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Hedonic Impact ("Liking"), Incentive Salience ("Wanting"), and "Food Reward": Why Are We Hungry? Part VI
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September 28, 2011
5:10 am
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Caution: contains SCIENCE!

Now we enter the heretofore-murky waters of liking, wanting, and "food reward".

(Part VI of a series. Go back to , , , , or —or go on to .)

Summary: The Story Thus Far

In previous installments, we’ve established the following:

  • Hunger is not a singular motivation: it is the interaction of several different clinically measurable, provably distinct mental and physical processes.
  • In a properly functioning human animal, likes and wants coincide; satiation is an accurate predictor of satiety; and the combination of hunger…
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September 28, 2011
5:31 am
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Gnoll
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"it’s obviously absurd to say alcoholism is caused by “alcohol reward”—but if we distinguish the hedonic impact of alcohol from the incentive salience of alcohol, suddenly we have a handle by which to grasp the issues and make headway."

Nicely put.

 

I wonder if the various biochemical mechanisms underlying 'incentive salience' can become desensitized over time - such as we see with addicts whose dose/response relationship adapts over time?

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September 28, 2011
6:29 am
Franco
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The first thorough explanation of "reward" in paleo-cycles! And even I got it - almost.

You lost me here:
"For instance, the fact that the satiety response can modify incentive salience does not make satiety part of the reward response."

If satiety does modify the drive to want more food (and it does indeed!) how can it be not part of the reward response?

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September 28, 2011
6:37 am
lynn
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As long as I don't "wake the monster" of insulin, I don't "want" any particular food. I was just on vacation for a week with 8 in-laws who ate everything that is (was) my very favorite foods, hot freshly made apple pie, at the Apple Barn in Gatlinburg,Tenn, red wine,pasta, chocolate, and so forth. I no longer "want" any particular food. I can't be tempted. My brain knows the "monster will wake up". I will be constantly craving and eating those very things, not because I want them but because my insulin resistance is so powerful and my muscles will literally be starving.. I could look upon all those foods last week with apathy.
Living in freedom for me is living with out the driving constant craving. Also living in freedom from aching knees and hips.
I've been doing Paleo since Memorial Day of this year. My leptin levels are probably still not optimum. I never feel satiated. I never did before I started Paleo, lo carb, but neither do I feel hungry. There have been days when I don't eat at all because I don't feel the need to.
If I do feel hungry, I know I have eaten too much protein at a previous meal and I have insulin floating around. So I eat a couple tablespoons of coconut oil, or some egg yolks and go for a long walk.
I think I could live on a stomach tube as long as the monster did not wake up. It is liberating.

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September 28, 2011
7:08 am
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Asclepius:

What seems to happen often is that hedonic impact becomes desensitized over time.  Ironically, the decrease in hedonic impact usually increases incentive salience in order to maintain a similar level of stimulation.

Franco:

"If satiety does modify the drive to want more food (and it does indeed!) how can it be not part of the reward response?"

Response: "If ice on the road makes my car spin out, how can it not be part of my car?"

And if you somehow define the ice as part of your car, you're going to have to explain how and why it's moving independently of your car...in other words, you've just made a simple problem into a bizarrely complicated and abstruse hairball.

Another excellent reason is "because that's how it's defined in the literature".  If you're going to use standard terms, especially if you're also citing the literature, you need to use those terms in the same way the literature uses them.

lynn:

Part of what I'll be talking about as this series wraps up is "What is the source of my hunger?"  In your case, it sounds like your hunger is driven primarily by a satiety malfunction...issues with energy retrieval (as I discussed in Part IV) cause you to become hungry when your blood sugar fluctuates.  This is distinct from reward malfunctions, which tend to cause problems like binge eating, and which I'll discuss further in future installments.

JS

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September 28, 2011
7:23 am
Monte
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Absolute great album. Torche is great.

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September 28, 2011
8:27 am
Franco
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JS,

and maybe that's one of the flaws in the food reward hypothesis as proposed by the supporters.
I thought we agree that a satieting food full of nutritions(sat. fat, protein, micro-nutritions), however rewarding it is will prevent future overeating to a great extent.
By definitions something that modifies something else must be a part of the equation.

And honestly, your analogy doesn't fit very well.
I meant this: Ice on the road makes my car spin out how can it be not influencing my driving performance(reward)?

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September 28, 2011
9:58 am
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Monte:

Aren't they?  I wanted to link "Grenades," which is my favorite song, but there's no video for it.

Franco:

(I wrote a long reply to your comment, whereupon my browser crashed just as I was finishing it.  I'll reconstruct as much of it as I can.)

Since I'm having a great deal of trouble communicating these concepts to you (for which I take responsibility), I'll abandon the analogy and speak directly.  I'll use the example of the satiety response as something that affects reward but is not itself a reward motivation.

First, the effect of a food on the satiety response is not a function of its effect on hedonic impact, or vice versa.  Foods can be rewarding but not satiating, satiating but not rewarding, both, neither, or anything in between.  (To return to the analogy for a moment, the amount of ice on the road is not a function of your driving skill, or vice versa.)  Trying to measure or explain one purely in terms of its effect on the other simply doesn't work, and neither does lumping them together.

Second, read Berridge et.al.  The reward motivations of "hedonic impact" and "incentive salience" are defined in terms of specific biological substrates in the brain.  You can't just redefine them to include other things, like nutrient sensing in the intestine (the satiety response), in order to claim that reward drives everything.  This sort of sloppy thinking and presentation is a big part of what has made our current situation so disputatious.

"I thought we agree that a satieting food full of nutritions(sat. fat, protein, micro-nutritions), however rewarding it is will prevent future overeating to a great extent."

That's because high hedonic impact ("palatability") tends to increase the incentive salience of a food — while satiation and satiety tend to decrease its incentive salience.  If we lump all these things together and call the whole hairball "food reward", we can't possibly make any sense of the situation, and we end up with hypotheses like "eating bland food is THE solution to the obesity problem" because we can't understand that incentive salience is a push-pull between the other factors.

I'm getting ahead of myself here: this will be explained and discussed in depth in future installments.

JS

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September 28, 2011
12:01 pm
Timothy
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I'm starting to see the path around willpower here. If hedonic impact and incentive salience can be modified by experience, then willpower fades to irrelevance. A hungry Muslim in the presence of frying bacon is not tempted, even though the incentive salience might seem overwhelming to an observer with no cultural aversion to pork.

Likewise, I found that I stopped "wanting" Cinnabons when I learned to regard them as poisonous. If you were very hungry, and placed in a room full of fresh-baked treats that you "liked" very much, but knew that the chef had spiked them all with arsenic and cyanide, you wouldn't "want" them at all, would you? Willpower would hardly enter into the equation.

JS, I wonder what you considered controversial about the present essay. It seems fairly bulletproof to me.

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September 28, 2011
2:17 pm
Uncephalized
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"Likewise, I found that I stopped “wanting” Cinnabons when I learned to regard them as poisonous. If you were very hungry, and placed in a room full of fresh-baked treats that you “liked” very much, but knew that the chef had spiked them all with arsenic and cyanide, you wouldn’t “want” them at all, would you? Willpower would hardly enter into the equation."

This is exactly my strategy and it works very well for instilling an aversion to these foods. I quite agree that it makes willpower a non-issue. The interesting thing to me is that I will still have cravings for specific goodies that I personally think of as "favorites" (for instance, the frosted carrot cake at the cafe down the street from my old house), because they are in a different mental category for me than the generalized "baked goods", which I think of as poison.

I use this to my advantage as well. For instance, I can quite easily indulge in the occasional injera (traditional Ethiopian flatbread, if you're not familiar with it) when I go out to eat Ethiopian food with my friends, because I file it in its own category (under "things that are OK to eat with Ethiopian food", which by nature limits my opportunities to eat it). This does not end up making it harder for me to subsequently resist other baked goods and "birdseed" non-foods, because I don't think of them as being the same thing, and the situations where I will eat certain types are highly contextual.

I find it amazing that I am able to so easily "trick" myself with these little mental rules. The brain is really fascinating.

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September 28, 2011
2:33 pm
Daniel
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So it would seem that Big Food knows something about all this.
Correct me if I'm wrong but if they were to intersect increased palatability, ease of access, and constant advertising, wouldn't that create a perfect storm? It would also seem that the crap food they push (drugs) makes it impossible to ever get any food reward. So like greater palatability with a lack of food reward would spiral into a greater incentive salience. Hope I have that right.

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September 28, 2011
3:10 pm
Beth
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The concept of “palatability” can be understood as the hedonic reward of food

I'm not convinced of this. Kurt Harris (in your link) for example says in effect that the hedonic reward of chocolate chip cookies is higher than that for pringles, but he had a hard time ceasing to eat the pringles while he has no trouble with the cookie.

As a practical matter, saying that a food is "highly palatable" seems to mean animals (including humans) eat a lot of it. Saying something is hedonic implies that whatever it is pleasurable -- so, in this example, one would gather that the hedonic reward of the cookie is greater than that of the pringle, yet the palatability runs the other way.

My impression is that "palatability" is like addiction. People who are addicted to something might think they derive pleasure from it, but they really consume whatever because it has twisted their bodies so it is hard and/or painful to stop.

Beth

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September 28, 2011
4:09 pm
Fmgd
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Beth

To me, saying something is "highly palatable" is more or less the same as saying "it feels good" to eat it, which in turn doesn't mean you eat or even crave it all the time, so it fits with the idea of "Hedonic reward".

Using these terms, "incentive salience", in turn, would be the thing making him crave pringles, even though he "likes" (derives "Hedonic pleasure" from) chocolate chips better. Which, according to the view presented that the reward and the incentive affect each other but are not the only things doing so, is not illogical.

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September 28, 2011
4:23 pm
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Timothy:

Willpower doesn't quite fade to irrelevance — but one can certainly require less of it.  The trouble comes when you say "Well, maybe I'll have just one" about something you've done that trick with, and experiencing the hedonic impact suddenly jacks up the incentive salience which you've tricked yourself into no longer feeling.  

I'll tackle these issues in more depth in future installments, but it's good to see people already understanding where things might go.  If I've laid proper definitional groundwork and explained the existing science correctly, my conclusions should seem obvious — even if they conflict with previous presentations of the issue.

Uncephalized:

The brain is indeed fascinating!  Too many people think the forebrain ("executive function", our "rational mind") is in charge of everything; it isn't.  It's a thin layer spread on top of a big, complicated engine of emotion and instinct.  Like I said in Part III:

As anyone who’s tried to learn to play a musical instrument knows, our prefrontal cortex, our “rational mind”, is not fully in charge. All we have to do is put our fingers here, then here, then here…what’s so hard about that? Yet it takes endless hours of practice, because our PFC isn’t even in full control of our fingers—let alone our hunger drives.

Daniel:

You need to add "nutritional incompleteness so as to never produce satiation or satiety" to the list.  Prime rib is absolutely delicious…but there quickly comes a point when you say "I absolutely cannot eat any more."  Cue my point here, which is that a can of Pringles has the same calories as a dozen hard-boiled eggs.

Also, snack foods have huge hedonic impact…but like any drug, the reward you get from consuming more and more diminishes, while your desire for the high stays the same.  As I pointed out last year, obesity is associated with reduced striatal response to palatable food.  

Beth:

First, a passage I quoted earlier from Berridge et.al.

"…evidence suggests that subjective pleasure is but one component of reward, and that rewards may influence behavior even in the absence of being consciously aware of them. Indeed, introspection can actually sometimes lead to confusion about the extent to which rewards are liked, whereas immediate reactions may be more accurate [1]. In the extreme, even unconscious or implicit ‘liking’ reactions to hedonic stimuli can be measured in behavior or physiology without conscious feelings of pleasure (e.g. after a subliminally brief display of a happy facial expression or a very low dose of intravenous cocaine)"

So it's entirely possible for your conscious mind to think you like cookies more than Pringles, but that might not be your brain's actual reaction.

More importantly, though, is the fact that hedonic impact and incentive salience ("wanting") are two distinct and separable phenomena, with different biological substrates.  Clearly, to Dr. Harris, Pringles have greater incentive salience than cookies, despite his rational mind's estimate that the cookies have more hedonic impact.  

That's why I've explained these concepts!  If we present "food reward" as a single, unitary concept, we can't possibly make any sense of this phenomenon.

(And just as I've finished writing this, I see Fmgd has said exactly the same thing.  Good work!)

Fmgd:

That's exactly how I interpret the literature.  I'm glad it makes sense to you.

JS

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September 28, 2011
4:46 pm
JKC
Guest

Loved the intermission. :)

Great series! I am always happy when I see you have a new installment. I also found defining "liking" and "wanting" very thought provoking. I am not sure I see exactly where you are going to go with this, but I look forward to finding out. :)

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September 28, 2011
4:54 pm
Beowulf
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"Incentive salience (“wanting”) is not an intrinsic property of food, or anything else. Unlike our instinctive aversion to spiders, humans have no instinctual knowledge of Pringles, Twizzlers, or Cinnabons. Incentive salience is a learned property."

I've had arguments with adults about what kids will and will not eat too many times, and the above quote really sums it up. Kids are not born wanting hot dogs, mac and cheese, chicken nuggets, ice cream, cookies, and french fries. The same kids raised in a different part of the world may well think snacking on bugs is quite delicious. One family I know had no television, and never makes "kid" meals. The five and seven year old are expected to eat what the adults are eating, and I've seen these two chow down on artichokes, stir-fry, various soups and curries, and lots of other typical "adult" foods over the years.

There are of course individual preferences (someone may not like broccoli no matter how often it's offered), but if you raise kids on healthy stuff they're going to eat most of it.

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September 28, 2011
6:17 pm
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JKC:

Torche is great!  Like I said to Monte, I actually like Grenades better, but there's no video for it.  Here's the song.

Beowulf:

An excellent point!  Kids are not born wanting junk...but they're exquisitely sensitive to their parents' reactions.  They want what Mommy and Daddy like, and they're not fooled when Mommy pretends to like broccoli.  When they see the parents enjoying junk food, they learn that junk food is delicious.

Moral: eat real food and feed your kids what you're eating.  If they don't eat it at first, they'll soon be hungry enough that they'll eat it anyway.

JS

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September 28, 2011
7:03 pm
Daniel
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JS: ok yeah that's what I was getting at. The total lack of nutrients makes it impossible for the body so say, "all right,we're good". As well as the addictive nature of junk food. But you have said all this before if I'm not mistaken. I do appreciate you putting it into context within this specific series. Kinda ties some things together for me. I have always found that if I've got some random craving or even a specific one that I'd rather not indulge, if I eat say, a steak or some eggs, the cravings subside. I think for the most part the longer you can abstain from junk food the better you are even willpower wise. I quit smoking several years ago and it took about one year before I could handle being around it without it challenging my will. Food is pretty different though; smoking you quit forever, food not so much. Another example of all this is this fat aversion bull crap. We get this pounded into our heads for like 40 years or more and I hear ppl say, "fat on my steaks makes me wanna vomit". Seriously? If a caveman heard you say that, he would slap you. And then take your steak. And your woman. Lol sheeple.

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September 28, 2011
9:05 pm
Franco
Guest

So my main mistake is not to stick to the scientific defintion of the terms, right?
I might be thinking forward too much too but I still think it is a mistake of science then, not yours, to not include satiety. After all we know that our intestine has specific sensor-machanism (and I'm not speaking about food volume only now) to report exactly what is going on down there to the brain (where reward may or may not be influenced).

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September 28, 2011
9:13 pm
Franco
Guest

"Daniel:

You need to add “nutritional incompleteness so as to never produce satiation or satiety” to the list. "

That's actually what I was trying to say all along. Well....

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