking the contingency, often called 50/50 placebo. This report focusses on the wide-spread, and intuitive, notion that pre-existing bias may affect the contingency experienced by an individual engaging in a 50/50 placebo control condition thereby inadvertently rendering the intended placebo condition more potent. Employing probabilistic reasoning we conclude that, contrary to the often-forwarded notion, pre-existing bias cannot increase the potency of a 50/50 placebo condition. In contrast, we arrived at the unforeseen conclusion that lack of pre-existing bias may render an active training condition functionally similar to a placebo condition. In this paper we develop these arguments, review literature with respect to our assumptions, and discuss implications.