Judgments of learning and the allocation of study time.

This is a commentary on the article by G. Mazzoni and C. Cornoldi (1993), in which they proposed an "item labor-in-vain effect" that they said is similar to the labor-in-vain effect reported by T. O. Nelson and R. J. Leonesio (1988). This commentary describes how the 2 effects differ in terms of the role of item selection and offers several comments about (and different interpretations of) Mazzoni and Cornoldi's findings. People's judgments of learning can serve as a useful basis to enhance overall learning by means of the allocation of extra study to the more difficult items. However, depending on the trade-off between the boost from extra study and the deficit from item selection, the effects of the extra study may or may not be evident in recall performance.