No Evidence for Expectation Effects in Cognitive Training Tasks

Abstract

A great deal of recent empirical and theoretical work has examined whether it is possible to enhance cognitive functioning via behavioral (cognitive) training. While a growing body of research provides support for such a hypothesis, multiple critiques of the field have suggested that any positive findings in the field to date may be due to placebo effects, rather than reflecting “true” benefits of the training paradigms. Here, in a series of four experiments, we sought to purposefully induce placebo effects of this type in cognitive training-style setup. We did so in multiple outcome domains (fluid intelligence; spatial skills), employed multiple types of “training” paradigms (classic cognitive training using the N-back working memory task; the video game Tetris) and critically, combined explicit verbal instructions that participants in some groups “should” expect to improve their performance after completing their training with associative learning “evidence” that such improvements were occurring (via manipulated task designs). In no case, though, was a placebo effect observed. These results collectively provide evidence against the contention that placebo effects are a major driver of positive outcomes previously attributed to cognitive training interventions.