閱讀理解-1

Whatdoes a scientist do when he or she "explains something? Scientificexplanation comes in two forms: generalization and reduction. Mostpsychologists deal with generalization. They explain parlicular instances ofbehavior as example of general laws. For instance, most psychologists wouldexplain a pathologically (病態)strong fear of dogs as example of classical conditioning. Presumably, theperson was frightened earlier in life by a dog. An unpleasant stimulus waspaired with the sight of the animal (perhaps the person was knocked down by avigorous dog and the subsequent sight of dogs evokes the earlier response offear.
Most physiologists deal with reduction. Phenomena are explained in terms ofsimpler phenomena. For examjle, the movement of a muscle is explained in termsof changes in the membrane (生物膜)ofmuscle cells, entry of particular chemicals and interactions between proteinmolecules within these cells. A molecular biologist would "explain"these events in terms of forces that bind various molecules together and causevarious parts of these molecules to be attracted to one another.