A continuation of work reported in this journal, 1925, 8, 363-380, to determine "the effects of fatigue induced through loss of sleep on the learning process." 5 subjects worked, 3 as an experimental and 2 as a control group, tossing balls into a basket 12 feet distant, transcription on paper of a text into the Morse code, and mental multiplication of two two-place numbers. There was an 18-day pre-insomnia series, followed by 3 days of reduced sleep, and then 6 days post-insomnia. No sleep was taken on the 3 days by the experimental group (66 hours). The main differences noted were: inability to maintain attention for a period; decreased speed with little or no effect on accuracy; effect of sleep loss is immediate; time needed for recovery varies with individual--generally a single night; "fatigue does not lessen ability, but affects . . . motivation, interests, initiative, attention and concentration, which are necessary to the learning process." No mention is made of Laslett's more extensive investigation reported previously in this journal. (PsycINFO Database Record (c) 2006 APA, all rights reserved)