Swap the Videos, Break the Model
TL;DR for operators A multimodal model can receive two exercise videos, describe both convincingly, and still fail to determine which person bent the relevant joint further. Apparently, seeing two videos is not the same as comparing them. A minor distinction, unless the product is marketed as a coach. MotionHalluc tests this gap using 1,540 questions constructed from 553 paired fitness videos. Its most revealing experiment simply reverses the query and reference videos while leaving the proposed corrective instruction unchanged. Several models that perform strongly in the expected order collapse when the order is reversed. LLaVA-OV-1.5-8B, for example, falls from 98.39% accuracy to 1.92%. ...