Metacognitive experiences (ME) comprise feelings and judgments / estimates which monitor cognitive processing. They form online metacognition and differfrom metacognitive knowledge, i.e., ideas regarding persons, tasks, strategies, which may also be active during problem solving. Feelings have the distinctive feature of pleasantness / unpleasantness and monitor good functioning, i.e., fluency of processing, obstacles or interruptions, and match / mismatch between one’s goals or concerns and actual conditions. Metacognitive experiences can be measured with rating scales before or after problem solving (that is, prospectively or retrospectively).