老鼠乐园

老鼠乐园（Rat Park）是1970年由加拿大西门菲莎大学心理学教授及其同事针对药物成瘾现象进行的动物实验，其成果于1980年发表。
实验内容.
亚历山大提出一个猜想，认为药物本身不导致成瘾，而在实验室里观察到的实验室老鼠对鸦片类药物成瘾现象，是因为这些老鼠的生活环境，而非这些药物本身的成瘾性所致。在2001年，他跟加拿大参议院说早期的研究将老鼠关在笼子哩，并给他们拴上自我注射装置，而这只能说明说「受到严重压力的动物，就像受到严重压力影响的人一般，在可能的状况下，会透过药物纾解压力。」
亚历山大教授想要证明，在实验室观察到的，老鼠对鸦片类的药物产生上瘾现象，是源自于环境造成的压力，而不是药物作用。为了证明他的假设，他建造了一个符合野外老鼠生活环境的实验区，面积 8.8平方公尺，而这比实验室一般所用的笼子还要大上两百倍，且里头有充足的食物可以享用，同时还有球以及转轮等玩具可以玩，还有足够的空间可进行交配和育儿。在食物充足的环境中，他养殖了16到20只的老鼠，让它们自由活动，有正常的社交生活。老鼠先被喂食57天的吗啡，确认成瘾，再被放至实验区。实验区中提供普通的白开水与加了吗啡的水，让老鼠自由饮用。实验的结果看似证明了他的假设，实验显示，在进入老鼠乐园后，这些先前出现吗啡成瘾现象的老鼠，其吗啡水饮用量，大幅下降，在多数情况下，老鼠选择了普通的白开水，他认为这个实验证明了逃避压力是造成药物成瘾的原因之一。
事后亚历山大教授写道说「没有任何我们尝试的方法‧‧‧能在居住于合理环境中的老鼠，呈现任何看起来像是成瘾的行为」；而在此实验和一些后续的实验中，做为控制组、继续被关在笼子里的老鼠所消耗的吗啡远远较多。
《科学》和《自然》这两本主要的期刊拒绝刊登亚历山大等人最初的论文，之后这篇论文出现在《精神药理学》（Psychopharmacology）这本规模较小但主流的期刊上。开始时，这篇论文的刊登并未引起注意，几年后，西门菲莎大学不再提供老鼠乐园实验的经费。
In the 19th century, drug addiction was regarded as a sign of akrasia, immorality, or weakness of the will. However 20th century brain research replaced this moral model with a disease model of addiction, according to which addiction to a drug is a by-product of the chemical structure of the drug itself. According to social psychologist Stanton Peele, the disease model states that "withdrawal, and craving are thought to be properties of particular drugs, and sufficient use of these substances is believed to give the organism no choice but to behave in these stereotypical ways." This view of drug addiction is reflected in the policies of the War on Drugs and in slogans such as "Heroin is so good. Don't even try it once," or "Crack cocaine is instantly addictive."
Scientists adhering to the disease model believe that behavior is "the business of the brain," according to Avram Goldstein, Professor Emeritus of Pharmacology at Stanford University, and a leading researcher into drug addiction. Goldstein writes that the site of action of heroin and all other addictive drugs is a bundle of neurons deep in the brain called the mesolimbic dopaminergic pathway, a reward pathway that mediates feelings of wanting and motivation. Within this pathway, heroin causes dopamine neurons to release dopamine, a neurotransmitter that determines incentive salience and causes the user to want more. Dopamine neurons are normally held in check by inhibitory neurons, but heroin shuts these down, allowing the dopamine neurons to become overstimulated. The brain responds with feelings of euphoria, but the stimulation is excessive, and in order to protect itself against this, the brain adapts by becoming less sensitive to the heroin.
This has two consequences, according to the disease model. First, more heroin is required to produce the high, and at the same time, the reward pathway becomes less sensitive to the effects of endorphins, which regulate the release of dopamine, so that without heroin, there is a persistent feeling of sickness. After repeated intake, the user becomes tolerant and dependent, and undergoes withdrawal symptoms if the heroin supply is terminated. As the feelings of withdrawal worsen, the user loses control, writes Goldstein, and becomes an addict.
Studies of isolated laboratory animals generally support the disease model.
According to Alexander, the disease model makes either of two claims:
Several decades of animal studies have been seen as supporting these claims. Avram Goldstein wrote in 1979: "If a monkey is provided with a lever, which he can press to self-inject heroin, he establishes a regular pattern of heroin use — a true addiction — that takes priority over the normal activities of his life ... Since this behavior is seen in several other animal species (primarily rats), I have to infer that if heroin were easily available to everyone, and if there were no social pressure of any kind to discourage heroin use, a very large number of people would become heroin addicts.
Twenty years later, Goldstein maintains the same position. In a paper delivered to a 1997 U.S. methadone conference, he wrote: "Every addictive drug used by people is also self-administered by rats and monkeys. If we arrange matters so that when an animal presses a lever, it gets a shot of heroin into a vein, that animal will press the lever repeatedly, to the exclusion of other activities (food, sex, etc.); it will become a heroin addict. A rat addicted to heroin is not rebelling against society, is not a victim of socioeconomic circumstances, is not a product of a dysfunctional family, and is not a criminal. The rat's behavior is simply controlled by the action of heroin (actually morphine, to which heroin is converted in the body) on its brain."
Against this, Alexander argues that the main evidence for the belief in drug-induced addiction comes from "the testimonials of some addicted people who believe that exposure to a drug caused them to 'lose control'," and from some "highly technical research on laboratory animals". He argues that this weak evidence has been embellished in the news media to the point where it has acquired the status of an unassailable fact, whereas the great bulk of historical and clinical evidence, he says, runs against it. He writes that, although the use of opiates in the United States and England during the 19th century was greater than it is now, the incidence of dependence and addiction never reached one percent of the population and was declining at the end of the century. In Britain, he writes that heroin has been widely used in medication for coughs, diarrhea, and chronic pain until the present day; in 1972, British doctors prescribed 29 kilograms of heroin to patients, which he writes amounts to millions of doses, yet a 1982 study of the statistics on iatrogenic addiction in the UK showed a "virtual absence" of such addicts. Recent research confirms that many people use heroin regularly for years, for either recreational or medical purposes, without becoming addicted.
影响.
受此实验影响，开始出现使用生活辅导的方式，让成瘾者脱离痛苦的环境，来协助戒瘾。