In that experiment subjects gave a response on a computer keyboard with the index fi nger of the right hand to words that named pleasant things and to names of fl owers. With the left hand they were to respond to another two categories – words that named unpleasant things and insect names. This was a very easy task. Then we made one minor change: We switched hands for the fl ower and insect names. Now subjects had to give the same response to pleasant words and insect names and a different response to unpleasant words and fl ower names. Immediately the task became hugely diffi cult. The slowing on a response-by-response basis was on the order of 300

milliseconds, which was a magnitude of impact nobody could have expected. We certainly did not expect it. I was the fi rst subject in the experiment. When I experienced the slowing I found to my surprise that I could not overcome it – repeating the task did not make me faster. If I tried to go faster, I just started making errors when I was trying to give the same response to fl ower names and unpleasant words. This was a mind-opener.