nBack train & fruit version

The nBack is a cognitive task that is geared to measure the executive functions of our cognitive system. In a sketch, executive functions allocate high order cognitive functions (e.g. working memory, attention, long term memory etc.) in order to solve complex tasks in every day life. Two executive functions that are involved in this task are: MEMORIZATION: keep track of the fruit you've just seen to check whether it matches with the fruit you will see. VERIFICATION and ACCESS TO MEMORY: check whether the fruit you see matches the one you saw in 2 positions backwards. INHIBITION: if the fruit you see doesn't match it, do not press the SPACE BAR... but memorize if for the next trials. The 2nBack version is very easy for adults, but it's challenging for young children (4-8 year old). This version will be tested with infants of this range of age. bugs: it seems that sometimes it does not readily get the KEYDOWN SPACE BAR event... I'm not sure if it's because I run in on my mac (I'll check it with a win XP 32 PC)