Wenger, M. J., & Gibson, B. S. (2004). Using Hazard Functions to Assess Changes in Processing Capacity in an Attentional Cuing Paradigm. Journal of Experimental Psychology: Human Perception and Performance, 30(4), 708-719.

Abstract:
Processing capacity-defined as the relative ability to perform mental work in a unit of time-is a critical construct in cognitive psychology and is central to theories of visual attention. The unambiguous use of the construct, experimentally and theoretically, has been hindered by both conceptual confusions and the use of measures that are at best only coarsely mapped to the construct. However, more than 25 years ago, J. T. Townsend and F. G. Ashby (1978) suggested that the hazard function on the response time (RT) distribution offered a number of conceptual advantages as a measure of capacity. The present study suggests that a set of statistical techniques, well-known outside the cognitive and perceptual literatures, offers the ability to perform hypothesis tests on RT-distribution hazard functions. These techniques are introduced, and their use is illustrated in application to data from the contingent attentional capture paradigm.

Note:
This paper is about the capacity measures by using Townsend’s approach. It is well-written and reviews a lot of details about the measurement.

Capacity is defined as the amount of work the observer is capable of performing within some unit of time.
Capacity may be non-causal (how much a system is capable of doing, or how effectively it can perform a task, in various experimental contextsà an aspect of system functioning that is affected by something else (such as stimulus organization) rather than being responsible for producing some result) or causal (aspect of capacity is affecting system functioning to produce a particular pattern of observable results)

They compared the using of mean RT with the using of overall processing time (they suggested the latter is better).
“Cumulating this instantaneous measure over the range of the RT distribution is thus readily interpretable in terms of how much work the observer was capable of doing in that experimental condition across all sampled responses at or before each value of t. Mean RT, in contrast, does not provide this information, giving only an expectation for how much time overall was required to complete the task. And the CDF gives only the unconditional probability that the task would be completed at or before some particular time.”
The hazard function may well describe the capacity. “It expresses a conditional probability—the likelihood of an observer completing the task in the next instant, given that the observer has not yet completed the task.”

They introduced the issue of ordering (complete/ partial ordering) in RT literature which is also related to the capacity measurement.
To examine if the RT from different conditions is ordered, two approaches are introduced. The fist one is graphic. To plot the ln{-ln[s(t)]} against the time (t) to see if there is any cross between different curves. If not, it is well ordered. The second method is to compute the Schoenfeld residual to see if all values are constant (beata coefficient = 0?). If it is, the distributions are ordered. (They introduced the proportional hazards model to analyze the RT data. It allowed us to compare two more hazard factions at once.)
(I think this part is the very crucial part in this paper!!)

Finally, fixed-effect partial likelihood model was used to test if the effect is significant in different conditions.