# Spatial response-code association for loudness but not brightness

## TL;DR

This study found that loudness, but not brightness, is linked to spatial response codes, affecting how people judge sound intensity.

## Contribution

The study provides new evidence that spatial response codes influence loudness perception but not brightness perception.

## Key findings

- Loudness discrimination is affected by spatial response codes in terms of both response time and accuracy.
- Brightness discrimination did not show significant spatial response code effects.
- Cross-modal correlations between auditory and visual intensity discrimination were inconclusive.

## Abstract

Cognitive associations between stimulus intensity and spatial response codes are thought to influence perceptual discrimination. We examined lateral response-set effects on auditory and visual intensity discrimination in a preregistered study with a large sample (N = 98). Participants responded to loud and bright stimuli using a button located to the left or right of the button used for soft and dim stimuli. In the auditory task, stimulus-response (SR)-mapping affected task-averaged error rates (ERs) but not task-averaged response times (RTs). However, loudness predicted response-side differences in both latency (
RTLeft−RTRight
) and accuracy (
ERLeft−ERRight
). By comparison, all tests of brightness discrimination supported the null or were inconclusive. Assessments of cross-modality correlations in SR-mapping effects were also inconclusive. These results replicate prior findings of lateral SR-mapping effects in auditory intensity discrimination and clarify inconsistencies in the visual domain. The lack of SR-mapping effects in brightness discrimination, along with inconclusive cross-modal correlations, challenges the notion of a common spatial processing mechanism for auditory and visual intensity comparison. If such a mechanism exists, its effects on visual judgments appear too subtle to be detected even in a large sample.