The flash-lag effect is difficult to explain, but amazingly cool to see. Over at Mixing Memory, Chris has a great post where he links to two examples of the phenomenon and discusses what might be causing it. Cool, isn’t it?
I can’t resist linking to one more example, created by none other than CogDaily’s own Greta Munger. Here are her instructions for seeing the illusion: “Take a look at the movie below, and decide whether or not the blue flashed object is exactly aligned with the end of the gray rod. To start the movie, click on the rod.” Greta discusses the illusion further in this post.
You can see for yourself that the blue object is indeed actually aligned with the rod by using the slider to stop the movie. So why do we see the illusion of the flashing object trailing the moving object? Chris has a couple possible explanations:
Whitney and Murakami argue that the illusion is due to differences in the amount of time it takes to process a flash vs. motion (the latency difference hypothesis). Motion, they argue, gets processed faster, and therefore the perception of the motion biases the later processing of the flash, even though the flash actually occurred first (in other words, the visual system ain’t psychic, it’s just slow).
[Another] theory argues that the illusion is the result of postdiction (as opposed to prediction). Under this view, the visual system uses both pre- and post-flash motion cues from the object (in the demonstrations above, the rings) to estimate the position of the object, and this results in the object appearing to be ahead of the flash. Evidence for the latency difference hypothesis (which involves postdiction as well) is also consistent with the postdiction hypothesis.
I can’t offer any more light on the phenomenon than this, but since it’s one of Greta’s particular areas of expertise, I’ll see if I can get her to respond in the comments (though since she’s just returned from Psychonomics, she may not have time to get to it today).
In other news:
- Greg Henriques attempts a unified definition of “psychology”
- AlphaPsy explains why there may be no such thing as “general intelligence”
- Brain Hammer, a new (to me) neurophilosophy blog (via Mind Hacks). Looks to be a good one.
- Self-healing robot. Be sure to check out the movies. Now we know how the Terminator kept on moving even after being smashed by a truck!