This study addresses the influence of energy drinks on concentration, examining in particular the impact of their stimulating ingredients (physiological effect) and product label (label/placebo effect) on objectively measured and perceived concentration. A 3 x 3 (beverage x product label) – cross-factorial between-subjects design was applied. 364 students sampled a beverage, evaluated their perceived concentration at different points in time and completed a standardized concentration test after a latency of 30 minutes. While the beverage itself had neither an effect on perceived concentration nor on the concentration test results, perceived concentration was influenced by the product label. The relation between the product label and perceived concentration was partly mediated by expectations, which in turn were conditionally moderated by the global belief in the efficacy of energy drinks.
Die vorliegende Studie befasst sich mit dem Effekt von Energy Drinks auf die Konzentrationsfähigkeit, und untersucht dabei insbesondere den Einfluss der Inhaltsstoffe sowie des Produktlabels auf das subjektive Konzentrationsempfinden sowie die objektiv gemessene Konzentrationsleistung. Dabei wurde ein 3 x 3 (Getränk x Produktlabel) –cross-faktorielles between-subjects Design angewandt. 364 Studierenden testeten das Getränk, bewerteten ihr Konzentrationsempfinden und nahmen nach 30 Minuten an einem Konzentrationstest teil. Während das Getränk selbst weder einen Effekt auf das Konzentrationsempfinden noch auf die Konzentrationsleistung aufwies, beeinflusste das Produktlabel das Konzentrationsempfinden. Dieser Zusammenhang wurde durch Erwartungen mediiert, welche wiederum bedingt durch den Glauben an die Wirkung von Energy Drinks moderiert wurden.
The Label can give (imaginary) Wings: The Placebo Effect of Energy Drinks
When consumers are unsure about the quality of a product, merely the label can suffice for the consumer to reach an overall judgment of the product. Thus, consumers do not only rely on objective features to evaluate product quality, but are also influenced by extrinsic and intrinsic product cues, such as the brand (Allison & Uhl, 1964), the price (Rao & Monroe, 1989), the country-of-origin (Lee & Lou, 1995/96) and the packaging (Barth, 2006). Marketing often makes use of this by purposely communicating certain product attributes, e.g. special product designs.
A similar effect has been found in medical science, an entirely different field. In some cases just the pill itself evokes analgesia, even though it does not contain any effective substances, simply because the patient learned that pills help. The stimulus, as extrinsic cue, alone suffices to provoke a certain response. This is known as the placebo effect, which can contribute up to 40% of the success of medical therapies (Hucklenbroich & Bodderas, 2007).
In spite of its original medical understanding this effect can be transferred to non-medical effects (Borsook & Becerra, 2005). Shiv, Carmon and Ariely (2005a) transferred for the first time the placebo effect to the marketing domain. They found a negative placebo effect of an energy drink evoked by a price reduction and a positive effect provoked by a strong advertising claim. Subject´s cognitive performance enhanced merely through attributed product performance.
The finding of a placebo effect in the marketing domain and the mechanisms it involves as well as the proposed beneficial effects of energy drinks are the focus of this study. It is examined to what extent the beverage itself and the product label influence objectively tested and self-reported perceived concentration. Thus, Red Bull as the market leader is tested for its influence on concentration against a me-too product and a placebo. Further, it was investigated if expectations and a global belief in the efficacy of energy drinks influence this relation.
Energy Drinks as stimulant Drinks
Looking at the food market the trend of an increasing supply of functional food can be observed. Energy drinks belong to this category, as their stimulating ingredients promise to favorably affect particular functions of the body (Food Safety Promotion Board [FSPB], 2003). The Food Safety Promotion Board (FSPB) speaks of “stimulant drinks” as “beverages, which typically contain caffeine, taurine and vitamin(s) and may contain an energy source […], marketed for the specific purpose of providing real or perceived enhanced physiological and/or performance effects.” (FSPB, 2003, p. 3). The definition points out two main aspects: Energy drinks contain stimulating ingredients, of which the main ones are caffeine, and high amounts of taurine and glucuronolactone (Kim, 2003), and they induce certain positive effects in the body. Taurine is an amino acid, which has many different putative physiological functions (FSPB, 2003). Glucuronolactone is a naturally occurring metabolite formed from glucose. Administered orally, both substances are rapidly absorbed and metabolized and are supposed to detoxify the body. There is no or little information available about the effects of high doses as found in energy drinks, as well as about interactive effects between the substances (European Committee, 1999). Energy drinks are to be differed from isotonic drinks, which maintain fluid balance and provide energy for exercise, but do not contain any principal ingredients of energy drinks (FSPB, 2003).
A few studies have investigated the efficacy of energy drinks, mostly Red Bull, controlled by a placebo group particularly probing mental and cognitive effects. In these studies, subjects participated in performance tests and evaluated their mental state before, after and occasionally in-between the tests. It was found that energy drinks had a positive impact on overall mood, whereas a deeper look at this aspect revealed especially a significant influence on energetic arousal (Alford, Cox & Wescott, 2000; Seidl, Peyrl, Nicham & Hauser, 2000; Smit, Cotton, Hughes & Rogers, 2004; Smit & Rogers, 2002). Studies show that energy drinks tend to eliminate decrease of overall mood and especially energetic arousal over time.
A significant impact of energy drinks on memory capacity could not be confirmed (Bichler, Swenson & Harris, 2006; Smit et al., 2004; Smit & Rogers, 2002; Warburton, 2001). Only Alford et al. (2000) reported a positive influence on memory in an immediate recall task. This finding might result from the character of the task, which primarily required a certain level of concentration. This is in line with studies including reaction and concentration tasks.
In simple reaction time tasks, subjects had to press a key in response to the presentation of a target stimulus. The reaction time decreased in the energy drink condition (Smit et al., 2004; Smit & Rogers, 2002). In a more complex reaction task different stimuli were presented to the subject and had to be responded to by a specified rule. The decreased reaction time result of the simple reaction time tasks could be replicated (Alford et al., 2000; Seidl et al., 2000).
Horne (2000) tested students´ driving behavior in a car simulator after the consumption of an energy versus placebo drink during a two-hour drive. While driving, subjects had to respond to audible stimuli occurring randomly every few minutes by pressing a button. The energy drink reduced the reaction time in the period 30 to 60 minutes after consuming the drink.
Another performance dimension is tested by digit-cancellation tests that measure concentration. Two studies confirmed a significant improvement in concentration after the administration of an energy drink (Alford et al., 2000; Seidl et al., 2000). But interestingly Alford et al. (2000) also showed a significant improvement in concentration in the placebo group.
Many authors made the intuitive assumption that caffeine might be the main component responsible for the energy drink´s efficacy (Horne & Reyner, 2000; Smit et al., 2004). However, only Smit & Rogers (2002) provided empirical evidence for this assumption by investigating the ingredients separately and comparing these results to an energy drink containing all ingredients. Studies on caffeine are in line with studies on energy drinks in so far as they show increased performances in reaction time, concentration tests and mental mood measurements (Attwood, Higgs & Terry, 2007; Brice & Smith, 2002; Kennedy & Scholey, 2004; Liebermann, Tharion, Shukitt-Hale, Speckman & Tulley, 2002; Smit & Rogers, 2000; Smith, 2002).
Research showed evidence for claims about the beneficial cognitive and mental effects of energy drinks. Thus, the first assumption of this study investigates the impact of energy drinks in contrast to a lemonade (the placebo) on one of the claimed performance dimensions, namely concentration, as this field is of current interest being one of the fastest growing research areas in cognitive psychology (Johnson & Procter, 2004) and because it is measurable on an objectively measured and subjectively perceived level. Hence, the first analysis assumes a positive impact of energy drinks versus a placebo on objectively measured and perceived concentration.
Therefore, a closer look at the construct concentration is essential at this point. For a long time there was no consistent definition of this term. It was often used in connection with the term attention or even used synonymously (Leitner, 2005). Bühner (2001) pointed out that both terms express the same construct but were called “attention” by American and “concentration” by European scientists. However, there still seems to be a difference between these terms since concentration has been widely seen as a special form of attention (Leitner, 2005). Hence, concentration describes the selective and focused form of attention (Johnson & Procter, 2004) and thus people are concentrated, if they focus their attention on a selected stimulus ignoring the surrounding stimuli (Neumann & Simon, 1994).
Concentration can be measured by three test categories: calculation tests (e.g. the K-L-T test), where (memorized) figures have to be added or subtracted, sorting tests (e.g. the KVT test), where cards have to be sorted by a specified rule, and the digit-cancellation tests (e.g. the d2-test), where a specified digit surrounded by other digits has to be cancelled line after line under time pressure (Bühner, 2001; Johnson & Procter, 2004).
Concentration has a quantitative dimension, which describes the speed or reaction time, and a qualitative dimension standing for accuracy. The digit-cancellation d2 test by Brickenkamp (2002) tests concentration for these two dimensions. Because of the high reliability and validity of this test (for a discussion see Brickenkamp, 2002) and because of its practical application, this test was used for the first analysis described above in order to measure the objective level of concentration being tested for both dimensions, speed and accuracy.
Kim (2003) presumed in her conclusion that in addition to the ingredients, the simple fact of drinking an energy drink could compound the chemical´s actual effect. This phenomenon of additional effects is supposed to be elicited through psychological mechanisms in human beings.
Psychological Mechanisms influencing Product Performance
In order to evaluate a product, consumers rely on various information or characteristics of products, both extrinsic and intrinsic. As already mentioned, extrinsic product cues are product-related attributes, such as brand name and price, country-of-origin and packaging. Intrinsic cues are physical attributes of a product, such as the memory capacity of a computer or nutrition ingredients, and are thus specific to the particular product (Lee & Lou, 1995/96). The consumer can evaluate intrinsic cues through experiencing the product, while extrinsic product cues can already be used in pretrial product evaluations.
In line with the definition of extrinsic cues, Pohl (2004) defines “…a specific label is affixed to a stimulus and exerts its distorting influence in subsequent judgement or recall” (Pohl, 2004, p. 327). Different extrinsic cues can thus serve as a label, such as a brand name or country-of-origin (Chiou, 2003; Priilaid, 2006), which are used for evaluating the product quality (Rao, 2005). The assessment of the quality is influenced by the label, independently of the objective quality, which is called the labeling effect (Pohl, 2004). Especially in a situation of uncertainty regarding the product´s quality, the label plays an important role by reducing or even eliminating ambiguity. The label serves as a suggestion and generates expectations so that consumers perceive the product in a certain way (Cardello, Maller, Masor, Dubose & Edelman, 1985).
Whereas the labeling effect just considers extrinsic cues, a similar but different effect also takes the intrinsic cues into account. This is known as the placebo effect, defined as a “genuine psychological or physiological effect, in human or another animal, which is attributable to receiving a substance or undergoing a procedure, but is not due to the inherent powers of that substance or procedure.” (Stewart-Williams & Podd, 2004, p. 326). This means that an effect or a change occurs, even though the stimulus that usually evokes this effect is not involved. The substance responsible for the effect is called the placebo, which has no inherent power to produce the sought or expected effect (Stewart-Williams & Podd, 2004). Applied to the medical field, a pill can serve as a placebo and as such e.g. evokes analgesia although active agents are excluded. The placebo response can be any change occurring after administration of the placebo, whereas the placebo effect is the portion of the placebo response (Stewart-Williams, 2004). There are different theories trying to explain the placebo effect.
Literature provides two theories to describe the underlying mechanisms of the placebo effect: Classical conditioning and expectancy theory. These two theories have often been seen as competitors (Stewart-Williams & Podd, 2004). There is no agreement on the dominant theory and thus authors find arguments either in favor of classical conditioning (Voudouris, Peck & Coleman, 1990) or expectancy theory (Kirsch, 1997). Shiv et al. (2005a) refused this view and argued that both theories can be applied simultaneously.
The classical conditioning paradigm can be traced back to a study with dogs by the scientist Pavlov in 1904 (Stewart-Williams & Podd, 2004). A neutral stimulus (bell ringing) was paired with an unconditioned stimulus (administration of food), which lead to an unconditioned response (increased saliva). After pairing the unconditioned stimulus with the neutral stimulus for several times, the neutral stimulus turned into a conditioned stimulus. From this point on, presenting the conditioned stimulus (bell ringing) sufficed to release the response (increased saliva), that now turned into a conditioned response.
Applying this approach to the placebo effect, the active ingredient is the unconditioned stimulus and its unlearned effect is the unconditioned response. If the drug is paired with a neutral stimulus, e.g. a pill, a reasonable amount of times, the neutral stimulus will be sufficient to evoke the response, e.g. alleviation of pain. This means that at this point the pill turns into the conditioned stimulus and the alleviation of pain becomes the conditioned response. Within this framework, a placebo is a conditioned stimulus and a placebo effect the conditioned response.
Classical conditioning can be applied to objective placebo effects (as shown for saliva in the example of Pavlov`s dog), and even to subjective effects (Stewart-Williams & Podd, 2004).
Another way to interpret the placebo effect is the expectancy theory. Kirsch (1997) as a representative of this theory states that conditioning only works by forming expectations, which are effected by the given placebo. The expectancy theory indicates that the placebo causes an expectation about the incident of a certain effect within the recipient (Stewart-Williams & Podd, 2004). This expectation then produces the assumed effect. The expectancy theory can account for any effects for which a subject can develop an expectation, and as such it can be applied to any kind of placebo effect (Stewart-Williams, 2004).
The presented theoretical background justifies the assumption, that merely drinking a placebo energy drink can lead to increased concentration. Energy drink´s, in particular Red Bull´s benefits are widely known, so they are attributed with a positive effect on performance. As discussed above classical conditioning as well as expectancy theory can be applied to the placebo effect, on an objective and subjective level. Thus, in the second analysis it is assumed that the product label will have an impact on objectively measured and on perceived concentration. In particular the label of Red Bull, the market leader, will be tested for its influence on concentration against the label of a private label, which contains similar ingredients like Red Bull but does not have its strong brand image, and against the label of a lemonade (the placebo), which does not contain any stimulating ingredients.
In line with theory, expectations influence the placebo effect, which can even be seen as its main influential factor (Kirsch, 1997). Shiv et al. (2005a) gave empirical evidence that expectations greatly influence the placebo effect. In this study, the third assumption investigates whether expectations mediate the effect of the product label on perceived concentration. It is assumed that especially the Red Bull label increases expectations and lead to higher perceived concentration than the label of a lemonade, but also than the one of a private label.
There is a wide range of empirical evidence revealing the influence of external cues on product evaluation, thereby proving the existence of the labeling effect. In one of the most popular studies on the influence of a label on taste-related judgments Allison & Uhl (1964) asked beer drinkers to rate different kinds of beer. In a blind test ratings did not vary amongst the different beers, but when the beers were labeled subjects gave the one they usually prefer higher ratings, these being higher than in the blind test. Subjects could not identify their preferred label on the basis of objective product attributes in a blind test. This finding is supported by another study, where subjects split equally in their preference for either Coke or Pepsi in a blind test (McClure, Tomlin, Cypert, Mantague & Mantague, 2004). However, if the label was added, Coke was preferred. There are many studies about the labeling effect, all showing the same results: Subjects evaluated products according to their label (Levin & Gaeth, 1988; Pohl, Schwarz, Sczesny & Stahlberg, 2003; Wardle & Solomons, 1994; Herz & Clef, 2001).
Beside extrinsic cues packaging is another important cue for product evaluation. Barth (2006) figured out that packaging played a more important role than the wine itself as product evaluations were higher for the bottle than for the carton irrespective of the objective quality of the wine. Not only the type of packaging but also its graphical component can influence beliefs attributed to the product and even purchase intention (Bone & France, 2001). While Bone & France (2001) found the verbal components of packaging in comparison to the graphics more salient, verbal components can also influence purchase behavior (Kiesel & Villas-Boas, 2007).
Cable News Network (2007) reported a recent study conducted by a professor of Stanford University, where children preferred food wrapped in McDonald`s packaging to food in neutral wrappers. As the company´s advertising seemed to be one of the factors explaining this result, another study supports the sole influence of advertising on product evaluation (Hoch & Ha, 1986). If information for product evaluation is ambiguous, subjects used advertising to make their decision. When advertising provided confirming and no or little disconfirming information, subjects subsequently rated the product higher.
The influence of another type of external cue, namely the country-of-origin, is the content of a study by Chiou (2003). Subjects rated digital cameras from Japan better in pretrial expectations as well as in post-trial evaluation than those from Taiwan. This country-of-origin effect also applied to clothes, which were better rated if labeled Italian than those from Taiwan.
Also more complex information about a product influences product evaluation. Klein (1999) gave subjects information in order to manipulate their quality expectations of a camera. This information did indeed show an impact on attribute judgments as well as a change in the post-trial overall product evaluation irrespective of the camera´s actual performance.
The studies showed that different kinds of labels, as extrinsic cues, have an impact on product evaluation. What happens if intrinsic cues come into play? This is the point of a changeover from the subject of the labeling to the placebo effect. It has been questioned whether there is actually a phenomenon like the placebo effect or whether the effect can be just ascribed to methodological and interpretation errors (Stewart-Williams, 2004), e.g. regression to the mean (Ole, 2003). Indeed, there is a wide range of studies providing evidence for the existence of the placebo effect mostly administering caffeine trying to prove the theories mentioned above.
Schneider et al. (2006) administered decaffeinated coffee altering the information about the presence of caffeine. Being told that they received caffeinated coffee, subjects showed increased alertness and a tendency towards improved reaction time.
Flaten & Blumenthal (1999) found empirical evidence for classical conditioning when they figured out that a caffeine-associated stimuli increased physiological and psychological arousal in regular coffee drinkers. In accordance with classical conditioning the administered coffee, as unconditioned stimuli, elicited increased arousal even in the absence of caffeine. The direction of the effect of the caffeine-associated stimuli (decaffeinated coffee) was the same as for caffeine (caffeinated juice) though its strength was weaker for the stimuli than for caffeine.
In a subsequent similar study they investigated the effects of expectations prior to the administration of the drink but found limited support for the expectation theory (Flaten, Aasli & Blumenthal, 2003). Expectations of the effects of coffee and the actual effects of decaffeinated coffee correlated positively. But there was no significant effect on subjective arousal for decaffeinated coffee. The study showed that the caffeine-associated stimuli were able to raise expectations but surprisingly did not lead to the predicted placebo effect. By contrast, Green, Taylor, Elliman & Rhodes (2001) found this effect for glucose. The mere information about the substance increased the level of cognitive performance irrespective of the substance.
Another caffeine study provided support for the assumption that both theories can appear at the same time (Mikalsen, Bertelsen & Flaten, 2001). When subjects thought they were drinking coffee they gave higher estimates for their subjective alertness opposed to ratings in the juice condition. As in the previous study this finding supported classical conditioning as coffee was the conditioned stimuli that led to an increased level of alertness irrespective of the presence of caffeine. However, it was also found that the information on the caffeine content influenced subjective alertness providing support for the expectation theory. Their data suggested that placebo effects were strongest when conditioned and expectancy-based responses acted in union.
Two other studies applied the expectation theory and made participants believe that they were drinking regular coffee, while actually drinking decaffeinated coffee (Fillmore, Mulvihill & Vogel-Sprott, 1994; Fillmore & Vogel-Sprott, 1992). Different groups were told this drink would either enhance or impair their performance in mood and in a psychomotor coordination task. Both studies found that the groups performed in line with the information they had received. Additionally, Fillmore & Vogel-Sprott (1992) asked subjects prior to the treatment to assess how caffeine would affect their motor performance. As subjects predicted quite weak effects, the result of the performance could be attributed to the expectations resulting from the information received as to whether caffeine enhances or impairs motor performance.
Another study indicates the importance of expectations. Oei & Hartley (2005) found increased performance in a detection task only in the group of subjects that expected a positive impact of caffeine on their performance.
Shiv et al. (2005a) conducted a study of special value transferring the placebo effect to the marketing domain. The first experiment investigated the effect of the different prices of an energy drink on a puzzle-solving task. In a variation they drew participants´ attention to their price-efficacy beliefs making some of them realize that these beliefs may not be applicable and thus weakened their response expectancy. In the third experiment they added weak and strong advertising claims. They found that a price reduction led to a negative placebo response, also when response expectancy was weakened. A positive placebo effect was only be revealed in the case of strong a advertising claim. They first documented that non-conscious expectations of the relationship between price and quality could influence consumers in a placebo-like manner.
Impact of the global Belief
In the above study, drawing subjects´ attention to their global price-quality beliefs weakened response expectancies and eliminated the placebo effect. In a revision Shiv, Carmon and Ariely (2005b) redefined their previous framework of the placebo effect and added the component that expectations can be moderated by different factors, e.g. a global belief such as the price- or brand-efficacy belief. For example, dark dots in bourbon vanilla ice-cream are considered dirty in England whereas in Germany they are attributed to high quality. It is obvious that attributed expectations can essentially be influenced by the global belief. Thus, the fourth assumption presumes that the global belief in the efficacy of energy drinks moderates the impact of the energy drink label in comparison to the label of a lemonade on expectations.
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