In 13 milliseconds (13 one-thousandths of a second), a hummingbird can flap its wings a few times – and your brain can comprehend a picture, scientists say.
That’s a new finding from Massachusetts Institute of Technology researchers, who outline evidence of our brains’ hyperactive processing capabilities in a paper recently published in the journal Attention, Perception, and Psychophysics. The results represent a significant reduction of an earlier estimate that image processing takes around 100 milliseconds for the brain.
"The fact that you can do that at these high speeds indicates to us that what vision does is find concepts,” senior author Mary Potter said in a statement. “That's what the brain is doing all day long — trying to understand what we're looking at.”
Potter and her colleagues clocked the brain’s image-processing speed using a technique known as “rapid serial visual presentation,” or RSVP. Study participants were shown a series of six or 12 images that flashed on a screen for very brief timeframes. Participants were told to watch for a particular kind of picture (“smiling couple”) appearing in the sequence. The researchers kept decreasing the time the picture stayed on the screen in successive trials – from 80 milliseconds, to 53, then 40, then 27, and then to 13 (the fastest possible rate they could show images with their computer monitors).
Initially, the team hadn’t expected the subjects to be able to detect the target images much better than chance at speeds below 50 milliseconds. Previous research had suggested this was the cutoff time for visual information to move from the retina and throughout the visual processing areas of the brain, in order to comprehend what is being seen. But, though their performance dropped the quicker the images flashed on the screen, the study subjects were still performing better than expected at lower and lower speeds.
"This didn't really fit with the scientific literature we were familiar with, or with some common assumptions my colleagues and I have had for what you can see," Potter said.
Potter and her team think that part of the reason the subjects performed so well may be that they were honing their skills with those successive trials, after which they received feedback. But the researchers also point to a 2001 study of macaque monkeys in the Journal of Cognitive Neuroscience, which showed that the primates could respond to images presented for just 14 milliseconds.
The next step for the researchers is investigating how long images linger in our brain’s short-term storage. They’ll be using a magnetoencephalography (MEG) scanner during picture-flashing experiments similar to the ones used in the study, to see what areas of the brain are active when people recognize pictures quicker than a blink of an eye.