Elliffe, D., & Davison, M. (2003).
Strict and random alternation in concurrent variable-interval schedules.
Journal of the Experimental Analysis of Behavior,
79, 65-85.
Six pigeons responded on pairs of concurrent variable-interval
schedules with, in different parts, four different arrangements
of alternation between schedules. Following a single
switching-key response, alternation was either strict or random,
and the alternative presented after a switch (the postswitch
alternative) was either signaled by the location of the switching
key or unsignaled. Generalized-matching analyses showed little
difference in behavior among the different alternation
arrangements, except the usual finding of lower sensitivity of
response allocation than time allocation was eliminated by
arranging random alternation. Patterns of interchangeover times
were similar for all arrangements except signaled random
alternation. Differences in behavior preceding the different
postswitch alternatives were found in the signaled random
alternation procedure. Preference was biased towards the color of
the signaled postswitch alternative and showed increased
sensitivity when the postswitch alternative was to be the one
with the higher reinforcer rate. Interchangeover times were
substantially shorter when the postswitch alternative was
signaled to be different from the current alternative than when
it was signaled to be the same. However, when separate reinforcer
ratios were calculated for the different postswitch alternatives,
those effects were eliminated or greatly reduced. We suggest
that, although behavior is indeed influenced by the postswitch
alternative, the mechanism is indirect. That is, the
distributions of reinforcers between alternatives obtained before
each postswitch alternative differ when those alternatives are
signaled and those distributions are discriminated, but the same
relations between choice and relative reinforcement hold
irrespective of which postswitch alternative is signaled.
Key words: choice, concurrent schedules,
generalized matching, interchangeover time,
strict alternation, random alternation, key peck, pigeons