To Tell the Truth
Allison's cousin arrives at the school and says she needs to do a psychology experiment in order to help her do her paper for her psychology class at college. Anyone who agrees promises to tell only the truth for 48 hours. After that she will interview them and find out how things went.
Only Pamela refuses to help out, which is totally expected of her.
Psychology experiments can backfire as does this one. I was taking a class in college in psychology and the teacher was doing a psych experiment. The problem is that he didn't tell any of the students he was doing that and never asked anyone's permission. We were given frequent quizzes which he would (again unknown to us) separate into groups which include giving the student a high grade and a positive comment, a high grade and a negative comment, a low grade and a positive comment, and a low grade and a negative comment (I'm assuming he also had a fifth group, an accurate grade and some type of comment.)
This went on for quite a while and the students got very, very angry because the grades and comments made no sense to the students. For example, someone could be absolutely positive that they nailed the quiz yet get a very low grade and a negative comment. It's natural to see how that person would be very upset. Or a person who got a high grade and a negative comment which, naturally, would seem totally incomprehensible.
Anyhow, the situation got so bad the students were so angry that the teacher finally realized his little experiment was not working and he explained things and stopped doing the experiment.
In the Canby Hall experiment the girls and the three boys find out that telling absolutely nothing but the truth for 48 hours can cause severe problems. Shelly gets the worst situation, having to take Patrica to the hospital then not let anyone know that the head of the school had a health problem. She was seen driving the headmistress's car back to the school and from then on a tremendous amount of pressure was put on her.
The girls had problems with each other, with their boyfriends, with their crushes and even with the other students and the groundskeeper. Pamela has been going around and fueling the fire whenever she can just to make matters worse.
In the end things work out all right, of course, but the book shows how being nothing but totally truthful can cause people problems.