To optimize survival, the nervous system has evolved to notice change and filter out the background. It happens in all of your five senses: eyes notice moving objects and not static ones; you stop noticing the refrigerator’s hum after a few days; you stop smelling something after five minutes. This is called habituation, and there are mechanisms operating at the cellular level to make this work. In other words, you’re better off understanding it and working with it rather than fighting it. And the proper way to circumvent habituation is to deliberately introduce salient, unpredictable stimulus, better known as change.

There are infinite ways of being unpredictable, but here I want to give you two techniques derived from behavioral psychology and animal training. The first is deliberate unpredictability, especially when it comes to doing nice things for your partner.

Behavioral psychologists and animal trainers call this implementing an irregular schedule of reinforcement. Let’s say you’ve been training a dolphin to jump, and you’ve been rewarding it with a single fish each time. The fish is the reinforcer