Guidelines for quantitative and qualitative studies of sensory substitution experience

Abstract

Information that is normally accessed through a sensory modality (substituted modality, e.g., vision) is provided by sensory substitution devices (SSDs) through an alternative modality such as hearing or touch (i.e., substituting modality). SSDs usually support disabled users by replacing sensory inputs that have been lost, but they also offer a unique opportunity to study adaptation and flexibility in human perception. Current debates in sensory substitution (SS) literature focus mostly on its neural correlates and behavioural consequences. In particular, studies have demonstrated the neural plasticity of the visual brain regions that are activated by the substituting modality. Participants also adapt to using the devices for a broad spectrum of cognitive tasks that usually require sight. However, little is known about the SS experience. Also, there is no agreement on how the phenomenology of SS should be studied. Here, we offer guidelines for the methodology of studies investigating behavioural adaptation to SS and the effects of this adaptation on the subjective SS experience. We also discuss factors that may influence the results of SS studies: (1) the type of SSD, (2) the effects of training, (3) the role of sensory deprivation, (4) the role of the experimental environment, (5) the role of the tasks participants follow, and (6) the characteristics of the participants. In addition, we propose combining qualitative and quantitative methods and discuss how this should be achieved when studying the neural, behavioural, and experiential consequences of SS.