Mind Games

From Scientific American:

The cost of hiding the logistical details of perception is that we are always a beat behind. The brain must strike a balance. Cognitive psychologist Alex Holcombe at Sydney has some clever demonstrations showing that certain forms of motion perception take a second or longer to register, and our brains clearly can’t wait that long. Our view of the world takes shape as we watch it.

The 80-millisecond rule plays all sorts of perceptual tricks on us. As long as a hand-clapper is less than 30 meters away, you hear and see the clap happen together. But beyond this distance, the sound arrives more than 80 milliseconds later than the light, and the brain no longer matches sight and sound. What is weird is that the transition is abrupt: by taking a single step away from you, the hand-clapper goes from in sync to out of sync. Similarly, as long as a TV or film soundtrack is synchronized within 80 milliseconds, you won’t notice any lag, but if the delay gets any longer, the two abruptly and maddeningly become disjointed. Events that take place faster than 80 milliseconds fly under the radar of consciousness. A batter swings at a ball before being aware that the pitcher has even throw it.

The cohesiveness of consciousness is essential to our judgments about cause and effect—and, therefore, to our sense of self. In one particularly sneaky experiment, Eagleman and his team asked volunteers to press a button to make a light blink—with a slight delay. After 10 or so presses, people cottoned onto the delay and began to see the blink happen as soon as they pressed the button. Then the experimenters reduced the delay, and people reported that the blink happened before they pressed the button.