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Book Summary: The Book of Humans: A Brief History of Culture, Sex, War and the Evolution of Us

Author: Adam Rutherford

Substory: Regret

Regret is an explicitly negative emotion: to feel disappointment for the way things could have been, if only you had acted differently in the past; to feel sadness or anxiety at having failed at something, or having made a poor decision. There is a morality naturally built into regret, that you both could have and should have behaved differently. ‘It seemed like a good idea at the time’ – I love that phrase, for capturing the essence of regret, from the short-term and trivial – ‘one more glass of wine is just the thing before I head home’ – to matters of permanence and consequence.

The complexity of conscious thought required for this sense to be felt is rich. You need two aspects of mental time-travel. First, a perception of the past, a recognition that there were multiple options at that time, and an ability to conceive of imaginary outcomes dependent on an alternative version of events. You also need an ability to imagine a different future. Ultimately, the function of regret is not to wallow in your errors, but to learn from them as an expression of free will: ‘Next time, I’ll do it differently, and the benefits will be greater, or at least, less bad.’ We do it all the time. As an emotion, its existence rests on so many very human qualities. And it turns out rats express regret too.

Again, we must be stringently careful not to assume that behaviours in animals that resemble things familiar to us are the same. Violent and coercive sexual intercourse in animals is not rape, though as discussed earlier, in some cases the comparisons are striking, at least in some dolphins and sea otters. Until we can ask an animal what it is feeling and thinking, we have to make do with rigorous scrutiny, and hold ourselves back from assuming that they are feeling what we do in similar situations, especially when what we experience is complex. A well-designed experiment can certainly help though.

Restaurant Row is one of those experiments. Designed by psychologists Adam Steiner and David Redish from the University of Minnesota, it is an octagonal arena with four dining areas in opposite corners. It’s a bit like a food court in a shopping mall, with multiple restaurants serving different food styles. There are four meals available to the rats in Restaurant Row: banana, chocolate, cherry and plain. Rats, like us, really don’t enjoy waiting for food, and each flavour is only made available to a rat after a random-length wait. There’s also a beep, which descends in pitch to indicate how long they have to wait for the food – the higher the initial tone, the longer the wait. Rats enter the arena and are trained to recognise the tone and the associated wait, and the flavour of the reward that follows.

In the experiment, each of the rats is known to have a natural preference for one of the flavours over the other three. The experiment is to show the rat a long delay for the flavour they like the best, but give them the opportunity to switch to another flavour, rather than hold out for their preference. Say you’ve got a cherry-loving rat, and she knows that she has to wait twenty seconds for her favourite flavour. But it’s a long wait, and the rat bails out after fifteen seconds. She cuts her losses in the hope that she will get a banana-flavoured snack in the meantime. But the banana wait turns out to be another twelve seconds, which means that in total she has waited twenty-seven seconds and got some food that she’s just not that into. She gambled by not being patient, and lost. It’s like being hungry in the mall, and you really want some sushi. But you’re impatient, and the queue for the sushi bar is long because sushi takes time to prepare. So you hedge your bets and switch to a pizza because the queue is shorter, only to see a big batch of sushi arrive as soon as you’ve committed to the pizza queue. The sushi sells out. You’re not that into pizza, and you instantly regret that decision.

The rats regret their change of mind too. How can we tell? They look at the flavour they prefer but didn’t get. To say they looked longingly would be crossing the line into anthropomorphic assumption, but they do turn their heads and stare. In some situations, they waited a shorter time to get a less-favoured meal – the pizza was ready quicker, even though you really wanted sushi, but you eat it anyway. What you might experience here is disappointment, rather than regret. When merely disappointed, they didn’t turn their heads.

More importantly though, the next time they’re faced with that same gamble, they wait. They have recognised that an impatient decision was punished, and learnt to play the odds more conservatively.

If this still seems like interpreting a very ratty behaviour as a direct analogue to complex human emotions, Steiner and Redish looked at what was happening in their diners’ brains while they were being subjected to these scenarios. The orbito-frontal cortex (OFC) is an area of our brains where neurons are known to be turned on when we experience regret. Experiments have been done where human volunteers are subjected to gambling choices which have been secretly contrived by scientists. After their bets are made, and lost, they are shown what they could’ve won if they’d made a different choice; thus, the scientists have rigged the experiment so that they can induce regret in the participants. People with damage to this part of the brain don’t experience it, and report no regret in response to negative consequences after poor decisions. You can’t ask a rat to report how it’s feeling. Instead, the rats in Restaurant Row had their OFC monitored for excitement during their meal choices. Specific cells came alive when thinking about each of the flavours, including their favourites. The same cells sparked when they had passed up on their favourite flavour, had a longer wait, and turned back to gaze upon the missed opportunity. Cherry-loving rats were still thinking about cherry when they gambled and got banana.

While this all sounds a bit cute, understanding the neural correlates in rats of complex human emotions has clinical potential. Some psychiatric conditions include an absence of regret or remorse, or feelings that follow, such as anxiety, which normally might contribute to making a different or better decision in the future. Understanding the circuitry that is damaged or misfiring is where we start to fix it.

The fact that a similar brain area is alert when expressing regret in two distantly related mammals might suggest that the mechanism being adopted to feel this emotion is ancient. Rats and us are separated by tens of millions of years of evolution, but this result doesn’t mean that every species between them and us also expresses regret in a similar way – we just don’t know. Other animals need to be tested in similar ways. Until then, if regret is the emotion in us that induces a change in behaviour when faced with the same situation in the future, we can at least be certain that these rats regret.