Learning at variable attentional load requires cooperation between working memory, meta-learning and attention-augmented reinforcement learning

Abstract

Flexible learning of changing reward contingencies can be realized with different strategies. A fast learning strategy involves using working memory of recently rewarded objects to guide choices. A slower learning strategy uses prediction errors to gradually update value expectations to improve choices. How the fast and slow strategies work together in scenarios with real-world stimulus complexity is not well known. Here, we disentangle their relative contributions in rhesus monkeys while they learned the relevance of object features at variable attentional load. We found that learning behavior across six subjects is consistently best predicted with a model combining (i) fast working memory (ii) slower reinforcement learning from differently weighted positive and negative prediction errors, as well as (iii) selective suppression of non-chosen feature values and (iv) a meta-learning mechanism adjusting exploration rates based on a memory trace of recent errors. These mechanisms cooperate differently at low and high attentional loads. While working memory was essential for efficient learning at lower attentional loads, enhanced weighting of negative prediction errors and meta-learning were essential for efficient learning at higher attentional loads. Together, these findings pinpoint a canonical set of learning mechanisms and demonstrate how they cooperate when subjects flexibly adjust to environments with variable real-world attentional demands. Significance statementLearning which visual features are relevant for achieving our goals is challenging in real-world scenarios with multiple distracting features and feature dimensions. It is known that in such scenarios learning benefits significantly from attentional prioritization. Here we show that beyond attention, flexible learning uses a working memory system, a separate learning gain for avoiding negative outcomes, and a meta-learning process that adaptively increases exploration rates whenever errors accumulate. These subcomponent processes of cognitive flexibility depend on distinct learning signals that operate at varying timescales, including the most recent reward outcome (for working memory), memories of recent outcomes (for adjusting exploration), and reward prediction errors (for attention augmented reinforcement learning). These results illustrate the specific mechanisms that cooperate during cognitive flexibility.