<p>Stimulants</a> Fail to Stimulate? | The Scientist</p>
<p>"The extent to which individuals are willing to make an effort at cognitive tasks may alter their reaction to psychostimulants, a new study in rats suggests. The work, published today (March 28) in Neuropsychopharmacology, shows that while lackadaisical rats concentrate harder if given amphetamine, the drug makes hard-working rats ease off. The rats’ work ethics also altered their responses to caffeine.</p>
<p>Such studies are important because, in humans, an unwillingness to exert cognitive effort, called recruiting effort impairment by psychologists, can be symptomatic of underlying psychological disorders. “Impairment in recruiting effort shows up in a lot of different illnesses—post-traumatic stress disorder, depression, brain injury, ADHD, that sort of thing,” says Jay Hosking of the University of British Columbia in Vancouver, a lead author of the study."</p>
<p>"The huge difference between the animals—that variability—is fascinating because it gets you thinking: what is the neurochemical difference between a worker and a slacker?” says John Salamone of the University of Connecticut, who was not involved in the study. Hosking and his team used the terms “workers” and “slackers” to describe animals that fell above or below the average willingness to exert mental effort.</p>
<p>When the researchers dosed both types of rats with psychostimulants, they noticed that amphetamine made slackers more motivated to work hard, but had the opposite effect on workers. Caffeine had no effect on slacker rats, but the commonly used stimulant caused worker rats to slack off."</p>
<p>"Although the results might make you think twice before drinking a cup of coffee, it is not yet clear to what extent they can be extrapolated to humans. “If it works the same in humans then it suggests that one cure doesn’t fit all, Hosking said. “You can have the same illness but your individual personality is going to affect how a drug works, or doesn’t work, for you.”</p>