# Dating is an underactuated control system More fully, you can imagine dating as an underactuated control system with a plant, two control inputs, external inputs and measurement error.  Let’s break down each of these pieces. Each person in the relationship has some **intention** (either consciously or unconsciously) for where they would like the relationship to go. This is “what you’re looking for.” It could be anything from “sex” to “someone to talk to” to “a life partner.” In control system terms, this is each person’s controller’s set point. A person’s intention can vary based on the other person in the relationship, life situation etc. Intentions are contingent on so many things that it’s often hard to know what it is going in. How much conscious control someone has over their intention gets into a lot of out-of-scope shenanigans around preferences theory and the nature of consciousness. For example and perhaps controversially, I would argue that in the case of someone ‘sabotaging’ a relationship, their real intention is to end the relationship without taking direct action. Each person takes the difference between their intention and a **noisy measurement** of the relationship’s state. This delta could be roughly analogized to a completely *subjective* assessment of “How is it going?” If the state of the relationship is exactly what you want right now, the delta will be very small. If you want the state of the relationship to be different (even if you are happy with the trajectory it’s on) the delta will be non-zero. Each person then acts on that noisy measurement. Notably, this **control input** has both a ‘thinking’ and ‘acting’ component. Most people realize that for most relationships you can’t just drive directly for your intention. This is where the ‘underactuated’ property of the system comes in. [[An underactuated system cannot drive directly towards its target]] because it doesn’t have enough ‘control authority.’ Think of a swimmer sucked into a riptide: they aren’t powerful enough to swim back to the shore so they must first swim perpendicular to the shore (changing the state of the system) and *then* swimming back to the shore. The inverted pendulum is the classic under actuated system — it has two degrees of freedom but is only able to move its base. In order to keep the pendulum vertical it needs a clever control input. Inverted pendulums are a classic underactuated system. The underactuated nature of people’s control inputs means that they *must* have a ‘sophisticated control policy’, despite the fact that more complex control policies are more prone to failure. This is a fancy way of saying that many people’s desire for relationships to be ‘straightforward’ is misguided. People want to be romanced and feel a certain way. [[Human interactions are path dependent]] — the same conversation that is totally chill later in a relationship might stress it to the breaking point early on. Both people’s control inputs feed into the natural **relationship dynamics**. Anybody who has been in a relationship knows that a given input doesn’t always have the expected output. Maybe it pokes an old trauma or they respond in a way that annoys you. Maybe someone isn’t emotionally receptive. These dynamics are a ill-defined muddled bundle that can’t be directly controlled and can respond in nonlinear ways. To compound the control problem challenge **External Inputs** also feed into the relationship dynamics. These are just, y’know, *everything else in life*. Job, family, bad sleep, global pandemics. One way this model might be inaccurate is that people’s intentions for a relationship are not fixed by some unmoved mover. Over time someone’s intention could shift from wanting a casual relationship to a serious one. *However* from my personal experience and talking to/observing other people this is less common than fictional narratives might suggest. Is it kinematically constrained? Kinematics are one way to capture the fact that [[Human interactions are path dependent]], but it would also mean that certain configurations are impossible (and you could get singularities and such). I suspect this isn’t actually the case. Instead, the constraints are continuous functions that could be very hard to reach but there’s no hard rule making them impossible the way that kinematics would. It’s fun to think about how this model ties to other big relationship topics. Take [[Trust]] for example. I would argue that trust ‘buffers’ the relationship dynamics — it makes them less responsive to inputs that could send the relationship into a bad place and gives you time to see potential problems and apply the inputs to correct them. ### Related * [[Trust takes time]] * [[Loyalty thresholds depend on your trust in a person and the size of the breach]] * <!-- #evergreen --> [Web URL for this note](http://notes.benjaminreinhardt.com/Dating+is+an+underactuated+control+system) [Comment on this note](http://via.hypothes.is/http://notes.benjaminreinhardt.com/Dating+is+an+underactuated+control+system) <!-- {BearID:395776BD-443B-44B5-8839-42848700090E-461-00020EA0B42AF0A2} -->