# Humans can use positive and negative spectrotemporal correlations to detect rising and falling pitch

## TL;DR

Humans detect rising and falling pitch by using correlations in sound intensity over time and frequency, similar to how the visual system detects motion.

## Contribution

The study reveals that humans can detect pitch motion using both positive and negative spectrotemporal correlations, analogous to visual motion detection.

## Key findings

- Humans can judge pitch direction from spectrotemporal intensity correlations.
- Negative spectrotemporal correlations create an auditory illusion similar to visual reverse-phi motion.
- Both positive and negative correlations signal pitch direction in real-world speech.

## Abstract

To discern speech or appreciate music, the human auditory system detects how pitch changes over time (pitch motion). Here, using psychophysics, computational modelling, functional neuroimaging and analysis of recorded speech, we ask whether humans can detect pitch motion using computations analogous to those used by the visual system. We adapted stimuli from studies of vision to create novel auditory correlated noise stimuli that elicited robust pitch motion percepts. In psychophysical experiments, we discovered that humans can judge pitch direction from spectrotemporal intensity correlations. Robust sensitivity to negative spectrotemporal correlations is a direct analogue of illusory ‘reverse-phi’ motion in vision, constituting a new auditory illusion. Functional MRI measurements in auditory cortex supported the hypothesis that human auditory processing may employ pitch direction opponency. Linking lab findings to real-world perception, we analysed recordings of English and Mandarin speech and found that pitch direction was signalled by both positive and negative spectrotemporal correlations, suggesting that sensitivity to both types confers ecological benefits. This work reveals how motion detection algorithms sensitive to local correlations are deployed by the central nervous system across disparate modalities (vision and audition) and dimensions (space and frequency).

Vaziri et al. examined how humans detect changes in auditory pitch, revealing that listeners rely on correlations in sound intensity over frequency and time, processing that is reminiscent of visual motion detection.