How many points should be awarded for interactive textbook reading assignments?

New college engineering textbooks and other online learning materials use activities like interactive questions to engage students and improve learning. Some such materials use a "safe" learning approach where activity solutions are readily available to students, as opposed to being graded like a homework assignment. Instructors have inquired how few course points are sufficient to ensure students complete such assigned activities. Furthermore, some wonder if assigning course points might lead students to "cheat the system" by revealing solutions to quickly earn points, rather than earnestly attempting to answer the questions. We analyzed behavior data of 1,394 students in 8 engineering classes at different colleges. We found that surprisingly few course points - just 5 or 10 points, and as few as 2 points - were sufficient to achieve over 90% average completion of activities by students. For comparison, assigning no points yielded only about 50% completion. Furthermore, we found that assigning points had only a minor impact on students earnestly attempting to answer questions, versus showing themselves the answer first, with earnestness changing only modestly from 92% to 86% when points were assigned.