Khalil is a professional tennis player and is working on his speed. his friend gives him an herbal medicine that he swears will improve his performance. khalil takes the medicine for a few days and finds that he is performing better. later, it is found that the medicine was only sugar and basil leaves. what might explain khalil's improved performance? the testing effect the placebo effect the experimental effect the sugar and basil leaves

The best explanation for Khalil's improved performance when he was taking the herbal medicine is the Placebo Effect. Sugar and basil leaves in the amount that a medicine dose contains would not have any significant effect on Khalil's performance, but the placebo effect can cause someone to see improvements from a placebo (a treatment with no active effect) simply because they expect to see improvements. Since Khalil expected improvements from taking the medicine, he might have perceived improvements from the placebo effect even though the medicine had no real effect.