i think people are talking about 2 different tricks here
the first one (the one i was talking about) was where there were 4 ciggy boxes next to each other on the table, and spencer would look away while a housemate touched one of the boxes for 3 seconds. Spencer then put his hand over each box and was able to tell which box the housemate touched.
the second was where they had 9 ciggy boxes laid out on the table in a 3x3 formation, and someone would choose a box while spencer was not looking. Spencer would then come back and someone would say "is this it", "is this it" etc pointing to different boxes. i think i know how this trick is done.
anyway if anyone knows the first trick i would be very happy