Habituation is defined as a decline in responding to a repeated stimulus. After more than eighty years of research, there is an enduring consensus among researchers on the existence of 9-10 behavioral regularities or parameters of habituation. There is no similar agreement, however, on the best approach to explain these facts. In this paper, we demonstrate that the Sometimes Opponent Processes (SOP) model of stimulus processing accurately describes all of these regularities. This model was proposed by Allan Wagner as a (...) quantitative elaboration of Priming Theory, which states that the processing of a stimulus, and therefore its capacity to provoke its response, depends inversely on the degree to which the stimulus is pre-represented in short-term memory. Using computer simulations, we show that all the facts involving within-session effects or short-term habituation might be the result of priming from recent presentations of the stimulus (self-generated priming). The characteristics involving between-sessions effects or long-term habituation would result from the retrieval of the representation of the stimulus from memory by the associated context (associatively-generated priming). (shrink)

The advances in treatment of HIV and the introduction of polymerase chain reaction assay for the virus now make it acceptable for HIV discordant couples where the male partner is seropositive to attempt to conceive through artificial insemination by husband (AIH) or via in vitro fertilisation. With undetectable viral load and washed sperm, there is minimal risk of transmission of HIV to the female partner, children, other patients, or staff. We describe the development of a programme of AIH for HIV (...) discordant couples and the reasoning behind offering such a programme. (shrink)

The success of assisted reproductive technologies (ARTs) worldwide has led to an accumulation of frozen embryos that are surplus to the reproductive needs of those for whom they were created. In these situations, couples must decide whether to discard them or donate them for scientific research or for use by other infertile couples. While legislation and regulation may limit the decisions that couples make, their decisions are often shaped by their religious beliefs. Unfortunately, health professionals, scientists and policy-makers are often (...) unaware of the way in which faith traditions view ART and decisions concerning the ‘fate’ of surplus embryos. In this paper scholars representing six major religious traditions provide a commentary on a hypothetical case concerning the donation or destruction of excess ART embryos. These commentaries provide a rich account of religious perspectives on the status of the human embryo and an insight into the relevance of faith to health and policy decisions, particularly in reproductive medicine, ART and embryo research. (shrink)