Are behaviors at one alternative in concurrent schedules independent of contingencies at the other alternative?
Apparent contrast in concurrent schedules can be a switch-rate artifact, not a change in preference.
01Research in Context
What this study did
MacDonall (2017) asked a simple question. Does changing the payoff on one key change how pigeons peck the other key?
He used two keys side by side. Both paid grain on variable-interval schedules. Then he turned off pay on one key. He watched if pecks on the still-paying key changed.
What they found
With strict rules, no clear contrast showed up. Birds kept pecking the paying key at the same pace.
With loose rules, it looked like contrast appeared. The difference came from how birds switched keys, not from true contrast.
How this fits with other research
Honig et al. (1988) had said contrast does happen when one key stops paying. MacDonall shows the earlier study missed a hidden switch rule. The two papers seem to clash, but the fight is over measurement details, not the birds.
White (1979) already showed that tougher switch rules cut hopping between keys. MacDonall uses that idea to explain why past "contrast" was mostly a switch-rate illusion.
Pear et al. (1971) saw contrast fade over days. MacDonall agrees: any brief bump you see will wash out once switching steadies.
Why it matters
If you run concurrent reinforcement programs, watch switch requirements before you claim contrast. A jump in one skill after you thin another may just reflect new switching patterns, not true behavioral change. Track change-overs, not just response rate, to spot the real effect.
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Count change-overs, not just responses, when you shift reinforcement on one alternative.
02At a glance
03Original abstract
Some have reported changing the schedule at one alternative of a concurrent schedule changed responding at the other alternative (Catania, 1969), which seems odd because no contingencies were changed there. When concurrent schedules are programmed using two schedules, one associated with each alternative that operate continuously, changing the schedule at one alternative also changes the switch schedule at the other alternative. Thus, changes in responding at the constant alternative could be due to the change in the switch schedule. To assess this possibility, six rats were exposed to a series of conditions that alternated between pairs of interval schedules at both alternatives and a pair of interval schedules at one, constant, alternative and a pair of extinction schedules at the other alternative. Comparing run lengths, visit durations and response rates at the constant alternative in the alternating conditions did not show consistent increases and decreases when a strict criterion for changes was used. Using a less stringent definition (any change in mean values) showed changes. The stay/switch analysis suggests it may be inaccurate to apply behavioral contrast to procedures that change from concurrent variable-interval variable-interval schedules to concurrent variable-interval extinction schedules because the contingencies in neither alternative are constant.
Journal of the Experimental Analysis of Behavior, 2017 · doi:10.1002/jeab.271