A biologist wants to know if a particular drug affects the developing brains of rat pups. She has one condition in which the rat pups receive a placebo and one condition in which the rat pups receive the drug. If she decides to use a within-subjects design, will counterbalancing help reduce order effects?

• Counterbalancing will help, because order effects will be minimized or eliminated by varying the order in which the conditions are experienced.
• Counterbalancing will help, because each rat pup will act as its own control in the study.
• Counterbalancing will not help, because those rat pups that receive the drug first might have brain changes that will not go away when the placebo is administered.
• Counterbalancing will not help, because there are only two conditions. A third condition would be needed to make counterbalancing useful.