Interresponse-time sensitivity during discrete-trial and free-operant concurrent variable-interval schedules.

Bell (1999) watched pigeons choose between two keys. Each key paid grain on its own variable-interval clock.

The birds worked in two set-ups: short discrete trials and long free-operant sessions. The author timed how long each bird waited between pecks.

The birds’ time since the last peck predicted where they pecked next. Only two pieces of data were needed: the pause just ended and the last side picked.

This simple two-part rule explained choice as well as older, more complex equations.

Yuwiler et al. (1992) said pigeons “match” reinforcement rates rather than “maximize” payoff. Bell (1999) agrees matching happens, but shows it is driven by the single pause before each peck.

Nevin (1969) first showed that after a reinforcer pigeons are less likely to switch keys. Bell (1999) adds that the length of the pause since the last peck sets up the next choice.

Katz et al. (2003) later changed the pay rates every few minutes and still saw matching. Their fast shifts fit the same pause-based rule Bell (1999) proposed.

If two timing variables guide choice in birds, your learners may also decide by “how long since I last did it” and “which option I just used.” Try watching the pause before a response; it may tell you which item, task, or place the client will pick next. Build teaching loops that reset that pause to keep the desired response active.