So, we have to choose the important stuff to attend to, and ignore the rest. Cherry study - read in class. All information is processed, but only one item enters awareness and is later recalled.
Habituation reduces response of neurons responding to specific repeating stimuli.
Sensitization increases responses generally as a stimulus continues or multiple stimuli occur - overall heightening of awareness. In scanning, we are immediately aware of things that differ by a single physical property. Number of distractors is irrelevant, suggesting scanning is taking place in parallel. We are not immediately aware of conjunctions of features. Instead, need to scan serially for these.