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Eating Behavior
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Eating BehaviourGeneral exam information
The exam will consist of 6 open-ended questions, some of which have two sub-questions. Each
question will deal with one of the topics discussed in each week (i.e., question 1 will be about
article/lecture information of week 1, question 2 about week 2, etc.). (examples in manual)
1. Acquisition of likes and dislikes
Learning goals: You are able to describe and explain causal factors determining
preferences and aversions for food. You are able to give advice on how to increase and
decrease liking and preferences for specific foods.
1. Innate Preferences
Some tastes are innately aversive for children, so much so that their whole body reacts. But
interestingly (also mentioned in the paper), very young children even if they obviously don't like it, still
display approach behavior towards that food. There is a difference between Preference (the behavior
of “wanting it”) VS Liking (the enjoyment of it being “tasty”). The baby wants to eat but then every
time he gets it, he doesn't like it.
We have an innate preference for sweet, salty and umami. We don’t like bitter or sour.
- These innate preferences bias learning (learning to like something a little sweet is
always easier than learning to like something a little bitter, they help or hinder the
learning process)
- Innate preferences can be overlearned (learning can override them, we learn to like
coffee)
2. Neophobia
The potato is an interesting example of a dietary change campaign. Its very nutritious and easy to
farm because they multiply (high yield). Perfect plant to feed the masses. It was introduced in the
1600s from South America, but Europeans were reluctant to eat it even if there was a famine. This
was because it was an unknown shape and taste, also from an unknown place and different people
(prejudice). But the most important reason why people didn’t want to eat the potato was because it
looked similar to the poisonous nightshade (which is the “plant of witches and the devil” with
hallucinatory properties). It took 2 centuries and famines before people ate the potato, because of a
campaign. In order to make the potato more popular, the French governments and newspapers
informed about the benefits. Louis XVI put potato flowers in buttonholes and Marie Antonette in her
hair. They also put guards around the potato field to encourage people to steal them. And then they
became super popular.
Neophobia means “fear of the unknown”.
For infants, it takes 7-10 times (for vegetables) to increase liking and consumption.
The learning is easier when it matches innate preferences (carrots are easier than green beans) and
the effects can last for months.
This effect is called Mere exposure: just being exposed to the same vegetable more times increases
linking, but it doesn't do the trick just by itself. It's also important how the exposure takes place, it’s not
enough to just look at it, you have to taste it. You can also observe other people eat it, especially
familiar people, it helps to know its safe to eat. The more often exposed children get, the stronger the
effect in the liking.
1
,Difficult to show long-term effects: It's difficult to study whether what kids eat influences what they eat
when they are older. Is what you like now related to what your parents gave you as a child? A study
looks at this retrospectively (what they remember): The more you eat it, the more you like it. But you
can’t know for sure what causes what. It’s not only about what they are given, the kids also demand
certain foods.
So does any exposure increase liking? Or does it depend on how it is presented? When you
see your parents eat it or you get encouraged to eat it in moderation, this predicts liking. But when
your parents become indifferent or when you are being forced, the liking goes down.
It takes exposure to actually start liking the foods that you don’t know. But it’s also interesting to look
at how to make kids start liking things they don’t know, for example unknown foods. One interesting
study reasons that kids will be more likely to try new foods if they look fun or if they are involved in
creating crafty pictures of food (placing it in the shape of a flower, smiley face…). So somehow
engaging them in a positive way.
They carried out this study where they had 3 conditions; in the first (art) condition the kids
were making artistic fruit flowers themselves and really engaged in crafting it (ikea effect: if you do
something yourself, it acquires value) so maybe somehow the kid may become attached to it and like
it more when they eat it. In the second (visual) condition they also do this creative workshop and also
create a flower arrangement but this time instead of with fruits they do them with just paper, but then
they also get to eat those beautifully presented fruits. And in the control condition they also do the
creative workshop but just eat the same amount of fruits from the container. So how much of the fruits
will the kids eat when asked to eat?
When looking at the food intake variable, they distinguish between familiar (apples) and
unfamiliar (startfruit, papaya) foods. In the control condition where they just eat from the container,
they eat less than in the other two groups. Also, the visual group and the art group don’t differ. So if
the kids were actively involved in making the flower display or not didn’t matter. What mattered was if
they were eating from this beautifully presented display. The same pattern appeared with the number
of foods, we see that this manipulation of making foods fun to eat seems to have boosted especially
the intake of the unfamiliar foods. And this is important when thinking of strategies to make kids eat
something healthy. If you make the display of food fun, then kids will eat more. This positive display,
feeling and eating of food is learning,
Learning from Rewards
We use rewards to make kids eat things they don’t like…
How to create/manage exposure? → Rewards
“if you eat your vegetables, you may watch a film afterwards”→reduced
liking of “means” (vegetables) Kids like what they have to eat to get something they like less if
you present it like this.
Study: They had preschoolers come to the lab a week before the experiment and were given different
snacks and asked them to rate them on a scale. They then chose the snacks that were in the middle,
not favorite or worse. And during the first week that they gave them the snack, all the evaluations
were the same for all kinds of snacks. A week later they were taken back to the lab with 3 different
conditions: one where they were put in a room with 2 snacks in the middle of the ranking. And they
said that in order to get the second snack you must first eat the first one. In the temporal condition,
they just told them they had to eat one of the snacks first and then the other. Finally, in the exposure
condition they just ate one snack and then the other. In all conditions they eat one snack first and then
the second one, but in the first condition they are made contingent: they only get the second snack
when they eat the first one.
2
, And what you see is the temporal and exposure condition, nothing changes, the ranking
remains the same. But in the means-end condition (the first snack becomes the means to get the
second snack) you see that the first snack loses in value (higher ranks lower ranking). If you tell
someone you have to do this in order to get that, they don’t like it.
This mechanism is called overjustification: if I need to be rewarded for this stuff, I don’t like it
because it must be crap!
Another reason is that the negative affect generated by forcing someone is being attached to
the food. This negative affect can come from pressure and also reactance (if you tell people what to
do). And this negativity is being linked to the food, so it’s not a very effective strategy.
But there was more research on this trying to understand some conditions under which this type of
rewarding may work. And when there is no negative affect elicited (loving environment and not set
badly) the decrease in liking is not that bad. And also by making them eat the vegetables they get
exposed to them and maybe over time it will become a habit. If it manages to turn into a habit, this
could be a way to achieve this but it must remain a positive atmosphere. Pressure and negativity does
not work.
So what should you do then? Another study looked at kids in 4 different conditions with the same food
reward (an apple): The first condition looked at what the kid wanted to accomplish (finishing the
drawing, playing with this without breaking it) and at the time they accomplished it, they got the
reward, the apple was the reward. The second condition they randomly came up to the child and gave
them the apple. Another condition was non-social, where they told the child they will find an apple in
their locker 2 times a day, without social interaction. In the final control condition they just
administered the apple during usual snack time as usually happens in kindergarten.
After the follow-up, in the control condition nothing happened: they just ate the apple but the
liking/preference of the apple didn't change. In the non-social condition it goes up a little but then it
goes down again with no lasting effect. Where something changes is in the reward condition and in
the non-contingent attention. You would think that reward would add something special, but this study
suggests that it’s basically the positive attention you give a child what adds value to the object.
(Regarding the non-social condition, why is there no mere exposure effect? If they have been
exposed several times you should see an increase in liking. Interestingly, this actually speaks against
it for some reason.) So, the takeaway is positive social attention.It’s really about positivity, it needs
to carry value. In learning, if you want to increase the value of something neutral, you have to pair it
with something positive.
Instead of saying “if you finish your broccoli you may use the iPad” we should say “if you finish
this bag of chips you may use the iPad”. Or instead of “your report was awesome, here are some
chocolates!” we should say “your report was awesome, here are some carrots!”. But, the vegetable
will be less strong just because of our innate preferences, the chocolate will always be a more potent
reward compared to broccoli. The learning will be faster with the chocolate.
Learning from post-ingestive consequences
The strongest learning mechanism in acquiring dislikes is the negative consequences of ingestion. It
is only with post-ingestion signals like nausea/vomiting which have a strong effect on preference and
liking, not with other symptoms like pain or fever. It is very fast learning, a single pairing is enough,
can persist for decades and has a very strong effect on intake.
There are also positive consequences of ingestion. Normal satiety or feeling full can increase
preference and liking. The learning mechanism is very subtle and slower, and has a small effect on
preference, but it is there. It works against vegetables, because they are not very filling and lose out
on that post-ingestive consequence learning boost.
Learning by association
3
, ● Flavor-flavor association: broccoli with tasty cheese sauce may enhance liking of
broccoli (but the results are inconsistent, sometimes it may make you only want to eat
broccoli if it comes with the cheese sauce since it’s what gives the value to the
broccoli) (example of evaluative conditioning, mentioned in the reading)
● Social associations: especially for young children, modeling by parents works if they
see them eating vegetables. When they grow older, parents become more unimportant
and people start to look at their peers who have a strong influence. Also influencers. (It
is unclear whether social modeling has an effect on preference (buying it) or liking
(enjoying it). If the cool kids eat bananas, I may eat bananas but I may not like it. If you
want to have a real behavioral change, changing the preference is not enough,
changing liking makes it sustainable.
● Contextual associations: cultural context enhances availability/exposure but there is
also a difference in reactions: being given a bad candy but with a positive reaction
when you eat it. Can be strong enough to acquire liking of innately aversive foods
(coffee, chilli). Kids learn to like the pain of spicy food through social facilitation, people
give it to you, smile, encourage and make it a positive experience. Cultural context can
be very strong.
A note on Pavlovian (classical) conditioning
(you don’t have to understand every sentence in the article, it’s about reading it a couple times and
discussing it)
In the article, when they talk about food they don’t
mean the food the dog is eating, the question in
the article is: How does something neutral like
plain pasta acquire taste/liking?
You are the dog. The neutral stimulus (the bell) is
the food: the plain pasta (there is no response).
We want to understand how something that has
no response turns into something really tasty. The
unconditioned stimulus that is by itself potent
(elicits a response), it could be the smile of your
mother or a lover which makes you feel good. In
the conditioning phase, there is a plain bowl of
pasta (food) + smiles of the person you love
(positive peer response), (NS + US), repeated
several times and at some point you like the plain
pasta. This is the idea that the stimulus of this
person you love that gave you a positive signal, has been injected into the pasta and makes it
meaningful. It is attached to this positive value (like childhood memory foods that don’t have value in
themselves). The food doesn’t have the value unless it’s like super sweet or tasty.
(liking does NOT equal preference).
Disgust
Disgust is a basic emotion (one of the 6 universal emotions). It has a very distinct physiology: nausea,
wrinkled nose (the idea behind this is to close off smell). The experience is that of revulsion, and
avoidance. There are 3 distinct appraisals:
1. Fear of oral incorporation (fear of something entering your body)
One of the things that make something disgusting is the texture, unexpected or unfamiliar
textures produce disgust. Eating marzipan when you think it’s cheese creates a disgusted
expression on your face. The negative reaction when they get marzipan is really intense but it
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