Lie detection

I was prompted by the article at reference 1 in the Guardian a few weeks ago to do a bit of digging. Do people really think that I am lying if I reply to a question too slowly? So what if they do?

The first part of the story, reference 2, based on work with more than 7,500 young people from the US, the UK and France, is that, other things being equal, people are indeed more likely to think that you are lying if you appear to reply to a question slowly. With the tests involved being constructed so that you have no information about whether someone is telling the truth apart from the telling itself. In mitigation, it also seems to be the case that sometimes people take other factors into account, perhaps the need to delve a long way back into memory for the answer to the question.

The second part of the story, as told for example at reference 3, is that people who are lying do indeed take a bit longer to reply than they might otherwise. Telling the truth is easier, requires less brain power, and comes quicker. Cunning experiments have been devised to simulate everyday lying in an experimental context.

I think that a lot of this work is driven by the fondness for lie detector tests and lie detector machines in the US. Machines which have now gone on from your wet palms to tell tale blips of electricity under your scalp.

This tendency to deduce lie from slow is all part of our learning how to get along in society. We have to get along with other people and this includes knowing when they are lying or otherwise trying to mislead us for some purpose of their own. Perhaps to sell us a second hand motor car which they know to be a bit dodgy. Misleading which goes at least as far back as the chimpanzees. Maybe we come with some of the necessary machinery when we are born, but in any event we spend a good many years working it up, working up the necessary skills with our eyes, ears and brains. Noting that getting along, does not mean that we have to get it right all the time. For the species as a whole, getting it right most of the time is probably good enough, so it does not matter too much if the algorithms involved are a bit rough and ready.

The problem now is that we do want to be right nearly all the time, for example in a court of law, and this tendency to assume that a slow reply is a lie rather overdoes things - and is quite hard to calm down, even though being told to disregard speed does help. It is all too easy to get it wrong.

Which brings me back to murder mysteries on ITV3. What you need is proper physical evidence, not peoples’ stories about what they were up to on the day in question.

References

Reference 1: Answer questions quickly or people may think you are lying, researchers say – Natalie Grover/Guardian – 2021. Tuesday, 16th February. 

Reference 2: Slow lies: Response delays promote perceptions of insincerity - Ziano, I., & Wang, D. - 2021.

Reference 3: Using response time measures to assess ‘guilty knowledge’ - Seymour, T. L., Seifert, C. M., Shafto, M. G., & Mosmann, A. L. – 2000.