Abed's notebook is a special journal he kept in his sophomore year at Greendale. He used it to chart the fluctuating behavior of his female study group members towards him. He continued this practice even after realizing the inappropriate nature of his research. "Abed's notebook" first appearance was in the Season Two episode "Cooperative Calligraphy".
In the study group's second year at Greendale, Annie's pen went missing one day after they completed another Anthropology diorama project. At Annie's insistence, an intensive search began of Group Study Room F. This escalated into a search of the study group member's personal belongings as Abed had his backpack inspected. Britta noticed Abed's notebook had her name along with Shirley and Annie's inside of it. Included were charts, diagrams and daily logs which Britta realized were monitoring the women's menstrual cycles. An explanation was demanded from Abed who was forced to admit he kept the notebook to improve relations with them. His difficulty with relating to people and accidentally saying inappropriate things happened more frequently with the women in the study group.
The women find out about Abed's notebook.
Abed started studying this phenomenon and eventually he understood exactly what the data represented. By then his research yielded positive results so he kept doing it. The women were upset by his actions particularly Annie whom Abed offered a hanky and some chocolate. Annie caught on to what he was doing and angrily rejected his offerings which led Pierce to express his admiration of Abed's research. Pierce then asked to look at the notebook and the women in unison vehemently refused. Pierce was taken aback by their response and commented that the "synch up" theory was true. When it was Shirley's turn to have her bag searched a pregnancy test was found. Shirley admitted she might be expecting since she and her ex-husband hooked up over Labor Day. However, Abed disagreed and consulted his notebook. According to his records, the notebook data showed that she was ovulating around Halloween the month before so she couldn't be pregnant by Andre ("Cooperative Calligraphy").