Visual recognition involves storing and retrieving memories. Neural activity, triggered by the eye, forms an image in the brain’s memory system that constitutes an internal representation of the viewed object. When an object is encountered again, it is matched with its internal representation and thereby recognized. Controversy surrounds the question of whether recognition is a parallel, one-step process or a serial, step-by-step one. Psychologists of the Gestalt school maintain that objects are recognized as wholes in a parallel procedure: the internal representation is matched with the retinal image (retinal image: 眼膜图象) in a single operation. Other psychologists have proposed that internal representation features are matched serially with an object’s features. Although some experiments show that, as an object becomes familiar, its internal representation becomes more holistic and the recognition process correspondingly more parallel, the weight of evidence seems to support the serial hypothesis, at least for objects that are not notably simple and familiar.
17. The author is primarily concerned with
(A) explaining how the brain receives images
(B) synthesizing hypotheses of visual recognition
(C) examining the evidence supporting the serial recognition hypothesis
(D) discussing visual recognition and some hypotheses proposed to explain it（D）
(E) reporting on recent experiments dealing with memory systems and their relationship to neural activity
18. According to the passage, Gestalt psychologists make which of the following suppositions about visual recognition?
I. A retinal image is in exactly the same forms as its internal representation.
II. An object is recognized as a whole without any need for analysis into component parts.
III. The matching of an object with its internal representation occurs in only one step.
(A) II only
(B) III only
(C) I and III only
(D) II and III only（D）
(E) I, II, and III
19. It can be inferred from the passage that the matching process in visual recognition is
(A) not a neural activity
(B) not possible when an object is viewed for the very first time
(C) not possible if a feature of a familiar object is changed in some way
(D) only possible when a retinal image is received in the brain as a unitary whole（B）
(E) now fully understood as a combination of the serial and parallel processes
20. In terms of its tone and form, the passage can best be characterized as
(A) a biased exposition
(B) a speculative study
(C) a dispassionate presentation
(D) an indignant denial（C）
(E) a dogmatic explanation