Is Conscious Thought Slower than Unconscious Thought?

Why Does My Brain Do That?

In this series, bestselling neuroscience author Dr Dean Burnett answers Shambles Patreon subscribers questions about their brains. A sort of neuroscientific agony aunt if you will.

Eve writes, Hi Dean, I was the Cosmic Shambles documentary premiere the other night and I had a question about something the biomechanics person (Editors note – It was Dr Matthew Pain) said that maybe you can answer. In the film you said how fast a thought was, but then he was talking about how our reaction times can be quicker than a conscious thought. So is the speed of an unconscious thought faster than what you were talking about or is our body capable of reacting before it consults with our brain?

Hi Eve

For this question, there are many different factors that need to be taken into account.

At the most fundamental level, there’s the speed at which information, signals, can move through the brain. This is set by neural conduction speeds; the rate at which the electrochemical change, the action potential, in the membrane of a neuron can move. This is how our brain does basically anything and everything, passing these signals from one neuron to another, in incredibly complex ways and patterns.

In truth, the speed at which neurons can conduct these signals is dependant on the type of neuron we’re looking at. For instance, the nerves responsible for proprioception (our sense of the position and movement of our body) are impressively rapid, conducting signals at up to 120 metres per second.

By contrast, certain neurons responsible for conducting pain signals are very slow, topping out at 2 metres per second, maximum. Hence you get those dull ‘slow’ aches at times.

So if we say that, on average, the speed of signals through neurons is around 60 metres per second, it’s still orders of magnitude slower than electrical signals, which move along at a significant fraction of lightspeed. Even faster if we’re talking about fibre optic cable.

This may make neural signals seem slow, but it’s all relative. It’s slower than lightspeed or electrical information conductance, sure. But 60 metres a second is still impressively fast when you consider the average brain is about 16 centimetres at it’s longest point. So neuronal signals can bounce from once side of the brain to the other about 400 times in a single second.

However, the question isn’t ‘how fast do neural signals move?’ It’s whether unconscious thought is faster than conscious thought.

At this point, we’re wandering into philosophical territory. For instance, it could be argued, quite reasonably, that ‘unconscious thought’ is an oxymoron. Because if it’s a thought, then logically it’s a conscious process.

And then we have the issue of what counts as a ‘thought’, per se. This is a constant problem in the worlds of neuroscience, psychology, and related areas. Where exactly does a thought begin and end, and what is involved while it’s happening?

You can watch the Rapid Motion Through Space documentary here and Dean’s new book is out now.

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Dr Dean Burnett is a neuroscientist and best selling author of such books as The Idiot Brain and The Happy Brain. His former column Brain Flapping for The Guardian (now Brain Yapping here on the CSN) was the most popular blog on their platform with millions of readers worldwide. He is a former tutor and lecturer for the Cardiff University Centre for Medical Education and is currently an honorary research associate at Cardiff Psychology School and Visiting Industry Fellow at Birmingham City University.  He is @garwboy on Twitter.

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