Response-level probability effects on reaction time: now you see them, now you don't

Many reaction time (RT) experiments have tested for response-level probability effects. Their results have been mixed, which is surprising because psychophysiological studies provide clear evidence of motor-level changes associated with an anticipated response. A survey of the designs used in the RT studies reveals many potential problems that could conceal the effects of response probability. We report five new RT experiments testing for response-level probability effects with the most promising of the previous designs-that of Blackman ( 1972 )-and with new designs. Some of these experiments yield evidence of response-level probability effects, but others do not. It appears that response-level probability effects are present primarily in simple tasks with a strong emphasis on response preparation, possibly because participants only expend effort on response preparation in these tasks.     

Response time models of delta plots with negative-going slopes

Delta plots (DPs) graphically compare reaction time (RT) quantiles obtained under two experimental conditions. In some research areas (e.g., Simon effects), decreasing delta plots (nDPs) have consistently been found, indicating that the experimental effect is largest at low quantiles and decreases for higher quantiles. nDPs are unusual and intriguing: They imply that RT in the faster condition is more variable, a pattern predicted by few standard RT models. We describe and analyze five classes of well-established latency mechanisms that are consistent with nDPs--exhaustive processing models, correlated stage models, mixture models, cascade models, and parallel channels models--and discuss the implications of our analyses for the interpretation of DPs. DPs generally do not imply any specific processing model; therefore, it is more fruitful to start from a specific quantitative model and to compare the DP it predicts with empirical data.     

Beyond Knowledge Gaps: Examining Socioeconomic Differences in Response to Cancer News

This article tested a model, informed by the knowledge gap hypothesis, to predict information seeking about cancer immediately following news about the diagnosis or death from cancer of a national celebrity. I identified five celebrity news events and examined their impact using data from the 2005 Health Information National Trends Survey. News coverage about celebrity news events was more likely to promote information seeking among people with greater education than among those with less education. These differences were explained, at least in part, by the fact that highly educated people had greater health knowledge and community involvement than less‐educated people. These factors may contribute to widening socioeconomic gaps in prevention behaviors. I suggest strategies to address these gaps.