Section 1: Sensing the World Around Us

2. Sensory adaptation, an adjustment in sensory capacity following prolonged exposure to stimuli. Decline in sensitivity is due to the inability of nerve receptors to constantly fire messages to the brain. Receptor cells are most responsive to changes in stimulation and constant stimulation is not effective in producing a reaction. Adaptation to the context of one stimulus alters responses to another. If our senses were constantly bombarded by stimuli that was intense, we would have a constant high rate of stimulation.

Section 3: Hearing and the Other Senses

5. Benefits of increased sensory capacity might allow us to see great distance. We may also be able to hear sounds from far away. Our sense of touch could cause us to have increased pain from cuts and burns. Science already has invented equipment that allows these things: "Sonic Ear" advertised to hear long distances, new surgery that improves eyesight, etc. These could be great scientific achievements but, to have our senses bombarded by increased stimuli doesn't seem to have overall advantages-how would we distinguish necessary/ unnecessary stimuli?

6. Sensitivity to pheromones may have developed differently for humans because as the culture has evolved, sending out messages that you were available for sexual activity could have been dangerous (sent to others who were not potential partners). Also, societies now set up rules for sexual activity and partnerships (different from that in the animal world).