Definition
Unpredictability is the general quality of being hard to forecast. Where surprise is a single calculated jolt and mixed signals a specific oscillation, unpredictability is the steady-state condition those tactics aim to produce: a person whose next move the target can never quite anticipate.
Greene treats it as a guard against the seducer's true enemy — familiarity. A fully forecastable person is, in attentional terms, already absent. Unpredictability keeps the target's mind perpetually working to model someone it cannot finish modeling.
Why it matters
How it works
The unpredictable seducer keeps a margin of the unknown — withholding parts of themselves, varying their behavior, never resolving into a complete and stable picture. The target's mind, which automatically builds models of the people around it, can never complete this one, and so it keeps returning to the work.
That unfinished modeling is experienced as intrigue. The target reads their own inability to predict the seducer as evidence that the seducer is deep, complex, endlessly interesting.