VLA Policies Do Not Know When Not to Act: Unintended Task Execution and Start Suppression
Overview
This research investigates the behavior of vision-language-action (VLA) policies when given missing, meaningless, or incorrect instructions. Using six model checkpoints in the LIBERO-Goal simulation environment, the authors found that robots consistently initiated movement even with empty inputs and frequently completed unspecified tasks. While a gating mechanism successfully suppressed motion on non-task inputs for five of the six models, fine-tuning approaches failed to reliably keep robots still. The study concludes that current VLA architectures lack the ability to distinguish between valid commands and noise, posing potential risks in real-world deployment where input reliability cannot be guaranteed.
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Environment: simulation
“d protocol with empty, neutral, nonsense, infeasible, and wrong-task instructions to six model checkpoints in LIBERO-Goal simulation. Holding the initial state fixed and varying only the instruction, we ask three questions: whether the robot starts to move, which task it completes, and what the instruction determines. Even when the instruction was empty, the robot started moving in every episode with all six checkpoi”
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- arXiv Robotics — research abstractsSignalVLA Policies Do Not Know When Not to Act: Unintended Task Execution and Start Suppression
This research investigates the behavior of vision-language-action (VLA) policies when given missing, meaningless, or incorrect instructions. Using six model checkpoints in the LIBERO-Goal simulation environment, the authors found that robots consistently initiated movement even with empty inputs and frequently completed unspecified tasks. While a gating mechanism successfully suppressed motion on non-task inputs for five of the six models, fine-tuning approaches failed to reliably keep robots still. The study concludes that current VLA architectures lack the ability to distinguish between valid commands and noise, posing potential risks in real-world deployment where input reliability cannot be guaranteed.
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