Why does a distraction cause a longer reaction time? Does it have something to do do with the fact that the individual isn't concentrating on reacting to the stimulus, so it takes longer for it to be processed? How can this be out in terms of neurones and neurological pathways? what is happening for there to be a delayed reaction time?

When one processor is running two processes, A and B, it is not running them simultaneously: it is switching between them. **The switching** between A and B **takes time** \---hence the delay.