It is widely believed that semantic activation from print is not capacity limited (i.e., that it does not need attentional resources). Prior research has tested this assumption by examining the Stroop effect in the context of the psychological refractory period (PRP) paradigm. These studies yielded additivity of the Stroop effect and SOA on RT, consistent with the hypothesis that semantic activation is itself capacity limited (given demonstrations that prior processes are not capacity limited). There is, however, an alternative explanation for such additivity: performance optimization (Miller and colleagues, 2009). Given that participants in PRP experiments are told to respond as quickly as possible, they may opt to process serially to improve performance. We investigated whether additivity of the Stroop effect (standard and semantic) and SOA in the context of PRP is best explained in terms of a structural bottleneck or performance optimization.

The standard Stroop effect (which typically uses color words that form part of the response set) is robust and welldocumented in mean RT. Ex-Gaussian analyses reveal that this effect is seen in the mean of the normal distribution (mu),in the standard deviation of the normal distribution (sigma), and (c) in the tail (tau) of the ex-Gaussian distribution. Thepresent experiments investigate whether the semantically based Stroop effect (which contrasts incongruent color-associatedwords with neutral controls) is seen in the three ex-Gaussian parameters. This analysis yielded a semantic Stroop effect in thearithmetic mean and mu, but no semantic Stroop effect was observed in tau. These data are consistent with the conclusion thatinterference associated with response competition on incongruent trials is absent in the semantic Stroop effect (at least in thetail of the distribution).

The role of main partnerships in shaping HIV transmission dynamics among men who have sex with men (MSM) has gained recognition in recent studies, but there is little evidence that existing definitions of partnership type are accurate or have consistent meaning for all men. Using data collected from 2011 to 2013 on 693 partnerships described by 193 Black and White MSM in Atlanta, GA, partnership attributes and risk behaviors were examined and compared by race, stratified in two ways: (1) by commonly used definitions of partnerships as "main" or "casual" and (2) by a new data-driven partnership typology identified through latent class analysis (LCA). Racial differences were analyzed using chi-square, Fisher's exact, and Wilcoxon-Mann-Whitney tests. Black participants were less likely to report condomless anal sex (CAS) within partnerships they labeled as main, yet they were also less likely to describe these partnerships as "primary" on a parallel question. In contrast, within strata defined by the LCA-derived typology, most partnership attributes were comparable and the likelihood of CAS was equivalent by race. These findings suggest that classification of partnerships as main or casual does not accurately capture the partnership patterns of MSM, resulting in differential misclassification by race. Future studies and interventions should refine and utilize more evidence-based typologies.