Visual Imagery in Deductive Reasoning: Results from experiments with sighted, blindfolded, and congenitally totally blind persons

Visual Imagery in Deductive Reasoning: Results from experiments with sighted, blindfolded, and congenitally totally blind persons Markus Knauff (markus.knauff@tuebingen.mpg.de) Max-Planck-Institute for Biological Cybernetics Tubingen, Germany Elisabeth May (elisabeth.may@mail.uni-oldenburg.de) Department of Psychology, University of Oldenburg Oldenburg, Germany plays a role in reasoning (e.g. Sternberg, 1980, Richardson, 1987; Johnson-Laird, Byrne, & Tabossi; 1989; Newstead, Pollard, & Griggs, 1986). In Knauff and Johnson-Laird (2000; 2002) we argued that a possible resolution of the inconsistency in the previous results is that these studies have overlooked the distinction between visual images and spatial representations (e.g. Ungerleider & Mishkin, 1982; Logie, 1995; Smith et al., 1995). We conducted a series of experiments to test this hypothesis. We initially accom- plished rating studies to identify a set of verbal relations that varied in the ease of constructing visual images and spatial representations from it. Their results yielded three sorts of verbal relations: 1. visuospatial relations that are easy to envisage visually and spatially; e.g. above – below; 2. visual relations that are easy to envisage visually but hard to envisage spatially, e.g. cleaner – dirtier; 3. control relations that are hard to envisage both visually and spatially, e.g. smarter – dumber From the three sorts of verbal relations we constructed a set of three-term- and four-term-series problems. In three experiments, visual relations such as cleaner and dirtier significantly impeded the process of reasoning in compari- son with control relations such as smarter and dumber. In contrast, visuospatial relations, such as front and back, which are easy to envisage visually and spatially, speeded up the process of reasoning in comparison with control rela- tions (Knauff & Johnson-Laird, 2002). In a subsequent neuroimaging study (fMRI) we showed that in the absence of any correlated visual input, all types of reasoning prob- lems evoke activity in spatial areas of the brain (right supe- rior parietal cortex, and bilaterally in the precuneus), but that only the problems based on visual relations also acti- vated early visual areas corresponding to V2 (Knauff, Fangmeier, Ruff, & Johnson-Laird, 2003). We explained the findings by an interplay of visual images and spatial repre- sentations. For example, given the premises: The cat is above the ape. The dog is below the ape. the participants construct a spatial array representing the relative positions of the three individuals: Abstract We report three experiments on visual mental imagery in de- ductive reasoning. Reasoning performance of sighted partici- pants was impeded if the materials were easy to envisage as visual mental images. Congenitally totally blind participants did not show this visual-impedance effect. Blindfolded par- ticipants with normal vision showed the same pattern of per- formance as the sighted. We conclude that irrelevant visual detail can be a nuisance in reasoning and impedes the process. Introduction Various sorts of evidence are compatible with the conjecture that visual mental imagery is a vital part of human cogni- tion, including the famous studies of the mental rotation and the mental scanning of images (Shepard & Cooper, 1982; Kosslyn, 1980). The aim of the present paper, however, is to show that visual mental imagery is not necessary in reason- ing. It can even be a nuisance in reasoning and impedes the process. The article is motivated by the distinction between visual and spatial representations and processes that has been introduced by Ungerleider and Mishkin (1982). In ad- dition, the article is motivated by studies showing that con- genitally totally blind persons are as good as sighted in the construction and application of spatial representations (e.g. Kerr, 1983), but differ from sighted people in their use vis- ual images. The paper begins with a brief summary of previous find- ings on imagery and reasoning. We focus on deductive rea- soning, in which the truth of the premises ensures the truth of the conclusion. We then outline our hypothesis regarding the connection between visual images, spatial representa- tions, and congenital blindness. We report three experiments that test this hypothesis. Finally, we draw some general conclusions about visual imagery, spatial representations, and reasoning. An influential study of imagery and deductive reasoning was carried out by DeSoto, London, and Handel (1965), who investigated so-called three-term series problems, such as “Ann is taller than Beth. ”, “Cath is shorter than Beth”, “Who is tallest? ” and argued that reasoners represent the three individuals in a visual image, and then “read off” the answer by inspecting the image. There are several other authors who argued in the same vein (e.g. Huttenlocher, 1968; Shaver, Pierson, & Lang, 1976; Clement & Falmagne, 1986). Other authors did not find evidence that imagery cat ape dog