Homogeneous chains, heterogeneous chains, and delay of reinforcement.
Keep the response look the same across early chain links to keep the learner moving quickly.
01Research in Context
What this study did
The team built two kinds of response chains. In one, every link looked the same: a rat pressed the same lever three times. In the other, each link looked different: press, then pull, then bite.
They timed how fast the rats worked during the first link. The only thing that changed was whether the moves matched or not.
What they found
Rats ran the first link faster when every move matched. Same move, same muscles, more speed.
When the moves switched, the early link slowed. Different topographies weakened the chain before the food arrived.
How this fits with other research
McDowell et al. (2021) show that bigger, faster food boosts rate. Jason et al. (1985) add a new knob: keep the move the same and you also get more responses.
Ahlborn et al. (2008) found the same rule inside stimulus classes. One response form per class made new links stick. Together the papers say: uniform moves matter from simple chains to full equivalence networks.
Cividini-Motta et al. (2024) never mention chains, yet their advice fits: give the best reinforcer only for the final, independent form. Pair that with A et al.’s tip—keep earlier forms identical—and skill programs gain speed at both ends.
Why it matters
When you build a chain, repeat the same topography in every early link. Save the new move for the last link that earns the token or snack. You will see faster, steadier responding through the whole sequence.
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02At a glance
03Original abstract
Three pigeons responded on two-component chain schedules in which the required response topography in the initial and terminal links was similar (a homogeneous chain) or dissimilar (a heterogeneous chain). Key-peck responding in the initial link under a variable-interval 60-second (VI 60) schedule produced a terminal link in which, in different conditions, either key pecking or foot treadling was reinforced according to a VI 60 schedule. Multiple VI 60 VI 60 schedules, in which the responses required in the chain schedules were maintained by primary reinforcement in the two components, preceded and followed each type of chain. These multiple schedules were used to ensure that both responses occurred reliably prior to introducing the chain schedule. Key-peck response rates in the initial link of the chain consistently were higher during the homogeneous chain than during the heterogeneous chain. These results illustrate that intervening events during a period separating an operant response from primary reinforcement influence that operant, independently of the delay between the response and reinforcement.
Journal of the experimental analysis of behavior, 1985 · doi:10.1901/jeab.1985.44-337