# Humans exhibit associative symmetry in the absence of backward training and stimulus overlap

## TL;DR

This study shows that humans can exhibit associative symmetry without backward training or overlapping stimuli, addressing common issues in previous research.

## Contribution

The study introduces an improved method for testing associative symmetry in humans, eliminating common confounding factors.

## Key findings

- Participants showed robust symmetry in associative networks without backward training.
- Removing temporal overlap between stimuli did not eliminate symmetry effects.
- Symmetry was observed in both bidirectional and unidirectional networks.

## Abstract

A recent survey of the evidence on associative symmetry in humans revealed that nearly all the demonstrations either unintentionally trained backward stimulus pairings and/or had a temporal overlap between the stimuli being trained. We consider these criticisms and improve on our own method of “associative networks.” In this method, participants learn multiple stimulus pairings via arbitrary matching‐to‐sample tasks in which the stimuli are concurrently presented as sample and comparison stimuli. In Experiment 1, human participants learned a bidirectional network (in which symmetry was synergistic) and a unidirectional network (in which symmetry was antagonistic) or two unidirectional networks (removing explicit reinforcement of backward stimulus pairings). In Experiment 2, participants learned two unidirectional networks; however, we removed the temporal overlap between sample and comparison stimuli by imposing a 1‐s delay between them. Both experiments showed robust evidence of symmetry, suggesting that the expression of symmetry in humans survives the most common confounds in published research.