Cognitive Daily

Last week’s post on how sound affects perception of visual events was the most popular post ever on Cognitive Daily, with over 15,000 visits. This was thanks to links from both Fark’s technology page and digg.com. Yet commenters on both sites expressed disappointment with the demo. I wasn’t especially happy with it either, but then again, I didn’t realize that more people would look at that one post than visited the site in all of February last year!

The problem with the movie is that it’s showing two conflicting phenomena. Turn your sound down and watch the movie:

Even though the motion of the ball is the same each time, the shadow cues viewers that the ball “rolls” diagonally across the floor of the box first, then “flies” diagonally across the front of the box. Then the same animation is repeated again. On its own, this is an amazing demo.

But adding sound gives it an additional wrinkle. If you watch the movie with the sound turned on, the audio cues sometimes conflict with the shadows, as I described last week: “In the first two examples, the motion of the ball and shadow is consistent with with the sound effects. In the third example, the shadow suggests that the ball is moving along the ground, but the airplane sound effects might suggest a lift-off and landing. In the final example, the tire skidding suggests motion along the ground, but the shadow again suggests flight.”


In the experiment I described in last week’s post, the visuals never included shadows, so the only cue as to whether the ball is “flying” or “rolling” was the sound. My demo didn’t match the actual experiment, and that’s what all those visitors were unhappy about.

I could have left it at that, but like I said, I’m a sucker. Since the commenters at Digg and Fark were so strident in their criticism of the demo, I’ve created four new movies in which I’ve somewhat crudely photoshopped out the shadow. Let’s see if readers can experience the effect now. Watch each movie with the sound turned up, then indicate whether the ball appears to be rolling or flying. You’ll need to turn the sound up VERY LOUD to hear it. If you don’t hear anything, turn up the volume.

Movie 1

Movie 2

Movie 3

Movie 4

Of course, it’s still possible that these demos won’t work either — they’re quite crude. However, they’re much better than the demos the first time around. Let me know if you have any other thoughts about the experiment or my demos.