When mechanistic models explain

Not all models are explanatory. Some models are data summaries. Some models sketch explanations but leave crucial details unspecified or hidden behind filler terms. Some models are used to conjecture a how-possibly explanation without regard to whether it is a how-actually explanation. I use the Hodgkin and Huxley model of the action potential to illustrate these ways that models can be useful without explaining. I then use the subsequent development of the explanation of the action potential to show what is required of an adequate mechanistic model. Mechanistic models are explanatory.     

My place,your place,and no place: Behavior settings as a risk factor for HIV-related injection practices of drug users in Baltimore,Maryland

Information is sparse on the social context of illicit drug injection behaviors and their relationship to HIV infection. This study examined relationships between injection settings, injecting with others, and HIV risk behaviors of sharing needles and not cleaning contaminated needles in a sample of 630 inner-city injecting drug users in Baltimore, MD. Through open-ended interviews, five primary settings of injection behavior were identified. These settings included one's own, friends' and mother's residence, shooting galleries, and semipublic areas. Most participants reported injecting in their own residence (92%) and friends' residence (86%) in the prior 6 months. In a multiple regression analysis, injecting at friends' residence, in shooting galleries, and in semipublic areas and frequency of injecting with others were significantly associated with frequency of sharing uncleaned needles, “slipping” (i.e., failure to disinfect shared needles), and not always cleaning used needles before injecting. Results suggest that interventions may benefit from targeting settings as well as behaviors to reduce the spread of HIV. This research was supported by grants DA04334, DA05911, DA06313, and DA08985 from the National Institute on Drug Abuse.     

Gender, Somatization, and Psychopathic Traits in a College Sample

The structure of psychopathic traits and their association with somatization symptoms were investigated in a sample of 199 undergraduate college students enrolled in introductory psychology classes. Using multiple measures of psychopathic traits, an iterated principal axis (IPA) analysis revealed two dimensions of psychopathy that were similar to ones typically found in forensic samples. One dimension focused on a cold, callous, and unemotional interpersonal style and the second dimension focused on an impulsive and antisocial lifestyle. These two dimensions emerged for both men and women, although the correlation between the two was somewhat higher for men than women. Also, the callous and unemotional dimension was negatively correlated with somatization symptoms, and the impulsive and antisocial dimension was positively associated with somatization symptoms. This pattern of associations was similar for both men and women and it suggests that somatization symptoms may be one aspect of the high rate of negative affectivity experienced by antisocial individuals.     

Extrasensory perception,near-death experiences,and the limits of scientific knowledge

If mental state can influence the external world, or if alternate dimensions of reality are accessible only in certain mental states, then important aspects of the universe are unknowable with current scientific tools. Near-death studies suggest that both those conditions may occur. Thus the exploration of NDE-like phenomena requires a radically new scientific paradigm.