Hey, sucker

How to identify an extrovert: First, take one lemon. Now, find a flatmate, small child or passerby and invite them to swallow and swallow until their mouth is as dry as it can get. Administer five drops of lemon juice to the volunteer’s extended tongue and have a measuring cup ready to capture the result.

When you taste something citric and juicy, your mouth produces saliva. This is your reticular activating system responding, “flooding” your gob to dilute the strongly flavoured stimulus so it’s less irritating to your mouth tissue.

People produce different amounts of saliva when lemon-challenged.

Some people’s mouths remain as dry as before, while I’ve needed to grab a bucket for others. Importantly, this difference has been tied to the levels of a particular personality trait – extroversion. The more saliva you produce, the more extroverted you are, according to the theory.

I first came across the lemon test in a book of psychology lab demonstrations, and the name that’s associated with it is Hans Eysenck, who developed a theory of personality that owes much to Carl Jung. In 1933, Jung contrasted, in Modern Man in Search of a Soul, a group of men who in “a given situation at first draw back a little as if with an unvoiced ‘no’ and only after that are able to react”, against another group who “in the same situation, come forward with an immediate reaction, apparently confident that their behaviour is obviously right”. Jung popularised the terms introvert and extrovert.

Extroversion, this dimension of sociality and outgoingness, has stood the test of time and, as far as we can predict the future, will always remain a foundational pillar of personality.

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