The thinking behind SSS is that because humans are omnivores, and we must eat a variety of foods to survive, we evolved this mechanism to keep us from sticking doggedly to our favourite food and consequently getting ill, and/or prematurely popping our clogs. Marion Hetheringon, professor of biospychology at the University of Leeds, describes the process nicely: “If I’m eating a food like pasta, it will taste good at the beginning. Then when I’m halfway through it doesn’t taste quite as good – I might add some more sauce to make it taste better, or I might say I’m going to switch to salad now – I’ve had enough of the pasta.” This happens subconsciously. In fact even people with amnesia who not only forget what they’ve just eaten, but have no idea whether they’ve eaten at all, still express SSS. Served repeated, identical meals, they will continue to eat them, but they find them increasingly unpleasant.

One study back in the 1980s found that once people feel satiated from eating red Smarties, if presented with yellow Smarties (which taste and smell identical), they will suddenly get their appetite back. And more recently, Laurent Brondel at the European Centre for Taste Sciences in Dijon observed that simply introducing a condiment can be enough: “I gave subjects some french fries,” he tells me, “and when they didn’t want them any more, I put some ketchup near the french fries and then the subjects started eating them again.” His team did the same with chocolate brownies, and introducing vanilla ice cream led to greater consumption (although, controversially, whipped cream did not). 

“Children tend to show sensory specific satiety quite strongly,” says Hetherington, and therefore forcing them to finish something they don’t want could be detrimental. “If parents are trying to override internal signals, the child will become more used to environmental signals to determine how much they eat, rather than their own internal signals of hunger and satiety.”