In an Experiment Treating Spider Phobia, Half of the Participants

Multiple Choice

In an experiment treating spider phobia, half of the participants get eight hours of cognitive-behavioral treatment. The other half get eight hours of attention from a therapist but no active treatment. Both groups report a statistically significant reduction in their fear of spiders. This is evidence that

A) cognitive-behavioral therapy has no effect.
B) the placebo effect can be significant.
C) participants' expectations have no effect.
D) control groups are a waste of resources.