A quantitative analysis of sensitivity to the conditioned reinforcing value of terminal-link stimuli in a concurrent-chains schedule.
Bright, salient terminal cues pull choice toward longer chained delays—use them when stretches exceed a few seconds.
01Research in Context
What this study did
Pigeons pecked two keys in a lab. Each key led to a different chain of delays before food.
The chains ended with colored lights. The colors varied in brightness and size. The study asked: do flashier lights make the chain more valuable?
What they found
Birds chose the shorter final delay more when the wait was long and the cue was bright.
The math fit a tweaked delay-reduction model. Salient cues added extra pull to the chain.
How this fits with other research
Henton (1972) saw no extra pull from chained lights at all. The birds picked equally whether the last link had a cue or not. The clash looks real, but the 1972 test kept delays short and cues dull. Omino (1993) stretched the delays and pumped up the lights, showing the cue effect only when both factors are big.
Hinson (1988) built the first hyperbolic-decay equation for these schedules. Omino (1993) bolted a salience knob onto that same equation, pushing the model one step farther.
Duncan et al. (1972) proved that extra chain links alone hurt value. Omino (1993) agrees and adds: if you must chain, make the last signal pop.
Why it matters
When you run token boards or chained schedules, track the terminal stimulus. A bigger, brighter token or final cue can salvage value lost to long waits. If the delay is short, the cue hardly matters—save your effort for stretches over a few seconds.
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02At a glance
03Original abstract
Pigeons were exposed to a concurrent-chains schedule in which a single variable-interval 30-s schedule was used in the initial links and fixed-time schedules were used in the terminal links. Three types of keylight conditions were used in the terminal links. In the first condition, different delays were associated with different keylight stimuli (cued condition). In the second condition, different delays were associated with the same stimulus, either a blackout (uncued blackout condition) or a white key (uncued white condition). Paired values of terminal-link fixed-time schedules differed by a constant ratio of 3:1, while the absolute value of delays was varied from 3 s to 54 s. The results showed that choice proportions for the shorter of two delays increased when the absolute size of the delays was increased for all keylight conditions. Further, the choice proportions for the shorter delay increased from the uncued blackout condition, to the uncued white condition, to the cued condition. A modified version of Fantino's (1969) delay-reduction model (expressed as a function relating the response ratio to the delay-reduction ratio) can be applied to these data by showing that sensitivity to delay reduction increased from the uncued blackout condition, to the uncued white condition, to the cued condition. Thus, the present study demonstrated that a modified version of the delay-reduction model can be used to assess quantitative differences in the terminal-link keylight condition in terms of sensitivity to delay reduction (i.e., the conditioned reinforcing value of the terminal-link keylight stimuli).
Journal of the experimental analysis of behavior, 1993 · doi:10.1901/jeab.1993.60-587