The Representational Format of Stimulus Intensity

01/12/2023 to 30/11/2026

Project A1 aims at a deeper understanding of the cognitive representation of perceived stimulus intensity, which, for example, allows people to compare stimulus levels across sensory modalities (i.e., cross-modal matching) and perceive differences in stimulus intensities (i.e., discrimination). We combine two psychophysical approaches to address this issue from a broader empirical and theoretical perspective. The first approach seeks to rigorously investigate the long-standing assumption that cross-modal correspondences are absolute, mediated by an amodal representation. The theory of global psychophysics dissociates the underlying correspondences from decision processes related to respondent-generated internal references, which may explain the observed context dependence of cross-modal judgments. This abstract mathematical theory is necessarily agnostic regarding the physical mechanisms underlying intensity perception. Hence it is supplemented by a second, neurobiologically inspired approach derived from reaction time research. This second approach assumes that the frequency of neural firings in stimulus-generated pulse trains is the cognitive currency of perceived intensity. Common to these two approaches is the hypothesis that a single representation of stimulus intensity is shared across all sensory modalities. In this regard, the representation is amodal because the same encoding strategy is used irrespective of sensory modality.