Two major functions of the visual system are discussed and contrasted. One function of vision is the creation of an internal model or percept of the external world. Most research in object perception has concentrated on this aspect of vision. Vision also guides the control of object-directed action. In the latter case, vision directs our actions with respect to the world by transforming visual inputs into appropriate motor outputs. We argue that separate, but interactive, visual systems have evolved for the (...) perception of objects on the one hand and the control of actions directed at those objects on the other. This 'duplex' approach to high-level vision suggests that Marrian or 'reconstructive' approaches and Gibsonian or 'purposive-animate-behaviorist' approaches need not be seen as mutually exclusive, but rather as complementary in their emphases on different aspects of visual function. (shrink)

The McCollough effect, an orientation-contingent color aftereffect, has been known for over 30 years and, like other aftereffects, has been taken as a means of probing the brain's operations psychophysically. In this paper, we review psychophysical, neuropsychological, and neuroimaging studies of the McCollough effect. Much of the evidence suggests that the McCollough effect depends on neural mechanisms that are located early in the cortical visual pathways, probably in V1. We also review evidence showing that the aftereffect can be induced without (...) conscious perception of the induction patterns. Based on these two lines of evidence, it is argued that our conscious visual experience of the world arises in the cortical visual system beyond V1. (shrink)

First Published in 1999. Routledge is an imprint of Taylor & Francis, an informa company.

In lieu of an abstract, here is a brief excerpt of the content:The Power of PersuasionG. Bennett HumphreyA long white coat, the title of doctor, a practiced professional persona and an appointment to the staff of a prestigious university medical center allows the physician to be a persuader of clinical decisions affecting patient management. When this power of persuasion is used to encourage patient compliance with a therapeutic regimen that might be curative for a fatal disease, there is justification for (...) trying to influence the patient to make choices resulting in a positive outcome. But when a physician is asking permission to enter the patient into a research protocol where the primary goal of the study is the hope of advancing knowledge, then much thought needs to be given to the potential abuse of this power of persuasion.In the 1960s, I found myself having to think about recruiting children into research protocols. I had just finished two years of residency in internal medicine and wanted to pursue a career in academic medicine. My primary interest was in laboratory research. To strengthen my training in research, I had competed for a position as clinical fellow in a western university. The fellowship program was designed to expose young physicians to both clinical and laboratory research. The first year was spent on one of the clinical research wards and the second year in a research laboratory. The program was open to residents from surgery, medicine and pediatrics but because there was a shortage of pediatricians in the program, I was required to work on the children’s leukemia ward for one year.The learning curve was steep during the first few months. Naturally, the faculty in pediatrics and the medical literature gave me a technical education in the use of protocols for therapeutic treatment of leukemia. For example, the first protocol used was designated as Phase III, and the goal was to try to cure the patient. A remission could be achieved in over 90 percent of children but the disease recurred. The median duration of these remissions in the mid–1960s was one year. A relapse was followed by progressive disease and death in a matter of weeks, but a new drug of unknown efficacy could be administered. This was a Phase II protocol, and while there was a chance of prolonging life for a month or so, the primary goal was the identification of drugs anti–leukemic activity.The pediatric leukemia ward experience for me as a fellow was unusual. There was more to learn than the treatment of leukemia. To my surprise, the children and their mothers gave me insight into the care of pediatric patients. Each month, the patients were admitted for five days of intravenous chemotherapy. The first day was traumatic with venipunctures, bone marrow aspirations and the establishment of an IV for the daily infusion of drugs. The remaining four days were for social rounds: listening to the children who liked to talk; talking with the ones who liked to listen; putting puzzles together with some toddlers; responding to a request to listen to the heart of a much loved teddy bear; exchanging jokes and riddles; stories about school, the family dog, or a favorite friend; enjoying the banter of the adolescents; and not invading the privacy of a few who didn’t like me, the ward or the therapy. These children were sharing their childhood with me and it took couple of months for me to recognize I was bonding with these little patients. I observed and listened to the mothers caring for their children and stood in awe of the resources that they brought to bear on having children with a fatal disease. A feeling of mutual respect and trust developed between these mothers and me. For an internist, these experiences were profound and very different from my experience treating adults.A professor, an internationally known researcher in the field of leukemia, was in charge of the ward. Formal rounds were conducted on Tuesday mornings when the result of the bone marrow aspirates and the toxicity of the chemotherapy were reviewed. The day–to–day responsibility for [End Page 101] treatment and informing the mothers on the remission status on Mondays was my responsibility... (shrink)