It's easy to expose the limited processing power of the human brain. Present someone with a sequence of letters, and ask them to look out for the two numbers that will be embedded among those letters. They'll spot the first one okay, but if the second number comes less than half a second after the first, it is likely they won't spot it – a phenomenon known as the 'attentional blink'.
The reason the blink occurs is that we only have so much processing power, and when the first number appears, we allocate all our resources to that first number, not leaving any processing power to deal with the second number.
Now Heleen Slagter and colleagues have shown that three months intensive meditation training can change all that, by improving our ability to allocate our brain's limited resources.
Seventeen participants were tested on the attentional blink task prior to and then after a three-month intensive meditation retreat, during which they meditated for between ten and 12 hours per day. Any change in their performance was compared with a control group of 23 participants who were interested in learning about meditation, and who practised a little in the week prior to the second attentional blink task.
The participants who went on the meditation retreat, but not the novice controls, showed significantly improved performance on the attentional blink task between the first and second testing sessions. That is, they showed less of an attentional blink, identifying more of the second numbers that appeared in the stream of letters.
Moreover, after their retreat, the experienced meditators tended to show a weaker brain response to the first numbers, as revealed by electroencephalography. In fact, in a neat pairing of brain and behavioural data, it was those participants who showed the greatest reduction in their brain response to the first numbers, who were most accurate at spotting the second numbers. It seems they had learned not to allocate all their mental resources to the first number.
“Through mental training, increased control over the distribution of limited brain resources may be possible,” the researchers said. This is consistent with the fact the Vipassana meditation, practised at the retreat, aims to teach people “a non-reactive form of sensory awareness or 'bare attention'”.
Slagter, H.A., Lutz, A., Greischar, L.L., Francis, A.D., Nieuwenhuis, S., Davis, J.M. & Davidson, R.J. (2007). Mental training affects distribution of limited brain resources. PloS Biology, 5, e138.