Hey Lukeprog, thanks for your article.
I take it you have read the new book "Pleasures of the Brain" by Kringelbach & Berridge? I've got the book here but haven't yet had the time/urge to read it bookend to bookend. From what I've glimpsed while superficially thumbing through it however, it's basically your article in book-format. Although I believe I remember that they also give "learning" the same attention as they give to liking and wanting, as one of your last quotations hints at.
It's quite a fascinating thought, that the "virtue" of curiosity which some people display is simply because they get a major kick out of learning new things - as I suspect most people here do.
Anyway, I've never quite bought the experience machine argument for two reasons:
1) As we probably all know: what people say they WOULD DO is next to worthless. Look at the hypnotic pull of World of Warcraft. It's easy to resist for me, but there may very well be possible virtual realities, that strike my tastes in such an irresistible manner that my willpower will be powerless and I'd prefer the virtual reality over this one. I may feel quite guilty about it, but it may be so heroin-like and/or pleasurable, that there is simply no escape for me. It's phenomenally easy to bullshit ourselves into thinking we would do what other people and what we ourselves would expect from us, but realistically speaking we're all suckers for temptation instead of kings of willpower. I'd say that if the experience machine existed and was easily obtainable, then our streets would be deserted.
2) For the sake of argument let's assume purely on speculation, that the human ability of imagination has brought with it the rise of a kind of psychological fail-safe against losing oneself in pleasurable daydreams - since the ability to vividly imagine things and lose oneself in daydreams may obviously be an evolutionary counter-adaptive feature of the human brain. If we accept this speculative premise, it may be reasonable to expect, that our brain always quickly runs a query about whether the origin of our pleasure has real/tangible or "imaginative" reasons, and makes us value the former more/differently.
(I won't be nit-picky about the words "real" and "imaginary" here, of cause all feelings are caused by neurological and real phenomena. I trust you catch my drift and understand in which way I use these two words here).
The human brain can tell the difference between fiction and non-fiction very well - it would be rather bothersome to mistake an image of a tiger or even our pure imagination for the real deal. And for similar adaptive reasons it seems, we are very aware of whether our hedonic pleasures have tangible or imaginary origins. So when I ask "do you want to experience "imaginary" pleasures for the rest of your existence even though nothing real or tangible will ever be the source of your pleasure" then of cause people will reject it.
We humans can obviously indulge in imaginary pleasures a lot, but we usually all crave at least some "reality-bound" pleasures as well. So asking someone to hook up to the experience machine is like depriving them of a "distinct form" of pleasure that may absolutely depend on being real.
So I think the experience machine thought experiment isn't really telling us, whether or not pleasure is the only thing that people desire. Instead, it may simple be the case, that it is indeed an important precondition for a wide range of pleasure to be based on reality - and being entirely deprived of this reality-correlating pleasure may in a way feel like being deprived of water - horrible. People may be right to reject the experience machine, but that tells us nothing about whether or not pleasure is the only thing they desire. So I think the experience machine is a rather poor argument to make in order to illustrate, that there are other things besides pleasure that people care about - the research you cite however is much clearer and quite unmistakable in this respect.
On another note, I think we're missing the most interesting question here: Indeed, there seem to be other things besides pleasure that people care about... but SHOULD they? Should I ever want something that doesn't make me happy, just because my genes wired me up to value it? Why should I want something if it doesn't make me directly or indirectly happy or satisfied?
Wanting something without necessarily liking it may be an integral part of how my human psychology operates, and one that cannot simply be tinkered with... but in the light of advances in neuroscience and nanobots, maybe I should opt to rewire/redesign myself as a hedonist from the ground up?! Valuing things without liking them is no fun... so can someone here tell me why I should want to care about something that doesn't make me happy in some shape or form?
PS: Sorry for the long comment, I didn't have time for a short one.
Related: Not for the Sake of Happiness (Alone), Value is Fragile, Fake Fake Utility Functions, You cannot be mistaken about (not) wanting to wirehead, Utilons vs. Hedons, Are wireheads happy?
When someone tells me that all human action is motivated by the desire for pleasure, or that we can solve the Friendly AI problem by programming a machine superintelligence to maximize pleasure, I use a two-step argument to persuade them that things are more complicated than that.
First, I present them with a variation on Nozick's experience machine,1 something like this:
Most people say they wouldn't choose the pleasure machine. They begin to realize that even though they usually experience pleasure when they get what they desired, they want more than just pleasure. They also want to visit Costa Rica and have good sex and help their loved ones succeed.
But we can be mistaken when inferring our desires from such intuitions, so I follow this up with some neuroscience.
Wanting and liking
It turns out that the neural pathways for 'wanting' and 'liking' are separate, but overlap quite a bit. This explains why we usually experience pleasure when we get what we want, and thus are tempted to think that all we desire is pleasure. It also explains why we sometimes don't experience pleasure when we get what we want, and why we wouldn't plug in to the pleasure machine.
How do we know this? We now have objective measures of wanting and liking (desire and pleasure), and these processes do not always occur together.
Moreover, these animal liking expressions change in ways analogous to changes in human subjective pleasure. Food is more pleasurable to us when we are hungry, and sweet tastes elicit more liking expressions in rats when they are hungry than when they are full.4 Similarly, both rats and humans respond to intense doses of salt (more concentrated than in seawater) with mouth gapes and other aversive reactions, and humans report subjective displeasure. But if humans or rats are depleted of salt, both humans and rats react instead with liking expressions (lip-licking), and humans report subjective pleasure.5
Luckily, these liking and disliking expressions share a common evolutionary history, and use the same brain structures in rats, primates, and humans. Thus, fMRI scans have uncovered to some degree the neural correlates of pleasure, giving us another objective measure of pleasure.6
As for wanting, research has revealed that dopamine is necessary for wanting but not for liking, and that dopamine largely causes wanting.7
Now we are ready to explain how we know that we do not desire pleasure alone.
First, one can experience pleasure even if dopamine-generating structures have been destroyed or depleted.8 Chocolate milk still tastes just as pleasurable despite the severe reduction of dopamine neurons in patients suffering from Parkinson's disease,9 and the pleasure of amphetamine and cocaine persists throughout the use of dopamine-blocking drugs or dietary-induced dopamine depletion — even while these same treatments do suppress the wanting of amphetamine and cocaine.10
Second, elevation of dopamine causes an increase in wanting, but does not cause an increase in liking (when the goal is obtained). For example, mice with raised dopamine levels work harder and resist distractions more (compared to mice with normal dopamine levels) to obtain sweet food rewards, but they don't exhibit stronger liking reactions when they obtain the rewards.11 In humans, drug-induced dopamine increases correlate well with subjective ratings of 'wanting' to take more of the drug, but not with ratings of 'liking' that drug.12 In these cases, it becomes clear that we want some things besides the pleasure that usually results when we get what we want.
Indeed, it appears that mammals can come to want something that they have never before experienced pleasure when getting. In one study,13 researchers observed the neural correlates of wanting while feeding rats intense doses of salt during their very first time in a state of salt-depletion. That is, the rats had never before experienced intense doses of salt as pleasurable (because they had never been salt-depleted before), and yet they wanted salt the very first time they encountered it in a salt-depleted state.
Commingled signals
But why are liking and wanting so commingled that we might confuse the two, or think that the only thing we desire is pleasure? It may be because the two different signals are literally commingled on the same neurons. Resarchers explain:
Conclusion
In the last decade, neuroscience has confirmed what intuition could only suggest: that we desire more than pleasure. We act not for the sake of pleasure alone. We cannot solve the Friendly AI problem just by programming an AI to maximize pleasure.
Notes
1 Nozick (1974), pp. 44-45.
2 Steiner (1973); Steiner et al (2001).
3 Grill & Berridge (1985); Grill & Norgren (1978).
4 Berridge (2000).
5 Berridge et al. (1984); Schulkin (1991); Tindell et al. (2006).
6 Berridge (2009).
7 Berridge (2007); Robinson & Berridge (2003).
8 Berridge & Robinson (1998); Berridge et al. (1989); Pecina et al. (1997).
9 Sienkiewicz-Jarosz et al. (2005).
10 Brauer et al. (2001); Brauer & de Wit (1997); Leyton (2009); Leyton et al. (2005).
11 Cagniard et al. (2006); Pecina et al. (2003); Tindell et al. (2005); Wyvell & Berridge (2000).
12 Evans et al. (2006); Leyton et al. (2002).
13 Tindell et al. (2009).
13 Aldridge & Berridge (2009). See Smith et al. (2011) for more recent details on commingling.
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