Moving train illusion: Why zooming in feels like slowing down

Here's a crazy optical illusion documented by renowned psychologist, Akiyoshi Kitaoka, and explained by scientist Mark Changizi. Watch this video to see the speed of a moving image seemingly decrease as we zoom in on it. But why does this happen? You might think the video has been slowed down, but in fact, the speed remains constant. It's our brain playing tricks on us.

The illusion is about something known as optic flow dynamics. The footage, shot from inside a moving train, seemingly alters the train's speed based on the zoom level. With a wide view, the train appears to rush by swiftly. However, as we zoom in, the pace seems to slow, despite the train maintaining a constant speed. Pretty wild!

Changizi explains:

The illusion that speed decreases when zoomed is "because when one focuses on an inner portion of the movie, the optic flow angular speed is slow, and appears to fill one's entitle visual field, which is consistent with overall lower forward speed.

Note: The more zoomed, the more densely packed the overhead rigging appears. So, even though you appear to be moving forward more slowly when zoomed in, the actual rate of rigging flowing by remains constant, consistent with same forward speed in all conditions.

By the way, these optic flow dynamics undergird why we see hosts of illusions. The brain generates a perception of the anticipated next moment, thereby correcting for neural delay.