Molecular analyses of the principal components of response strength.
Response rate, latency, and probability are three read-outs of the same random process—model them together, not separately.
01Research in Context
What this study did
The authors built math models to explain three core facts: how often a response happens, how fast it starts, and how likely it is. They call the trio 'response strength' and treat each measure as a random draw from the same hidden process.
The paper is pure theory. No kids, no rats, no sessions. Just equations that show how a single stochastic engine can spit out rate, latency, and probability at the same time.
What they found
The model fits the curves. When the engine runs hot, responses come fast, start quickly, and almost always occur. When it runs cold, all three drop together.
The math gives you a ready-made ruler. You can plug in your session data and read off one number that tells you how 'strong' the behavior is right now.
How this fits with other research
Fox et al. (2001) ran the experiment first. They used real pigeons and PCA to prove that one hidden factor—response strength—links rate, latency, and persistence. The 2002 paper keeps the single-factor idea but swaps the stats: random processes instead of component scores.
Storm (2000) showed that Herrnstein’s k and R0 drift when schedule order changes. The new stochastic frame explains why: the underlying Poisson engine never sits still; its parameters wander within sessions.
Marr (1989) begged for Newton-style equations. This paper answers the call with concrete functions you can paste into Excel or R.
Why it matters
Next time your client’s rate jumps around, don’t average it away. Plot the session minute-by-minute and feed it into the refractory-Poisson sheet. If the latent strength estimate climbs, you know reinforcement is working even when raw counts look messy. One number, three windows, clearer decisions.
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02At a glance
03Original abstract
Killeen and Hall (2001) showed that a common factor called strength underlies the key dependent variables of response probability, latency, and rate, and that overall response rate is a good predictor of strength. In a search for the mechanisms that underlie those correlations, this article shows that (a) the probability of responding on a trial is a two-state Markov process; (b) latency and rate of responding can be described in terms of the probability and period of stochastic machines called clocked Bernoulli modules, and (c) one such machine, the refractory Poisson process, provides a functional relation between the probability of observing a response during any epoch and the rate of responding. This relation is one of proportionality at low rates and curvilinearity at higher rates.
Journal of the experimental analysis of behavior, 2002 · doi:10.1901/jeab.2002.78-127