Helwig NCE & CPCE Human Growth and Development Practice Test 2026 – All-in-One Guide to Mastering HGrD!

Fixed interval schedules deliver reinforcement after a constant amount of time has passed since the last reinforcement, provided a response occurs. This means the timing is the key factor—not how many responses are made. Behavior tends to rise as the end of the fixed interval approaches, producing a scalloped pattern of responses. That’s why “reinforcement after a fixed period of time” is the correct description. The other options point to different schedules: reinforcement after every response is continuous reinforcement; reinforcement after a variable period is a variable interval schedule; reinforcement after a fixed number of responses is a fixed ratio schedule.