In memory research, participants may be given an unexpected task of recall or:

1. Recall and recognition make different demands on memory. 2. Recall means producing the information without cues. 3. After participants were presented with the words and questions, they were given an unexpected recall or recognition task. 4. Recognition instead asks whether an item presented now was seen before. 5. Making the task unexpected prevents deliberate rehearsal during the study phase. _Source: OpenStax Psychology 2e (CC BY 4.0), Ch 8 'Memory', sections 8.1-8.4_