The smell of fish boosts our reasoning skills

The nose is an early warning system, urging us to look closer at what we are planning to put in our mouths. But it's not just alerting us to questionable food. Past research using economic games has shown that when we're suspicious of a smell, this emotion can spill into social situations, affecting how trusting we are towards others. Now a new study shows that even without the involvement of other people to trust or distrust, smell can make us suspicious of ideas and concepts – and this additional scrutiny actually helps us to make better judgments.

In the first experiment, 61 student participants were asked to tackle two factual problems where there was no guarantee that either had a right answer. One of the problems: "What country is famous for cuckoo clocks, chocolate, banks, and pocket knives?" did have a true answer, Switzerland, but the other: "How many animals of each kind did Moses take on the Ark?" was a trick question known to be good at catching people out. Indeed, under standard conditions, more than 80 per cent of participants fell for it. But importantly, a subset of participants had been exposed to a smell emanating from fish oil on the underside of the desk – and these participants did much better at the task, with over 40 per cent suspecting that something was … well, fishy, and choosing the "can't say" response option. These participants weren't indiscriminately paranoid – they didn't misidentify the Switzerland question as unanswerable. This shows that rather than the smell replacing one bias with another – trusting with untrusting – the participants' reasoning improved.

Pong eliminates wrong once more in the second experiment, where 91 participants tried to figure out the rule governing a number series – 2-4-6 – by suggesting further numbers to test their hypotheses. In this predicament, it's vital to use some of the six guesses to try and disprove your rule, not merely to confirm it (the actual rule was "any number higher than the last, regardless of odd/evenness"), but people mostly don't – they are too trusting of their initial conclusions (an error known as the confirmation bias). Under normal conditions, only 28 per cent of participants tried even one disproof. But almost half of participants exposed to the fishy smell tried a disproof, leading them to achieve significantly better rates of identifying the true rule.

Smell doesn't just prime us to treat food with suspicion. It generalises to the social sphere, and beyond that to the realm of reasoning, where it can encourage us to treat ideas more sceptically and questioningly, and to check our own assumptions. Nothing to turn up your nose to.

Further reading

Lee, D., Kim, E., & Schwarz, N. (2015). Something smells fishy: Olfactory suspicion cues improve performance on the Moses illusion and Wason rule discovery task Journal of Experimental Social Psychology, 59, 47-50 DOI: 10.1016/j.jesp.2015.03.006