Structural equation model testing and the quality of natural killer cell activity measurements

BACKGROUND: Browne et al. [Browne, MacCallum, Kim, Andersen, Glaser: When fit indices and residuals are incompatible. Psychol Methods 2002] employed a structural equation model of measurements of target cell lysing by natural killer cells as an example purportedly demonstrating that small but statistically significant ill model fit can be dismissed as "negligible from a practical point of view". METHODS: Reanalysis of the natural killer cell data reveals that the supposedly negligible ill fit obscured important, systematic, and substantial causal misspecifications. RESULTS: A clean-fitting structural equation model indicates that measurements employing higher natural-killer-cell to target-cell ratios are more strongly influenced by a progressively intrusive factor, whether or not the natural killer cell activity is activated by recombinant interferon γ (rIFN γ). The progressive influence may reflect independent rate limiting steps in cell recognition and attachment, spatial competition for cell attachment points, or the simultaneous lysings of single target cells by multiple natural killer cells. CONCLUSIONS: If the progressively influential factor is ultimately identified as a mere procedural impediment, the substantive conclusion will be that measurements of natural killer cell activity made at lower effector to target ratios are more valid. Alternatively, if the individual variations in the progressively influential factor are modifiable, this may presage a new therapeutic route to enhancing natural killer cell activity. The methodological conclusion is that, when using structural equation models, researchers should attend to significant model ill fit even if the degree of covariance ill fit is small, because small covariance residuals do not imply that the underlying model misspecifications are correspondingly small or inconsequential

Navigating ambivalence: How heterosexual young adults make sense of desire differences

The miscommunication hypothesis is the assumption that many incidents of acquaintance rape and coercive sex follow from miscommunication between men and women. This hypothesis is entrenched in popular, academic, and judicial understandings of sexual relationships. Recently some evidence has suggested that there is little miscommunication between sexual partners and that the hypothesis does not explain acquaintance rape or other forms of sexual violence. The present study used qualitative methodology in which men and women were asked to imagine themselves in a particular heterosexual dating situation and write what they think happened between the beginning (when sex was refused by one partner) and the end (when sex happened). Thematic analysis of the data found no evidence for miscommunication between partners under conditions of differences in desire. Instead, ambivalence about sexual activity was commonly described by women and men and was most often resolved to both parties satisfaction. Coercion by men was present in a minority of narratives under conditions of clear understanding of women\u27s refusals. The study thus provides a rich, experience-based representation of heterosexual sexual activity, with considerable potential for the development of effective education campaigns. © 2014 The Society for the Scientific Study of Sexuality