This is a test of simple arithmetic. You start with a number , say 833, and have to subtract seven from it repeatedly, so:  
834  827  820  813  806  799      

There are several automated version of this test. We use one with a YesNo choice. 

First you see a number, and memorise it 
834 
Then the next number appears. 827 is 7 less than 834, so you tap YES 
827 
Then the next number. 818 is not 7 less than 827, so you tap NO 
818 
Then the next number. 811 is 7 less than 818, so you tap YES 
811 
We record the reaction times averaged over the test, and the total number of errors. This test can be run on a tablet computer or a Javaenabled mobile phone. 

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