Successive Approximations
The intermediate steps toward a target behaviour that are reinforced during shaping.
Successive approximations are the stepping stones of shaping. Each one is a version of the target behaviour - closer than the last, not quite the final form yet - that gets reinforced until the next step up becomes reliable.
The concept is simple but the application requires judgment. What counts as a meaningful step forward? How different does the approximation need to be from the previous one before you raise the criterion? There's no formula. You're reading the learner's performance and making a clinical decision about when they're ready for the bar to move.
The reason the term matters beyond just 'steps in shaping' is that it reframes how you look at incomplete or imperfect behaviour. A learner who is approximating a target isn't failing - they're at a specific point in a trajectory. That reframe changes how you respond. You're not correcting an error; you're reinforcing progress and preparing to raise the criterion when the data support it.