It seems like everything can make us addicted these days. Our iPhones. The internet. Oreos. But just because something is pleasurable and causes a relevant reward area of your brain to light up does not mean that it is addictive.

最近，好像所有事物都能让我们上瘾。iPhone、互联网、奥利奥。但是，仅因为一些事物使你感到愉悦，并刺激大脑引起相关反应，这不意味着上瘾。

An addiction is like a compulsion, where you continue performing a behaviour even though it has resulted in negative consequences – like continuing to drink even though it's lost you your driving licence, your job and even your partner. Addiction also involves complex changes in your brain in areas where you process reward and self-control. These changes can result in feelings of craving and withdrawal, where your body has adapted to rely on the drug to feel normal. In some cases, withdrawal can be so severe that your body may actually shut down and you can die if you don't have another hit.

No matter how many Oreos you eat, this will not happen to you.

The idea of food addiction is not a new one, but a study released last week takes this claim to a whole other (and unsubstantiated) level, claiming that Oreos – and especially that all-enticing creamy centre – is as addicting as cocaine.

Unfortunately, the researchers from Connecticut College who ran this study, led by Professor Joseph Schroeder, never actually tested this hypothesis. They used a standard conditioned place-preference test, giving rats either an Oreo or a rice cake on one side of a maze or another and then watched to see where the animals later chose to spend their time. This type of task is typically used to measure associations between a stimulus (like cookies or cocaine) and the environment in which it was experienced, with the idea being that the more pleasurable an experience is, the more likely you will want to repeat it, and thus the more time you will spend in the place where you first received it. Stemming from this logic, as might be expected, the rats preferred the side of the maze（迷宫，迷惑） where they received the Oreo.

Fine, great, we all like Oreos more than rice cakes. No surprise there.

Then the researchers repeated the experiment, but this time they injected rats with a dose of cocaine or morphine（吗啡） on one side and with a neutral saline solution on the other. Once again, as you might anticipate, the rats kept going back to the side where they had received the drugs, hoping for more.

Now here's where it gets sketchy. The researchers measured the amount of time the rats spent in each half of the chamber and claim that because the two groups of mice spent equal amount of time in the Oreo and in the cocaine area, these two stimuli are equally rewarding, or "addicting". However, they never actually compared the cocaine with the cookies! These were two completely separate groups of animals that took part in two different experiments – one testing Oreos with rice cakes and another comparing cocaine and saline（盐湖）. Yes the animals showed similar behaviours in response to the drugs and to the high-fat/high-sugar food, but these things cannot be equated if they are not directly compared.

To be fair, the researchers didn't just rely on behavioural tests, but also measured the amount of chemical activity that was seen in a reward region of the brain, the nucleus accumbens, in response to each of the two vices. Here they report that there was greater evidence of activation in the Oreo-eating rats than in the cocaine-consuming ones. However, again, they haven't directly compared the amount of activity seen within an animal after receiving cocaine and Oreos.

Many previous studies have directly compared cocaine with food rewards and the results are conflicting. One study measured cell firing in the nucleus accumbens in primates directly after receiving a sip of juice or a dose of cocaine. In these animals, there was significantly greater activity in response to the drugs than the juice.

Now, this isn't to say that the idea of "food addiction", particularly to foods high in fat and sugar, is complete nonsense. For over the past 10 years Dr Nicole Avena and others have been conducting elegant experiments where they let rats binge on chocolate pellets and then measure changes in their brain and behaviour. These researchers quite frequently see similar effects in rats that have been gorging on chocolate as those given cocaine. This includes physical changes in the brain (including in that crucial reward centre), as well as behaviours reminiscent of craving and even withdrawal.

The idea that junk foods can create addictive-like tendencies is not new, nor is it wrong. But the claims that this particular study makes are.

As for whether the eating the middle of an Oreo first really is better, well I guess I'll let that one slide.