An Alarm Built to Go Off

Start with a distinction that everyday English blurs. People say they are jealous of a friend's new job, and they mean envious. Envy is about something another person has that you want: a job, a house, a talent. It involves two people. Jealousy is about something you have that you fear losing to somebody else, most often a relationship, and it involves three: you, the person you might lose, and the rival.

The difference is not only a matter of vocabulary. When the psychologists W. Gerrod Parrott and Richard Smith asked people in 1993 to describe episodes of each, the accounts came apart in predictable ways. Envy ran to longing, inferiority and resentment. Jealousy ran to fear of loss, suspicion and anger.

Why would a mind contain such a feeling?

The evolutionary account, set out most fully by David Buss in The Dangerous Passion in 2000, treats jealousy as a guarding emotion. In a species where pairs cooperate for years to raise slow-growing children, losing a partner to a rival is costly, and a feeling that notices threats to the pair and moves you to act on them would have been worth having. On this account jealousy is not a malfunction of love. It is part of the equipment.

Whether every detail of that story is right is disputed, and the next lesson takes up the most famous dispute. But one consequence of thinking about jealousy as a guard is useful whatever you decide about its origins.

A guard is an alarm, and alarms are set according to the cost of their mistakes. A smoke detector goes off when you burn toast because a detector that waited for certainty would let houses burn down. When a false alarm is cheap and a missed alarm is catastrophic, the sensible setting is sensitive, and a sensitive alarm is wrong a great deal of the time. If jealousy is built on that logic, it will fire on weak evidence by design: a late reply, a laugh at somebody else's joke, a name mentioned once too often.

Which brings us to the play everyone quotes.

In the third act of Othello, Iago warns his general: O, beware, my lord, of jealousy; it is the green-eyed monster which doth mock the meat it feeds on. It is the most quoted line on the subject in English, and it is spoken by the man who is at that moment manufacturing Othello's jealousy, deliberately and step by step. The evidence Iago supplies is almost nothing: a handkerchief, a conversation he has staged for Othello to overhear, a hint dropped and withdrawn. Othello supplies the rest. Shakespeare's point is not that jealousy is irrational. It is that an alarm built to fire on weak evidence can be operated by anybody who knows where the switch is.

Research that breaks jealousy into parts makes a related distinction. Questionnaire studies separate reactive jealousy, the flash of feeling when a partner really does flirt with somebody, from anxious or suspicious jealousy: rumination, imagined scenes, checking messages, monitoring where someone is. The two behave differently. The reactive kind is not in itself a sign of a worse relationship, and in some studies it goes with stronger love. The suspicious kind goes with insecurity and with lower satisfaction.

So the familiar line that jealousy shows you care is half right. A flash of jealousy at a real provocation can be part of caring about a relationship. The checking, the surveillance and the imagined betrayals are not evidence of love, and they are the half that does the damage.

That half now has software. In 2019 a group of security companies and domestic abuse organisations founded the Coalition Against Stalkerware, to deal with apps secretly installed on a partner's phone to read messages and track location. Iago needed a handkerchief. The modern version needs a download.

The practical conclusion is not that you should feel nothing. It is to treat the alarm as an alarm: a signal to look, not a verdict, and a signal that is wrong often enough that the looking should be honest.