Surveys, Genetics.....and Descartes..

A study from the University of North Carlolina says that survey taking is a genetic trait. They studied twins and determined that there was a 45% influence of genetics on survey taking. The study has been reported in numerous places, here for instance http://bit.ly/cG9E2d .

Is this finding so surprising ? It means that the remaining 55% of “influence” affecting survey taking is unaccounted for or attributed to environmental effects. Biologists know that genetic predispositions account for some behavior, so it is not so surprising that survey taking is influenced by genetics. Of course the study doesn't identify exactly how genetics influence survey taking. We never seem to hear that trait X predisposes people to take or not take surveys. It is a step in the right direction though. It is a step to what I call “Respondent Theory”, that is a theory of why respondents take surveys.

For psychologists interested in the antecedent of behavior there has long been the “nature vs nurture” debate. Genetics vs environment. It is a bit of a false debate though, as it is clear there is complex interactions between the two influences. It isn't just one or the other.

This is where Descartes comes in, sort of. He is probably remembered best for his dictum “I think therefore I am”. He also believed, for reasons which are not wholly clear, that the Pineal gland, a small rice grain sized gland at the base of the brain, was the seat of the human soul. There is still no evidence that the Pineal gland has any metaphysical significance, however there is plenty of evidence for its role in the hormone system of the body.

The Pineal gland is the source of Melatonin, a powerful hormone which regulates the sleep/wake cycle and which is also chemically related to steroids and a neurotransmitter called Serotonin (http://en.wikipedia.org/wiki/Pineal_gland). It is also called the “third eye” because it appears to be sensitive to light, remarkable given it is buried away just above the roof of your mouth. The Pineal glands' production of Melatonin is increased by darkness and inhibited by light. It also receives nervous input from the retinas of the eyes.

Consultant psychiatrist Emad Salib of Peasley Cross Hospital in St Helens, Merseyside, UK believes that the level of Melatonin is somehow related to the incidence of suicide. He performed a study which linked birth in late spring to suicide. Suicide has some seasonality, peaking in months of maximum daylight. Salib thinks that people born April, May and June who were conceived therefore in July, August and September had their brain development influenced by high level of melatonin during important development periods of their brain.

It all sounds a bit far fetched, but remember that up until relatively recently we had no idea that the cause of stomach ulcers were bacteria. 30 years ago saying ulcers were caused by bacteria would have been regarded by the medical profession as fringe lunacy as it was thought that stomach acid was too corrosive to allow for bacterial growth (http://en.wikipedia.org/wiki/Heliobacter_pylori) .

There are other behavior traits which seem to have seasonal influences related to birth month, as show below (this diagram was taken from a New Scientist article on the subject):

So what about survey taking ? If there is a 45% genetic influence maybe there are some other influences that can be detected ? I have always wanted to analyse panel members dates of birth to see if there is any seasonality effect on panel membership or responding. If anyone has a panel and wants to test this I will gladly do the analysis.

What ever the case, it points to the importance of having some form of Respondent Theory. If we know why people do or don't join panels, or do or don't take surveys it should help sort out the biases due to panel membership.

We now know about the 45% genetic influence, presumably mediated by some sort of personality/biological trait, what about the other 55% ? It would be nice to know.....