The Letter Memory Task(21) involved serial 2000-ms presentation of individual letters. The number of letters per trial varied randomly between 5, 7, 9 and 11 for a total of twelve trials and forty-eight letters. For each trial, at the termination of the presentation phase, participants were required to orally recall the final four letters from the presentation. The dependent variable was the total number of correct responses defined as recalling the correct sequence in its entirety. The Go-NoGo is a computerised task assessing inhibition and sustained attention.