Consequences of base time for redundant signals experiments

Abstract

We report analytical and computational investigations into the effects of base time on the diagnosticity of two popular theoretical tools in the redundant signals literature: (1) the race model inequality and (2) the capacity coefficient. We show analytically and without distributional assumptions that the presence of base time decreases the sensitivity of both of these measures to model violations. We further use simulations to investigate the statistical power model selection tools based on the race model inequality, both with and without base time. Base time decreases statistical power, and biases the race model test toward conservatism. The magnitude of this biasing effect increases as we increase the proportion of total reaction time variance contributed by base time. We marshal empirical evidence to suggest that the proportion of reaction time variance contributed by base time is relatively small, and that the effects of base time on the diagnosticity of our modelselection tools are therefore likely to be minor. However, uncertainty remains concerning the magnitude and even the definition of base time. Experimentalists should continue to be alert to situations in which base time may contribute a large proportion of the total reaction time variance.

Workload capacity spaces: A unified methodology for response time measures of efficiency as workload is varied

“…For example, in a group of participants who exhibited super capacity, the withinchannel processing rate for double targets was estimated as substantially higher than the single-target rate, meaning that each channel actually performed better when the other channel was activated. Base times, however, were almost identical and could not account for the observed super capacity, in complete agreement with Townsend and Honey's (2007) conclusion.…”

“…Interestingly, this is just the opposite of what occurs in OR designs (cf. Townsend & Honey, 2007). This reversed role of the base time can be of assistance in assessing the magnitude of its influence and its relative contribution in the OR vs. AND paradigms.…”

“…Nonetheless, Townsend and Honey (2007) recently proved that, when considering the base time component in RTs, the capacity coefficient and race model inequality both generate an underestimate of the processing capacity of a system. In other words, one may observe C OR (t) values below 1, where, in fact, the real capacity of the system is unlimited or even super.…”

“…In addition, Appendix 3 reports simulation results and considers the implications of base times in the OR and AND tasks. Townsend and Honey (2007) discussed their theoretical findings in OR paradigms with regard to the experimental literature and provisionally concluded that, for base times that appear to be in the ballpark of what has been estimated in the laboratory, inferences about performance through C OR (t) and the bounds would not be seriously damaged. In both the OR and AND paradigms, the magnitude of the variance of T 0 versus that of the processing times of interest will be the determining factor, as Townsend and Honey showed in the OR case.…”

Converging measures of workload capacity

“…However, in practice, the capacity coefficient may be confounded by differences in "base time" (i.e., the time to complete early sensory and response preparation and execution processes) and speed-accuracy trade-off between conditions contributing to C(t). Townsend and Honey (2007) investigated base time effects and concluded that they are unlikely to be problematic. 2 Similarly, the design used in the OR redundant-target task, where double-and single-target conditions are randomized within blocks of trials, makes confounding from speed-accuracy trade-off unlikely, since it is usually assumed that participants can change trade-off strategies only if they can anticipate upcoming conditions (Ratcliff, 1978).…”