Six robot policies moved even with an empty instruction, and the obvious fix stopped none of them
AspireAI community · arXiv (cs.RO, cs.AI)
A vision-language-action policy is supposed to act only on a person's instruction or on an intent it explicitly represents. This study paired six LIBERO-Goal checkpoints against empty, neutral, nonsense, infeasible and wrong-task instructions while holding the initial state fixed. With an empty instruction the robot started moving in every episode with all six checkpoints, and with five of them it often completed a task the instruction had not specified. Two GR00T checkpoints let the instruction decide which task ran but not whether the robot moved at all. Three fixes were tried: prefixing a do-not-move instruction stopped the robot in none of the six checkpoints, a gate comparing the first action chunk against the empty-instruction chunk held it in five of six, and fine-tuning to hold still stopped task completion on non-task inputs but did not reliably keep the robot still or suppress the start on infeasible instructions. The honest conclusion is that start suppression is an unsolved problem, not that one prompt fixes it.
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