Figure 5

Experimental results. A Recognition performance for all participants who passed the qualification task (see Methods). B Recognition performance for participants that were perfect in the 2-back task. The experimental retention curve (recognition performance vs the lag between word presentation and delayed recognition task positions, solid green curve) declines for both groups. We can observe that performance in the 2-back task (solid blue curves, time here indicates the position of the recognition task) is declining with time, It is generally assumed that working memory capacity is 3–5 items, and therefore the drop of performance in the 2-back task indicates that a progressively smaller fraction of words was acquired toward the end of the trial due to fatigue, loss of attention, or other reasons. Selecting the group of participants (in panel B) that are perfect in the 2-back task, we ensured that all the words were acquired during presentation. For this group of participants, the performance in the 10-back task (orange solid curves, time indicates query position) remains constant throughout the experiment (compare with faint orange line representing mean performance in the 10-back task). The dashed lines represent theoretical retention curves computed with equation (10) corrected for guessing (see Methods), for different number of dimensions n