A Model-Based Approach for Making Ecological Inference from Distance Sampling Data

We consider a fully model-based approach for the analysis of distance sampling data. Distance sampling has been widely used to estimate abundance (or density) of animals or plants in a spatially explicit study area. There is, however, no readily available method of making statistical inference on the relationships between abundance and environmental covariates. Spatial Poisson process likelihoods can be used to simultaneously estimate detection and intensity parameters by modeling distance sampling data as a thinned spatial point process. A model-based spatial approach to distance sampling data has three main benefits: it allows complex and opportunistic transect designs to be employed, it allows estimation of abundance in small subregions, and it provides a framework to assess the effects of habitat or experimental manipulation on density. We demonstrate the model-based methodology with a small simulation study and analysis of the Dubbo weed data set. In addition, a simple ad hoc method for handling overdispersion is also proposed. The simulation study showed that the model-based approach compared favorably to conventional distance sampling methods for abundance estimation. In addition, the overdispersion correction performed adequately when the number of transects was high. Analysis of the Dubbo data set indicated a transect effect on abundance via Akaike’s information criterion model selection. Further goodness-of-fit analysis, however, indicated some potential confounding of intensity with the detection function.

Exploring Online Sexually Explicit Material: What is the Relationship to Sexual Coercion?

With the popularity of the Internet, it is easy to access sexually explicit material. Past research has demonstrated that exposure to sexually explicit material in traditional formats (i.e. magazines and videos) may have an influence on male attitudes and behaviors towards females, but these effects appear to be minimal and dissipate over the long term. Though the body of literature examining Internet sexually explicit material is smaller, researchers have found little to no effects on attitudes or aggressive behaviors immediately after exposure. However, research regarding exposure to online sexually explicit material has not included forensically relevant variables. Previous research has suggested that undergraduate males who report engaging in sexually coercive or aggressive behaviors differ in terms of personality, attitudinal, and behavioral variables from individuals who do not report this type of behavior. Therefore, the purpose of this study was to examine the same personality and attitudinal variables that have been studied in previous research, but to extend this research by including behavioral variables related to the viewing of online sexually explicit material. Male undergraduate students were provided with a link to take an online survey examining personality (empathy, sensation-seeking, and psychopathy), attitudinal (rape myth belief, acceptance of interpersonal violence, and hostility towards women) and behavioral (online sexual compulsivity and online behaviors with regard to sexual material) variables. The relationship between these variables and sexually coercive behavior was examined. Results indicate there is a significant relationship between some scales related to empathy and viewing sexually explicit or degrading material. Further results indicated that individuals who identified as having engaged in sexually aggressive behavior endorsed more items related to online sexually compulsive behaviors. Exploratory analyses revealed that the amount, as opposed to the type, of sexually explicit material viewed appears to be more related to adverse outcomes.