We think we see things as they are but we put our own perception on it. An internal model of the world. Our environment shapes the way we view the world. Prior knowledge tries to infer what is happening in the present. Perceive it immediately and the brain processing information. However, some people suffer from syndromes such as apperceptive agnosia where people are able to effectively allocate attention to locate the object and perceive the parts, they are unable to group together the parts they see and name the object accurately.
In the research study by Vecera, Shaun P.; Gilds, Kendra S (1997) “What Is It Like to Be a Patient with Apperceptive Agnosia?” they wanted to understand the visual processes damaged in apperceptive agnosia, they first review this syndrome and present a case study of one such patient, patient J.W., then they review several theoretical accounts of apperceptive agnosia, and they concluded that studies of the patients themselves may not allow us to discriminate between the various explanations of the syndrome.
As they demonstrated, one can potentially distinguish between these rival hypotheses by attempting to simulate apperceptive agnosia in normal subjects; data from the patients themselves seem to be unable to resolve the various accounts. The results from normal subjects suggested that by eliminating non accidental grouping cues we could replicate a series of results exhibited by one apperceptive agnostic patient whom they have tested, patient J.W.
While we may be forever unable to understand the visual experiences of an apperceptive agnosic patient, the study of such patients can provide an understanding of this neuropsychological syndrome, as well as an understanding of normal visual processing mechanisms.