The "d2 test of attention" has been used in studies regarding sleep deprivation due to night shifts in hospital staff, in order to determine whether sleep deprivation has an impact on performance. However, by repeating the test there appears to be a test-retest effect, as the participants improve when performing the test more than once. The aim of this study is to determine, whether the "d2 test of attention" has a test-retest effect.

20 surgeons and 20 surgical nurses will be included in this study. They will be asked, after thorough instruction, to perform the d2 test of attention after a designed schedule. The participants will on day 1 and 2 perform the test 3 times consecutively at intervals of 5 minutes. On day 3, 4 and 5 the test will be repeated only once. After the 5th day follows a 7-day-break. On day 13 the test will again be performed once.

Inclusion Criteria:

- Nurses and surgeons at the department of Surgery, Herlev hospital. Age 22-55 years.

Exclusion Criteria:

• Known sleep disturbances and attentional deficits, previous use of the d2 test of attention, use of central stimulating drugs