Visual imagery can impede reasoning

Visual mental images are an important part of human cognition, and it is natural to suppose that they can help us to reason. Various sorts of evidence are compatible with this assumption, including the well-known studies of the mental rotation and the mental scanning of images (Kosslyn, 1980; Shepard & Cooper, 1982). The aim of the present article, however, is to reexamine this assumption, to reject it, and to propose an alternative hypothesis in its stead. The article is motivated by the distinction between visual and spatial representations and processes that has been made by several researchers (e.g., Johnson-Laird, 1998; Kosslyn, 1994; Landau & Jackendoff, 1993; Rueckl, Cave, & Kosslyn, 1989; Ungerleider & Mishkin, 1982) and is supported by investigations with brain-damaged patients (e.g., Newcombe, Ratcliff, & Damasio, 1987), functional brain imaging studies (e.g., Smith et al., 1995), and experiments on visual and spatial working memory (see the overview in Logie, 1995). In addition, the article focuses on deductive reasoning, in which the truth of the premises ensures the truth of the conclusion, in contrast to inductive reasoning, in which the truth of the premises does not warrant the truth of the conclusion. We begin with a review of previous studies of imagery and deduction and show that they have often overlooked a possible confounding between materials that invoke visual imagery and materials that invoke spatial representations. We then outline our alternative hypothesis that visual images are not critical for deductive reasoning and may even interfere with the process, whereas spatial representations help individuals to reason deductively. We report three experiments that test this hypothesis. Finally, we draw some general conclusions about visual imagery, spatial representations, and reasoning. A pioneering study of imagery and deductive reasoning was carried out by De Soto, London, and Handel (1965), who investigated so-called three-term series problems, such as