Here’s why kids are so gross

When adults see something that's physically disgusting — like a puddle of vomit or mouldy food — we recoil. This response is thought to be the core feature of the emotion of disgust: it drives us to avoid substances that could be packed with disease-causing pathogens.

Why, though, are children not as grossed-out by things that adults find revolting? "Curiously, and to parents perhaps worryingly, children do not show strong disgust avoidance," note the authors of a recent study published in Brain and Neuroscience Advances.

To explore why this might be, Sameer Alladin at the University of Bristol and colleagues studied 45 children aged between five and thirteen. In the first lab-based task, the children viewed pairs of images on a screen. One was always of something disgusting — faeces, snot, or vomit, while the other in the pair was a neutral image. In the second task, the children were shown a series of images that were all disgusting, followed by a series of all-neutral images (or the other way around).

Throughout, the researchers monitored the direction of the children's gaze — gathering data on what which images they preferred to look at, and which they chose to avoid. They also used electrodes placed over the children's stomachs to monitor their gastric rhythms.

When an adult is disgusted by something, there's a disruption in the normal rhythm of contractions of their stomach, the team notes. These 'sick' feelings, which they term 'proto-nausea', are thought to play an important role in leading us to want to avoid disgusting things.

The researchers' observed that the children did in fact spend less time looking at the disgusting images, compared with the neutral ones. (In the first study, a typical response was to glance at the disgusting image, then focus on the neutral one.) These results suggest that children do seek to avoid gross things, even from the age of five.

However, when the children were looking at what should have been stomach-churning images, the electrode data showed no changes in their stomach rhythms. In other words, there was no sign of the 'gastric disgust' typically observed in adults who are viewing revolting things. Why, then, did they look away?

The team float the idea that this might have been a learned response — the children might have learned from their parents' behaviour and language that certain things are gross, and should therefore be avoided. If this is true, it may be the case that shunning disgusting stuff starts out as a social norm, with the gastric response then developing later.

They do concede, however, that an alternative explanation for their results is that the images they used in the study — which of course had to be suitable for viewing by young children — were gross enough for the kids to want to look away, but not bad enough to induce a stomach reaction. Further research will be needed to explore whether this is what happened.

Still, most parents will have first-hand experience of toddlers, especially, failing to find bodily excreta disgusting. This is especially curious given that, as the researchers note, young children are more vulnerable than adults to getting sick from pathogen-laden material. But, if it takes time for them to first learn from their parents that some things are revolting, and even longer to develop a stomach response, which presumably strengthens these aversions, this could help to explain their interest in things that we find revolting.

Read the paper in full:
Sameer N.B. Alladin, Berry, D., Evgeniya Anisimova, Judson, R., Whittaker, P., & Dalmaijer, E. S. (2024). Children aged 5–13 years show adult-like disgust avoidance, but not proto-nausea. Brain and Neuroscience Advances, 8. https://doi.org/10.1177/23982128241279616

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