Dating as a way to prove that he is normal
During his lifetime, Colin dated a number of girls but each time his relationships ended up badly. Despite this, Colin continued to want to date other girls because of the way they made him feel. Colin mentions that all his life, he was judged because of his capabilities and that he never felt like he fit in anywhere. The only time when he felt normal was when he was dating. This idea is a recurrent motif in the novel and it is mentioned almost every time when Colin thinks about his past relationships.
Being a prodigy
All his life, Colin was told that he is special because of his capability of learning almost everything in a short period of time. Being a prodigy meant that people expected him to do great things from an early age and when he failed to do that, they looked down on him and regarded him with superiority. In high school, Colin felt special because it was clear that he was the most intelligent one in his class. When he finished high school however, this changed and Colin became afraid of becoming normal. This fear is a common motif in the novel and Colin mentions it frequently.
Biting my thumb
Another common motif in the novel is the fact that Lindsey has a nervous tick, biting her thumb whenever she gets nervous or the situation is uncomfortable for her. Her action is mentioned numerous times in the novel so it becomes a common motif and one of the things that characterize her.
Calling her
Another common motif in the novel is the idea that Colin wants to call Katherine and talk with her one more time. Colin tells Hassan about his desire to call Katherine and he manages to convince Colin not to do it on certain occasions. In chapter 10 however, Colin calls Katherine and the talk he had with her made him realize that he was over the relationship and over Katherine.
Relationships do not last
Another common idea in the novel is that relationships do not last. Colin, from his own experience, can tell from certain that every relationship will eventually fail and we see this also in Hassan’s case and in Lindsey’s case who are cheated on by their significant others. The practice is so common that Colin even developed a formula to calculate the possibility of one couple remaining together for an extended period of time and the most probable time when their relationship will end.