Perception changes how you eat

Do you grab more food when someone's watching?
07 April 2020

Interview with 

Claudia Wascher, Anglia Ruskin University


Pots of cooked food


Now here’s some food for thought! Scientists have found that when you’re snacking, you reach for the food more often if you’re with someone else than you would than if you were by yourself. In this study from the University of Tokyo in Royal Society Open Science, people were given plates of crisps, and grabbed more handfuls when another person was there - even though they didn’t necessarily eat more overall. The authors suggest that it might be because you don’t want someone stealing your food - but is that really what’s going on? Phil Sansom got the independent perspective from Anglia Ruskin University behavioural ecologist, Claudia Wascher...

Claudia - They have basically asked humans to eat crisps for them and they have told the participants that it's about a taste experiment, so the participants had to fill in, "Yeah, crisps were crispy and salty and actually tasted good." But indeed the researchers had a completely different study aim. They actually wanted to find out the eating behaviour of the participants if they're tested alone or with other individuals.

Phil - What's actually physically going on when they do this experiment? Do they sit someone down in a room and they give them a little bowl of crisps and then there's someone across the table from them?

Claudia - Yes, they have tested approximately 60 participants and one group was the ones who were tested alone. Another group was tested with a partner, so when they came into the room there was somebody else sitting opposite them. And then they had a third group. They basically had an opaque barrier so they couldn't see the other individual eating crisps, but they could only hear them.

Phil - What kind of crystals were they?

Claudia - I don't think that they say in the paper because obviously they don't want to do product placement. And this actually could be a conflict of interest for the authors if -

Phil - Was this a study sponsored by Pringles? [laughs]

Claudia - Exactly!

Phil - I have to say, it sounds like a fun study to be involved in.

Claudia - Yeah, it's fun. I think the background of all of this is no matter whether it's humans or birds or fish, foraging in groups has benefits for the individual, so it's less likely that they're eaten by a predator. It's more likely that they actually find foods because they have more eyes to look out for food sources, but once the group has found some food sources, of course there's more competition.

Phil - What did they actually find then?

Claudia - So they found that when there were other people in the experiment that participants grabbed pieces of crisps more often, they didn't necessarily eat more crisps. They authors conclude that people must have taken smaller pieces of the crisps.

Phil - Why then would people have taken crisps more often but maybe a little bit less?

Claudia - They are arguing that it's a competitive situation. You find some food and you basically have to hurry up and get as much out of the food source as possible.

Phil - You're worried someone's going to eat your crisps.

Claudia - Exactly. And the authors kind of said that taking smaller pieces more often could be tactical consideration. I think we all can relate to this. Another explanation which I think is worth mentioning is social facilitation. You're more likely to engage in an action if other individuals are engaged in that action too. Think about other animal species. For example, if you forage in the wild and you're given a bag of crisps in front of you, initially you wouldn't know like are they actually safe to eat? So it might be worth to actually watch other individuals eating them and kind of make a decision, "it's safe to eat this."

Phil - So you're saying it might be like a social activity, like you see someone else eating crisps and you say "oh OK, I'll eat more".

Claudia - Exactly. This is also something, they put two strangers into a room with a plate of crisps. This is a bit socially awkward! We are all group living animals. However, when we meet strangers in the first instance, you will want to know are they a friendly person, and engaging in an activity like eating or even mirroring the activity of the other individual, might kind of signal getting to know each other, getting familiar with each other. Yeah. I think it's a quite fun story to do to kind of test what makes humans tick when they eat. And again, it might be a very unconscious thing which we are not quite aware that it's actually happening. And I think it's fun to get to know people a bit more by doing this kind of experience.


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