What is the "performance versus learning" distinction, and why does it matter?

Performance = how well you do right now; learning = durable change you can still show later — and they can move in opposite directions.

Educational scientists (notably Nicholas Soderstrom and Robert Bjork) stress that what you observe during study — smooth, error-free performance — is a poor and sometimes misleading index of learning. Conditions that boost immediate performance (cramming, re-reading, having the answer in view) often produce little lasting memory, while conditions that depress immediate performance (spacing, self-testing, making errors) tend to produce more. The tip: distrust fluency as a gauge of learning; ask instead "could I still do this cold in a week?"