# Neural traces of composite tasks in complex task representation in the human brain reflects learning performance

## TL;DR

This study shows how the brain uses shared simple tasks to speed up learning of new complex tasks, with neural activity reflecting this learning process.

## Contribution

The study demonstrates that neural representations of shared simple tasks support behavioral generalization in complex task learning.

## Key findings

- Participants learned novel complex tasks faster when they shared a simple task with previously learned tasks.
- EEG decoding revealed neural traces of shared simple tasks even when they were not part of the current complex task.
- Decoding strength of shared tasks correlated with both neural association effects and behavioral generalization.

## Abstract

Task knowledge can be encoded hierarchically such that complex tasks can be built by associating simpler tasks. This associative organization supports generalization to facilitate learning of related but novel complex tasks. To study how the brain implements generalization in hierarchical task learning, we trained human participants on two complex tasks that shared a simple task and tested them on novel complex tasks whose association could be inferred via the shared simple task. Behaviorally, we observed faster learning of the novel complex tasks than control tasks. Using electroencephalogram (EEG) data, we decoded constituent simple tasks when performing a complex task (i.e., EEG association effect). Crucially, the shared simple task, although not part of the novel complex task, could be reliably decoded from the novel complex task. This decoding strength was correlated with the EEG association effect and the behavioral generalization effect. The findings demonstrate how task learning can be accelerated by associative inference.

Task knowledge can be organized hierarchically, enabling generalization to novel tasks through shared components. This study shows that participants learned new complex tasks faster when these shared a simple task, and EEG decoding revealed associative representations of these shared tasks, linking neural association strength to behavioral generalization.