… pigeons pecking at a disk to get food. Instead of getting food at every single peck (predictable), Skinner found something else: the rate of response — the number of times pigeons pecked at the disk — increased when the reward happened at a variable schedule of reinforcement. That is, almost randomly.
This leads to an interesting ethical dilemma: To make a truly effective hook, we have to capitalize on users’ negative emotions. To keep them using the product, their negative emotions (and thus the need relief) need to stick around.