Letter cancellation test

Cancellation tests picking out and marking numbers, letters and geometric shapes according to a given criterion... 

Another test requiring focused attention is digit or letter cancellation, in which subjects mark through a certain numeral in a page of random numbers or a certain letter in a page of text or random letters. The typical duration of cancellation tests is 1 to 2 min. Two studies reported that diazepam (10 or 15 mg)157 and lorazepam (1 and 2 mg)124 impaired digit cancellation performance. Interestingly, Brown et al.157 found that impaired focused attention was not correlated with the ability to encode associative information. These studies confirm numerous previous studies that reported benzodiazepine-induced decrements in cancellation tests.7... 

Indometacin. Diazepam 10 to 15 mg impaired the performance of a number of psychomotor tests (digit symbol substitution, letter cancellation, tracking and flicker fusion) in 119 healthy medical students. It also caused subjective drowsiness, mental slowness and clumsiness. When indometacin 50 or 100 mg was given the effects were little different from diazepam alone, except that the feeling of dizziness (common to both drugs) was increased and caused subjective clumsiness. ... 

Eye-hand choice reaction time is tested as the speed to cancel by tapping a keypad, a 4 inch letter that appears on the screen of a laptop computer. Twenty trials repeated twice and the median time of last 7 trials in each run is recorded. Simple, same letter, reaction time takes 1/4 of a second, 250 ms while choice between 2 letters takes twice as long, 500 ms. Many tests are faster in women, most deteriorate with aging after 25 years and for people with more years of educational attainment scores are higher. ... 

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