Brains Still Outperform Computers

Automated financial trading machines can make complex decisions in a thousandth of a second. A human being making a choice – however simple – can never be faster than about one-fifth of a second. Our reaction times are not only slow but also remarkably variable, ranging over hundreds of milliseconds.

Is this because our brains are poorly designed, prone to random uncertainty – or “noise” in the electronic jargon? Measured in the laboratory, even the neurons of a fly are both fast and precise in their responses to external events, down to a few milliseconds. The sloppiness of our reaction times looks less like an accident than a built-in feature. The brain deliberately procrastinates, even if we ask it to do otherwise.

Massively Parallel Wetware

Why should this be? Unlike computers, our brains are massively parallel in their organization, concurrently running many millions of separate processes. They must do this because they are not designed to perform a specific set of actions but to select from a vast repertoire of alternatives that the fundamental unpredictability of our environment offers us. From an evolutionary perspective, it is best to trust nothing and no one, least of all oneself. So before each action the brain must flip through a vast Rolodex of possibilities. It is amazing it can do this at all, let alone in a fraction of a second.

But why the variability? There is hierarchically nothing higher than the brain, so decisions have to arise through peer-to-peer interactions between different groups of neurons. Since there can be only one winner at any one time – our movements would otherwise be chaotic – the mode of resolution is less negotiation than competition: a winner-takes-all race. To ensure the competition is fair, the race must run for a minimum length of time – hence the delay – and the time it takes will depend on the nature and quality of the field of competitors, hence the variability.

Fanciful though this may sound, the distributions of human reaction times, across different tasks, limbs, and people, have been repeatedly shown to fit the “race” model remarkably well. And one part of the brain – the medial frontal cortex – seems to track reaction time tightly, as an area crucial to procrastination ought to. Disrupting the medial frontal cortex should therefore disrupt the race, bringing it to an early close. Rather than slowing us down, disrupting the brain here should speed us up, accelerating behavior but at the cost of less considered actions.