Hockenbury Discovering Psychology 5th txtbk

28 CHAPTER 1 Introduction and Research MethodsCan Ginkgo Biloba Enhance YourMental Abilities?The herbal supplement ginkgo biloba ismarketed as a “cognitive enhancer” thatsupposedly improves memory, alertness,mental focus, and concentration, especiallyin older adults. However, studies of ginkgodon’t support those claims (see DeKosky &others, 2008; Gold & others, 2002; NationalStandard Research Collaboration, 2008). Inreviewing recent placebo-controlled, doubleblindstudies, researchers Peter Canter andEdzard Ernst (2007) flatly concluded, “Wehave found no convincing evidence fromrandomized clinical trials for a robust positiveeffect of ginkgo biloba upon any aspectof cognitive function in healthy young people.”What about normal adults age 75 orolder? The large-scale, randomized, doubleblind“Ginkgo Evaluation of Memory (GEM)Study” found ginkgo to be ineffective in reducingthe development of dementia andAlzheimer's disease in older people(DeKosky & others, 2008).Figure 1.4 The GinkgoBiloba Experimental DesignExperimental group(115 participants)Session 1:Test of memory andother cognitive abilitiesGinkgo biloba6 weeks(independent variable)Session 2:Test of memory andcognitive abilities(Dependent variable)DebriefingParticipants:230 adults, age 60+Random assignmentto conditionsData analyzed andgroups comparedResults reportedAlthough it is completely inactive, a placebo can producevery real effects. A placebo effect is any change attributedto the person’s beliefs and expectations ratherthan an actual drug, treatment, or procedure. Also calledexpectancy effect, the potential influence of placebo effectshould not be underestimated. For example, in one study,participants exposed to placebo poison ivy displayed realand painful responses: outbreaks of skin rashes (see Crum& Langer, 2007).In a typical therapeutic effectiveness experiment, participantsare told that they have a 50–50 chance of receivingthe actual versus the placebo treatment. For example, psychologistPaul Solomon and his colleagues (2002) used aplacebo control group to test whether an herb calledginkgo biloba improves memory, concentration, and mentalfocus in older adults. Participants in the experimental group took the manufacturer’srecommended daily dosage of ginkgo biloba for six weeks, while those inthe placebo control group took an identical dosage of placebo capsules. Memoryand other cognitive abilities were assessed at the beginning and end of the six-weekstudy, as shown in the experimental design in Figure 1.4.Placebo control group(115 participants)Session 1:Test of memory andother cognitive abilitiesPlacebo ginkgo biloba6 weeks(fake independentvariable)Session 2:Test of memory andcognitive abilities(Dependent variable)DebriefingThe participants in the ginkgo study were randomly assigned to thedifferent conditions. Random assignment means that all the participantshave an equal chance of being assigned to any of the experimental groupsor conditions. Random assignment helps ensure that any potential differencesamong the participants are spread out evenly across all experimentalconditions. Random assignment also helps minimize the possibility ofbias because the same rule or criteria is used to assign all participants tothe different experimental groups.Using a double-blind technique is another experimentalcontrol in therapeutic effectiveness studies. This means thatboth the participants and the researchers interacting withthem are blind or unaware of the treatment or condition towhich the participants have been assigned. For example, inthe ginkgo biloba study, the researchers who interacted withthe participants did not know which participants receivedthe real or fake ginkgo biloba. The researchers who didknow the group assignments did not interact with or evaluatethe participants. In contrast, a single-blind study is one inwhich the researchers, but not the subjects, are aware of criticalinformation.Using a double-blind technique helps guard against thepossibility that the researcher inadvertently becomes an extraneousor confounding variable in the study. This can happenwhen a researcher, without realizing it, displays demandcharacteristics. These are subtle cues or signals that can biasthe outcome of the study by communicating the behavior orresponse that is expected of the participants. A behavior assubtle as the researcher slightly smiling or frowning whendealing with some participants, but not others, could bias theoutcome of a study.Can you predict the results of the ginkgo biloba experiment?At the end of the six-week study, the test scores of both groups rose. However,there were no significant differences between the improvement in theginkgo biloba and placebo groups. So why did both groups improve? The researchersconcluded that it was probably due to practice effect. The participants’experience with the tests—the practice they got by simply taking themental ability tests twice—was the most likely reason that test scores improvedin both groups.