# Repetition Hampers Flexible Object Manipulation Under Visual Uncertainty

## TL;DR

Repeating object-use tasks under visual uncertainty makes it harder to adapt, suggesting that repetition impairs flexible movement when sensory feedback is unclear.

## Contribution

The study reveals that repetition-induced interference is stronger in object-use tasks requiring ventral stream input under visual uncertainty.

## Key findings

- Repetition caused stronger interference in object-use tasks compared to visually guided reaching.
- Interference was most pronounced when participants had to rely on sensorimotor memories due to unclear visual feedback.
- Results suggest that the ventral stream is more vulnerable to repetition-induced interference in uncertain conditions.

## Abstract

Seemingly simple actions, like reaching for and lifting an object, involve the coordination of distinct neural pathways within the dorsal and ventral streams. These components can be differentially affected by repetition‐induced anterograde interference, where extensive practice on one task impairs performance on subsequent tasks. Repetition leads to rigid movement patterns, making it harder to adapt flexibly to new situations, especially in tasks with sensory uncertainty that require the brain to rely more on past experiences (i.e., sensorimotor memories). To explore this, we tested whether object‐use tasks, which depend on the ventral stream, are more affected by this interference than a simpler reach‐to‐button task with helpful visual cues. Participants completed two tasks: a reach‐to‐button task involving pressing buttons on either side of a symmetrical object and an object‐use task where the same object had a hidden, asymmetric center of mass (CoM). To measure interference, we manipulated how many times participants lifted the object with the weight on one side before switching it to the other side. Our results showed that interference was strongest in the object‐use task, where uncertain visual information forced participants to rely on sensorimotor memories. In contrast, the reach‐to‐button task, supported by helpful visual cues, showed no significant interference. This suggests that tasks relying on the ventral stream are more vulnerable to interference, particularly when sensory feedback is unclear. Our findings highlight how repetition affects different movement types and emphasize the need for a balance between repetition and flexibility in motor learning.

Repetition‐induced interference was magnified in object‐use tasks under visual uncertainty but absent in visually guided reaching. Together with prior work, these findings suggest that repetition hampers flexibility in both dorsomedial‐ and dorsolateral‐guided actions requiring ventral stream input, highlighting how repetition challenges flexible control of prehensile actions under conditions of heightened visual uncertainty.