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There's a widely-held belief [example] that a rat will starve itself to death if given a lever to press that will stimulate some "pleasure center" via electrodes implanted in its brain. Supposedly, the rat gets so fixated with pressing the lever that it won't interrupt this activity in order to eat, and hence the starvation.

I find it hard to believe that any rats have actually done this, so I looked into it a bit.

I found references to an experiment performed by James Olds and Peter Milner in 1954. Their rats spent lots of time pressing their levers, certainly. But they didn't starve to death; they were removed from the experimental apparatus for fear that they might, which is not quite the same thing, and is somewhat inconclusive.

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    I suspect there is nothing more to add here; you've already got the answer. You found the original source, and people are slightly modifying it in the retelling as they often do. What evidence could we give to satisfy you this was the case? – Oddthinking Jan 13 at 1:25
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    Note that any experiment that intentionally (and successfully) sought to prove this assertion would be judged inhumane and therefore would be forbidden by modern ethical standards for animal experiments. – Daniel R Hicks Jan 13 at 3:19
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    @Daniel R Hicks at least I hope so – Alchimista Jan 13 at 12:35
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    @stijn - But an experiment whose sole purpose was to cause rats to starve themselves to death with no "redeeming social value" is highly questionable. – Daniel R Hicks Jan 13 at 18:09
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    @DanielRHicks certainly questionable yes. Still interesting though, as similar behaviour can be witnessed in the worst drug addicts and research might (or might not) provide insight as to why people go there.. – stijn Jan 13 at 19:27
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A version of this claim is present on Wikipedia:

Experiments have shown rats will forgo food to the point of starvation in order to work for brain stimulation or intravenous cocaine when both food and stimulation are offered concurrently for a limited time each day.

Notice "Experiments" plural. The sources apparently are:

Routtenberg & Lindy (1965):

10 rats with electrodes aimed at medial forebrain bundle-posterior hypothalamus (MFB) ... All septal Ss and 4 hypothalamic Ss maintained their weight on this regimen. The other 6 hypothalamic Ss essentially ignored food, spending most of the session self-stimulating, and "self-starved." Self-starving Ss had their electrodes extensively in MFB while surviving hypothalamic Ss had their electrodes in more lateral areas.

Bozarth & Wise (1985):

Laboratory rats were given unlimited access to intravenous cocaine hydrochloride or heroin hydrochloride. ... The mortality rate for 30 days of continuous testing was 36% for animals self-administering heroin and 90% for those self-administering cocaine.

As noted in other experiments, particular conditions are needed to induce such self-starvation in rats.

By the way, it's actually much easier to get a rat to self-starve: Just give them an activity wheel.

A large number of experiments were run in the 1950s and early 1960s to test this theory, as reviewed in Bolles’ influential 1967 book, Theory of Motivation. Many of these experiments measured rates of running as a function of various kinds of food deprivation schedules and, when the experiments were reported, the authors noted—often only in a footnote—that a surprisingly large proportion of rats died in the course of the experiment.

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    Boredom kills, even rats. But any school pupil could tell you that. – Benjol Jan 21 at 13:26
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Starve maybe, die of thirst almost certainly.

You are correct, the experiments they are referring to are the series of experiments by James Olds and Peter Milner in the 1950's 60's and 70's that first discovered the pleasure center in The brain and indeed quite possibly the pioneering experiments in behavioral neuroscience.

In specifically this experiment in 197 which was one of the later ones set up to test if the rats were making a choice based on competing stimuli (food, water, mates, pain, pleasure). Remember these are the foundation studies for all of neuroscience that actually begin to show how the brain worked. This particular study set up basically the simplest maze ever (literally a single T) with the trigger for the pleasure electrode in one direction and a series of other things in the other, both visible from the other in a direct line. They could not reach both at the same time but they could always walk from one to the other. Incidentally his is also the one that forced the rats to cross and stand on an electrified grid inducing pain to push the lever.

To be clear rodents and small mammals in general begin to starve quickly, but die of thirst in an absurdly short amount of time. It takes about a week or two for a rat to starve, only a day or two to die of dehydration^. The rats were found to ignore food and water even when seriously deprived of both, seriously deprived in this case meaning more than 24 hours without food and water (both is important for many rodents the bulk of fluid intake is from food) as long as they had to choose between drinking/eating and electrical stimulation. More importantly no deviation from this pattern was observed no matter how deprived the animals were. Even when the current was removed the rats instead simply laid down were they were and went to sleep rather than seeking easily available food or water. The animals were really in no risk of starvation but were in serious risk of death by dehydration, this is the equivalent of a human going 5-7 days without water, and they still would not stop pushing the lever to get to water that was literally a few feet away.

For ethical reason the animals were eventually fed and watered because the conclusion was they would continue to prioritize stimulation until they died. For similar ethical reasons these experiments were never carried to this end, as it really would not have yielded useful information. Another likely consideration was the surgery was not easy, the whole discovery of the pleasure center of the brain started because hitting a specific portion of a rate brain with the wire was difficult and they hit the wrong spot, so killing the rats would be pointlessly wasteful as well.

Were the animals allowed to die, no, but scientist had and still have every reason to believe they would die if the experiment continued, and they reported as such. You don't have to kill an animal to reasonably believe it will die. The Rats were seriously deprived and still ignored food and water, the conclusions was a certain as reasonable ethics would allow. The rats showed a disturbing lack of interest in other stimulus in general once they acclimated to the pleasure electrode. From modern studies we know the brain becomes increasingly resistant to all stimulus when it becomes acclimated to a super stimulus. The brain basically develops higher pleasure and pain thresholds.

because link stability is an issue the experiment is

Kornblith, C., & Olds, J. (1968). T-maze learning with one trial per day using brain stimulation reinforcement. Journal of Comparative and Physiological Psychology, 66(2), 488-491.

Other linked studies

https://psycnet.apa.org/record/1955-06866-001

https://psycnet.apa.org/record/1957-07373-001

^Mammals in general are very inefficient with water. Mammals deprived of both food and water dehydrate even faster as the bulk of our water intake is in our food.

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    Welcome to Skeptics! This doesn't answer the question - the OP explained that he knew about the Olds and Milner experiments, and he knew the rats weren't permitted to starve. This just repeats that fact. – Oddthinking Jan 22 at 23:14
  • The OP makes it seem like the conclusion they would starve was not well founded, I tired to emphasise why it was and still is very well founded. – John Jan 22 at 23:23
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    I don't think you have. You have explained why the experiment wasn't allowed to proceed, but not that the unperformed experiment would necessarily have the expected conclusion, which is surely the question here. – Oddthinking Jan 22 at 23:34
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    @John I think the edits you made really improve the quality of your answer and draw attention to the reason why the scientists claim that the rats would have starved although none of them actually did. It could be further improved, though, if you quoted vital information like "no deviation from this pattern was observed no matter how deprived the animals were" directly from the study. As it is, we cannot know how much of your answer was quoted and how much you recalled, rewrote or drew your own conclusions. – Elmy Jan 25 at 10:39

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