Is Time Moving Forward Or Backward? Computers Learn To Spot the Difference 78
sciencehabit (1205606) writes For the first time, scientists have taught computers to figure out the direction of time in videos, a result that could help researchers better understand our own perception of time. Regardless of any possible applications, "we just thought it was a great problem," says one of the study's authors. Teaching computers to see the arrow of time combines computer science, physics, and human perception to get at the heart of the question, "How do we understand the visual world?"
The researchers "broke down 180 YouTube videos into square patches of a few hundred pixels, which they further divided into four-by-four grids. Combining standard techniques for discovering objects in still photographs with motion detection algorithms, the researchers identified 4000 typical patterns of motion, or 'flow words,' across a grid’s 16 cells. ... When they tested their program on the remaining 60 videos, the trained computers could correctly determine whether a video ran forward or backward 80% of the time."
Abrupt transitions in optical flow? (Score:4, Informative)
Dr Freeman spoke about this work at CVPR this week. In the videos I saw he identified small markers of temporal transition as indicative of moving forward or backward. Those they labeled as backward appeared to recognize asymmetric movement -- as in gradual acceleration followed by sudden deceleration as uniquely forward flow (as when a hand swings down and strickes a table top) -- an asymmetry that cannot occur in reverse (as in sudden acceleration followed by gradual deceleration).
Dr Freeman did not propose this as the causal phenomenon in question, but that made the most sense to me in light of the motions he identified as evidence for backward motion.