Nevertheless, overall, scientific studies have confirmed some specific effects on cognition and learning: Caffeine improves the performance of simple, familiar, routine tasks, and it impairs or fails to affect the accomplishment of complex, novel, unpracticed tasks. Perhaps the reason for this difference is that, by conferring extra energy, caffeine causes a person to work more quickly but possibly less carefully.8
This explanation is in line with experiments that show that caffeine can stimulate fast and strong but incorrect reactions. For example, an experienced computer programmer may report that using caffeine makes well-practiced programming assignments easier to complete, while it appears to sometimes interfere with the successful solution of new and very difficult programming problems. Because real-life problems frequently present both sorts of challenges, and the nature and distribution of these challenges will vary as among different subjects performing the same tasks, caffeine should be expected to produce a complex array of sometimes contrary effects. In other words, although in some ways caffeine may give us a beneficial boost in our capacity to perform certain tasks, in others it may induce us to make precipitous, overeager choices, or to “jump the gun,” interfering with the circumspection necessary for accurate decisions. Perhaps a quick trigger finger is good for the artist’s hand, if the testimony of artists, musicians, and writers such as Balzac, Voltaire, Samuel Johnson, Beethoven, and Goethe about caffeine’s importance in their creative lives is to be accepted. However, psychology, which has yet to attain a coherent understanding of creativity, cannot shed much light on caffeine’s effects on the creative process.
In the laboratory it is easy to create experimental tasks, such as one requiring subjects to identify or remember numbers or colors flashing across a screen, in which few if any of the study’s participants will have been previously practiced. In life, however, most significant tasks are repeated and even systematically studied and practiced with the intent of improving performance. In addition, in many work situations, because people choose the jobs they pursue, they will often be performing those tasks for which they have the greatest innate abilities. For these reasons, it is essential, in predicting the effect caffeine will have on a person’s performance of a given task, to take into account not only the features of the task itself, but also to reckon with the competency of the person performing it.
Is programming a computer difficult or easy? Many people would find even basic programming tasks challenging, complex, novel, and creative. Experienced, well-practiced, and talented programmers might find many of these same programming tasks easy, simple, familiar, and routine. Caffeine might therefore affect performances on a simple programming test in opposite ways: The performance of the person who had little competency with programming, either because of lack of specific experience or specific ability, might well be impaired by caffeine. The performance of the person who was eminently competent in programming, either because of extensive experience or specific ability, might well be given a significant boost.
The effects of caffeine on task performance in real life are complicated still further by the fact that life’s tasks are compound in nature, and, even for the same person, certain elements of a task may be challenging and other elements easy, so that caffeine would exert a variable effect on different stages and parts of the task. We can reasonably speculate that, overall, the more competent you are in performing a task, the more caffeine will help you do even better, while the less able you are in coping with a task, the more likely it is that caffeine will fail to affect or even impair your efforts. If this notion turns out to be true, the use of sufficiently large doses of caffeine, by tending to push lower scores lower and higher scores higher, should serve to flatten the bell curve of an IQ test into a sort of flying saucer.
A curious twist to this question is the possibility that caffeine may affect introverted people differently from the way it affects extroverted people. One study concluded that, when posed with challenging mental tasks, such as proofreading or solving mathematical problems, impulsive, extroverted people get a boost in performance from caffeine, while those who describe themselves as less impulsive and more introverted often suffer marked detriments after caffeine ingestion. Another study of caffeine’s differing effects on extroverts and introverts performing both simple and complex tasks came to similar conclusions. The routine or simple task was to pick out a letter each time it occurred on a page of type. The challenging or complex task was to answer word analogies and sentence completion questions from the Graduate Record Examination. This study seemed to confirm that everybody tends to do better the higher the dose, if the task is extremely simple. However, on the complex task, the extroverts’ performance improved in a dose-dependent correlation with caffeine, while the introverts’ performance worsened.
One additional possibility pertaining to competency comes to mind: If caffeine’s impairment of challenging tasks is a result of prompting us to “jump the gun,” perhaps a person can learn to compensate for this sort of overeager “coupling” even when riding high on caffeine, learning to pause in order to perform the necessary evaluation for a correct choice. If this can be done, then a savvy caffeine consumer might find that he can multiply the number of tasks in which caffeine is helpful and the degree to which it is helpful, and reduce the number and degree to which it causes impairment.
Caffeine and Memory
In recent years, in addition to continuing studies of caffeine’s effects on complex mental activities such as reasoning and learning, researchers have paid increasing attention to its effects on short-term memory. Overall, the results show that caffeine improves performance on tasks that require remembering small amounts of information and impairs or leaves unaffected performance on tasks requiring remembering a great deal. An example of a more demanding sort of memory task is a test in which subjects listen to or read long lists of words and are then asked to remember as many as possible. The experimenters note either no effect from caffeine or perhaps even a small impairment. Another way of conceptualizing these effects is provided by the Humphreys-Revelle 9 model, according to which tasks that are primarily dependent on information processing, such as vigilance, simple arithmetic, or reaction time, are improved, because they make relatively small demands on short-term memory, while tasks with a high short-term memory component may be unaffected or adversely affected. Unfortunately, there is much ambiguity in the data that do exist about these effects. When weighing the conclusions of existing research, we would do well to remember a well-designed 1974 memory experiment by researcher V.E.Mitchell and his colleagues, the cautionary results of which were reminiscent of the title of Luigi Pirandello’s play Right You Are, If You Think You Are, because they seem to demonstrate that performance was improved by caffeine when and only when the participants were told that they had ingested the drug.10
Nevertheless, millions of students use caffeine to fuel “all-nighters.” Based on the available scientific evidence, how does this use of caffeine affect studying and test taking? Caffeine helps people to feel less drowsy and less fatigued, be better able to perform some manual or perfunctory tasks, such as typing or calculating, and, under certain circumstances, to be more capable of sustaining rapid thought and to remember more. However, some studies have found that caffeine does not significantly alter numerical reasoning, short-term memory of complex data, or verbal fluency. In other words, caffeine may help you to stay awake, but it won’t necessarily improve your intellectual skills.
Students depending on caffeine to extend their study time should also be aware of its possible adverse effects when taken in large quantities and be prepared for the crash after its stimulating powers subside. As Socrates suggested, the best guide for students is to know themselves: From a couple of Vivarin tablets, the sensitive may experience restlessness, anxiety, nausea, headache, tense muscles, and sleep disturbances, or a subsequent letdown, while others, from a much higher dose, might feel fine.
A recent startling di
scovery by Menachem Segal, professor of neurosciences at the Weizmann Institute in Rehovot, Israel, and an expert on neuromodulators in the brain, suggests that caffeine causes changes to brain cells that are likely to have profoundly beneficial effects on long-term memory.11 In earlier research, Segal discovered that increasing the amount of calcium absorbed by brain cells is one way of improving longterm memory. Because caffeine augments the ability of these cells to metabolize calcium, Segal studied the effects of adding caffeine directly to the hippocampus, an area of the brain that is critical to learning and long-term memory, to test the hypothesis that the calcium levels inside the cells would rise as a result. The outcome of his experiment confirmed this conjecture, proving that caffeine increased the calcium levels in brain cells. But Segal also observed a more astonishing phenomenon: Caffeine caused existing dendritic spines, the branching extensions at the ends of nerve cells that allow them to make synaptic connections with each other, to grow longer and even caused new spines and branches to develop as well. Although no direct experimental data are available on the actual effects, if any, of caffeine on long-term memory,12 neuroscientists have long believed that an improvement in “wiring” does in fact improve both long-term memory and learning. If this connection is demonstrated in future studies, caffeine would be confirmed as the only known substance that can augment brain functions by altering the physical structure of the brain.
Caffeine and Alertness
Few people would ever question that caffeine helps to keep you awake and alert during the day. In 1990 this phenomenon was first systematically investigated under laboratory conditions and quantified using sophisticated measuring techniques: Researcher Zwyghuizen-Doorenbos led a group of scientists who orally administered 250 mg of caffeine at 9 A.M. and 1 P.M. on two successive days. Checking repeatedly for objective parameters of wakefulness and alertness, they determined that caffeine does in fact help keep people awake and alert. More surprisingly, the subjects who had been previously given caffeine continued to demonstrate increased alertness over the placebo group, even on the third day of the experiment, on which a placebo containing no caffeine was administered to all participants. In discussing this study, researcher Jack James concludes that this extended effect is psychological rather than pharmacological, asserting the “development of conditioned alerting responses to certain contextual stimuli that had been associated with caffeine (e.g., the coffee beverage vehicle used to administer the drug) during the previous two days.”13 In ordinary parlance, this means that if you think you are drinking a caffeinated beverage, you may wake up just as if you had actually drunk it simply because you expect that you will.
A broad range of studies from the 1930s through the 1990s have produced conflicting findings about caffeine’s effect on reaction time.14 Some of the apparently contradictory results may be explained in terms of the 1987 findings of researcher J.D. Roache and R.R.Griffiths, who found that reaction times were improved more by a dose of 400 mg of caffeine than by doses of 200 mg or 600 mg.15,16 Inother words, there is no simple, linear relationship between dosage and improvement in reaction time of which we could state, “If some is good, more is better.” Other studies have confirmed that varying amounts of caffeine produced similarly differing effects on reaction time, finding, for example, that in young adults 300 mg of caffeine significantly improved scores, while doses of 600 mg left them unaffected.
As in the debate over the nature and extent of improvements in cognitive performance, there has been some controversy over whether caffeine can improve psychomotor performance only if you are fatigued to begin with or whether it improves such performance even in a well-rested person. Most researchers agree that it is now well established that the beneficial effects of caffeine are found both before and after decrements in performance owing to fatigue. For example, it has been demonstrated that real-life and simulated automobile driving performance levels are improved by caffeine, irrespective of whether the person was tired or well rested to start.17
Alertness, the complex of mental capacities that suffer during sleep loss, was studied by Michael H.Bonnet and colleagues in 1994 when he compared the value of caffeine and naps in helping to sustain performance during two days and nights of sleep loss.18 Previous studies had shown that performance during sleep loss is, not surprisingly, “improved by prophylactic naps as a function of varying nap length.” Bonnet compared the improvement conferred by naps with that realizable with either repeated or single-dose administration of caffeine. As would be expected, the results showed that an eight-hour “nap,” which is to say, a good night’s sleep, did more to improve performance, mood, and alertness than any sort of caffeine regimen and that the benefits lasted longer than the effects of caffeine, which peak and lose effect within six hours. The study also found that naps could be combined effectively with small repetitive doses of caffeine to maintain alertness. Nothing lasts forever, though. Bonnet concludes that neither a nap nor repeated doses of caffeine could preserve performance, mood, and alertness past twenty-four hours. Beyond that, caffeine’s effects in these respects approached those of a placebo.
Is It All an Illusion? The Caffeine Chippie or the Hidden Need for Caffeine
One of the definitions of drugs that produce a physical dependence is that the abrupt cessation of their use will cause people to perform tests poorly and feel listless and generally “blue.” Leading caffeine researcher Jack James advances a theory that a nearly universal yet unacknowledged physical dependence on caffeine may have confounded the results of many studies that purported to show the psychomotor advantages conferred by the drug.19 His argument is plausible: If nearly everyone uses caffeine nearly every day, then when a scientist takes a pool of subjects and administers caffeine to one part of the group and withholds it from the others, those not receiving caffeine will enter varying stages of caffeine withdrawal and therefore will perform more poorly than those who are not suffering from withdrawal. In effect, James is asserting that most people have what among heroin users is called a “chippie,” a lowgrade habit, of which the habituated person is sometimes unaware, that renders them mildly dysphoric and uncomfortable when deprived of the drug. Such heroin users would probably demonstrate better performance if given a small amount of heroin, simply because the heroin would restore them to a normal metabolic balance and remove the impediment of the mild withdrawal syndrome. If James is correct, all the “improvements” worked by caffeine in psychomotor or cognitive performance may simply be artifacts of an unknown caffeine chippie or a hidden need for caffeine that impairs the habitué when he stops using it. The only way to determine if a nearly universal addiction is distorting experimental findings is to make sure that all the subjects in a given study have been weaned off of caffeine for at least a week or two, so that they begin without any taint of addiction.
Java Jitters or Caffeine Conniptions: Caffeine and Anxiety
It may be nothing to worry about, but anxiety, including such symptoms as unwarranted trepidation, apprehension, agitation, turmoil, and uneasiness, is the most common psychological disorder in the United States. In severe cases, it erupts into recurring panic attacks, the symptoms of which include increased heart rate, palpitations, jitters, irritability, perspiration, and rapid breathing. Caffeine is generally recognized by researchers as an anxiogenic substance—that is, one that is productive of anxiety. The pharmacological basis of this effect remains uncertain. One possible contributory mechanism is the process by which caffeine binds to adenosine receptors, interfering with the systems that would otherwise have reduced anxiety. (Binding to benzodiazepine and endorphin receptors have been cited as well, but at ordinary levels of consumption this activity appears too small to be of significance.) Another is that caffeine interferes with the noradrenergic system so as to increase the release of adrenaline.20 Adrenaline, the hormone the adrenal glands excrete in response to excitement, stress, or fear, produces a more rapid and stronger heartbeat and more rapid and deeper breathing, and it can al
so produce anxiety. Some claim that caffeine in combination with emotional distress causes the release of more adrenaline than emotional distress alone, suggesting that even if it cannot cause anxiety, caffeine may exacerbate it.
In 1971 R.Lynn, a leading British researcher, conducted a monumental study of personal traits and practices and physical and psychological disorders, including psychiatric disorders, cigarette smoking, suicide, coronary heart disease, and anxiety. Observing that the peoples of different nations suffered from different levels of anxiety, Lynn hypothesized that, in those countries in which anxiety levels were high, people would tend to consume less caffeine in order to avoid exacerbating their problems with it. His theory was confirmed by the data. In those countries in which caffeine consumption is low, anxiety is relatively higher, and in those in which it is high, anxiety is lower. Several studies have supported Lynn’s conclusion.21 It has been shown that patients with panic disorder have lower caffeine consumption and that panic attacks can be induced even in normal people challenged with high doses of caffeine.22
The World of Caffeine Page 44