Value and spatial preferences guide habitual reaching and manual object selection in primates

Abstract

Habits are automatic actions shaped by prior experience, enabling efficient and fast responses in stable environments. While habitual gaze rapidly directs the eyes toward valuable objects, the mechanisms underlying habitual manual choice for reaching and grasping remain unclear. Here we show that macaque monkeys develop habitual manual choices toward previously rewarded objects through multi-day object-value learning, driven by learned value and spatial preferences. This reaching habit persisted without reward and showed shorter latencies than in value-deliberative tasks, consistent with automatic control. Regression analyses further revealed that manual choice was guided by learned object values, whereas visual salience had no effect, unlike gaze habits. Instead, intrinsic spatial preferences continued to bias reaching behavior even after long-term value learning. These findings demonstrate that habitual manual choice arises from the integration of spatial preferences and long-term value memory, defining a distinct mechanism of automatic behavior beyond habitual gaze.