Researchers who tested whether ginkgo biloba improves memory and concentration were careful to control changes caused by other influences so they could be confident that the _____ could be attributed to the treatment variable.
A) practice effect
B) main effect
C) expectancy effect
D) placebo effect

Question

Quizplus · Accepted Answer

The researchers were careful to control for other influences so they could confidently attribute the changes to the treatment variable, which is the main effect of ginkgo biloba. The practice effect refers to improvements that result simply from repeated testing, the expectancy effect refers to the influence of participants' expectations on their performance, and the placebo effect refers to improvements that result from the belief that one is receiving an active treatment, even if the treatment is actually inert. None of these effects are relevant to the question of whether ginkgo biloba actually improves memory and concentration.

Researchers Who Tested Whether Ginkgo Biloba Improves Memory and Concentration