Visual imagination can influence visual perception – towards an experimental paradigm to measure imagination

Abstract

During visual imagination a perceptual representation is activated in the absence of sensory input. This is sometimes described as seeing with the mind’s eyes. A number of physiological studies indicate that the brain uses more or less the same neural resources for real visual perception and visual imagination. The intensity of visual imagination is typically assessed with questionnaires, while more objective measures are missing. Aim of the present study was, to test a new experimental paradigm that may allow to objectively quantify imagination. For this we used priming and adaptation effects during observation of ambiguous figures. Our perception of an ambiguous stimulus is unstable and alternates spontaneously between two possible interpretations. If we first observe an unambiguous stimulus variant (the conditioning stimulus), the subsequently presented ambiguous stimulus can either be perceived in the same way as the test stimulus (priming effect) or in the opposite way (adaptation effect) as a function of the conditioning time. We tested for these classical conditioning effects (priming and adaptation) using an ambiguous Necker Cube and Letter /Number stimuli as test stimuli and unambiguous variants thereof as conditioning stimuli. In a second experimental condition, we tested whether the previous imagination of an unambiguous conditioning stimulus variant – instead of its observation – can have similar conditioning effects on the subsequent test stimulus. We found no systematic classical conditioning effect on the group level, neither for the cube stimuli nor for the letter/number stimuli. However, highly significant correlations between effects of Real and Imaginary condition were observed for both stimulus types. The absence of classical condition effects at the group level may be explained by using only one conditioning time, which may fit with individual priming and adaptation constants of some of our participants but not of others. Our strong correlation results indicate that observers with clear classical conditioning effects have about the same type (priming or adaptation) and intensity of imaginary conditioning effects. As a consequence, not only past perceptual experiences but also past imaginations can influence our current percepts. This is further confirmation that the mechanisms underlying perception and imagination are similar. Our post-hoc qualitative observations from three self-defined aphantasic observers makes our paradigm a promising objective measure to identify aphantasia.