Impulse by Dr David Lewis

I recently read Impulse and thoroughly enjoyed it. Upon primary examination, while trying to choose a book to hand in for my school’s speech day as a prize, I was interested by the concept of the book; looking at why we do things without knowing why we do them. At first, it seemed as though it was mostly based on general psychology and so I did not expect to read much hardcore medicine related science, but was still interested nevertheless. I was pleasantly surprised to find that in fact the book was heavily science based and had plenty for me to get my teeth stuck into!

I read it while away on a trekking and volunteering expedition in the Atlas mountains in Morocco with a group, and managed to get them all interested in certain aspects of the book, such as how the length of index finger in comparison to ring finger can be used to find a ratio which is then used to determine the likelihood of the individual partaking in risky behaviour.

Another aspect of the book that I found particularly interesting was the section that discussed how animals can use a subconscious sense of smell to avoid inbreeding within their species. This caused me to do some further reading and I found that this occurs largely in birds, such as penguins. This also helps them to find their mates after a long period of foraging, and allows them to find their habitats after days at sea. The same principle applies with mice. They use the their sense of smell to detect which other mice are closely related to them, due to the genes relating to smell being on the same part of the genome as the genes related to the way the immune system identifies its cells. This produces the concept that if you smell similar, you are likely to be closely related. An experiment was done claiming that mice avoid inbreeding in this way, where a mouse was placed into a cage with its brother. When forced and with no other option, the mice would breed. However, if another, non-related male was introduced, the female would mate with the other male over the brother. Interestingly, if the second male was introduced after the female had fallen pregnant, the female would abort her current pregnancy to mate with the new male; a good mechanism to avoid inbreeding. Dr David Lewis claimed that this concept could be transferred and was proven to be in use among humans, in that we subconsciously find people with similar smells to our own less attractive, which is nature’s of way of preventing incest, using MHC (major histocompatibility complex) genes.

The overall message of the book is that a lot of what we do, or at least think we do, consciously, is in fact down to our genes or factors that we cannot control. This introduces the idea that ‘free will in an illusion.’ This is a dangerous concept, as highlighted in the final chapter of the book, due to the fact that it removes all personal responsibility and makes punishment of criminals significantly more difficult, particularly if it were to be widely recognised that free will is in fact a grand illusion. We would no longer be able to send murderers or psychopaths to prison because they could quite easily blame their subconscious (system I) brain and claim they were not in control of themselves; a dangerous and scary concept in my opinion.