Exposure is all about reinforcement in the brain. Whenever we engage in a habitual behavior in response to something we fear, we reinforce that fear. If we are afraid of spiders and back away from them, we reinforce that fear. Imagine a great fear of spiders. You see one in the bedroom. You run out of the bedroom and get someone else to kill it. Or you spray half a can of pesticide in your room. Or you call a pest control company. I’ve known one person who refused to sleep in her bedroom for three months after seeing a spider there!
The way it works is that they become more and more anxious as they approach the feared object or situation. In the case of spiders, if I’m afraid of them and I have to kill one, I become more and more afraid as I approach it. Maybe I have a shoe in my hand, poised to smash the creature. My heart is pounding, my pulse is racing, I’m almost hyperventilating. I’m terrified! I get closer and closer, sweating bullets. I suddenly decide that I can’t handle it! I turn heel and flee from the room, calling my neighbor and asking her to come over and kill the thing. The moment I run away, how am I feeling? Relieved! My pulse slows and my breathing returns to normal. I wipe my brow with a shaking hand. Whew! That was close!
Look at what I did to my brain. I had increasing anxiety as I drew closer and closer to the spider. Then I decided I couldn’t do it. I fled the scene and I had an enormous sense of relief. That relief – that feeling – was a reward. I rewarded myself for fleeing from the spider. I’ve taught myself, quite literally my brain, that spiders are indeed very dangerous creatures. I know this because of the feeling of relief I had when I left. The result is that I actually increase my fear. I have made myself a little bit more afraid of spiders every time I exit.

... I think her behaviour towards strange dogs in the last week is worse than before going to class last Sunday