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, 96 (1), 63-86

Reinforcement: Food Signals the Time and Location of Future Food

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Reinforcement: Food Signals the Time and Location of Future Food

Sarah Cowie et al. J Exp Anal Behav.

Abstract

It has long been understood that food deliveries may act as signals of future food location, and not only as strengtheners of prefood responding as the law of effect suggests. Recent research has taken this idea further--the main effect of food deliveries, or other "reinforcers", may be signaling rather than strengthening. The present experiment investigated the ability of food deliveries to signal food contingencies across time after food. In Phase 1, the next food delivery was always equally likely to be arranged for a left- or a right-key response. Conditions were arranged such that the next food delivery was likely to occur either sooner on the left (or right) key, or sooner on the just-productive (or not-just-productive) key. In Phase 2, similar contingencies were arranged, but the last-food location was signaled by a red keylight. Preference, measured in 2-s bins across interfood intervals, was jointly controlled by the likely time and location of the next food delivery. In Phase 1, when any food delivery signaled a likely sooner next food delivery on a particular key, postfood preference was strongly toward that key, and moved toward the other key across the interreinforcer interval. In other conditions in which food delivery on the two keys signaled different subsequent contingencies, postfood preference was less extreme, and quickly moved toward indifference. In Phase 2, in all three conditions, initial preference was strongly toward the likely-sooner food key, and moved to the other key across the interfood interval. In both phases, at a more extended level of analysis, sequences of same-key food deliveries caused a small increase in preference for the just-productive key, suggesting the presence of a "reinforcement effect", albeit one that was very small.

Keywords: choice; food reinforcement; pecking; pigeon; preference pulse; signaling.

Figures

Fig 1
Fig 1
Phase 1. A schematic diagram of the likely mean time to food on the left and right keys following a left- or right-key food delivery in Conditions 1 to 7, and 11. The mean interval for left- and right-key food deliveries, respectively, is shown by filled and open circles, respectively. Similar contingencies were arranged in Phase 2 (Conditions 8 to 10), but the key that produced the last food delivery was illuminated red (the other remained yellow) during the next interfood interval.
Fig 2
Fig 2
Phase 1. Mean log (L/R) obtained food ratio as a function of time since a left or right food delivery, in 2-s bins. Some data fell off the graphs.
Fig 3
Fig 3
Phase 1. Mean log (Left/Right) response ratios as a function of time since left and right food deliveries. Also shown is the extended-level preference averaged across the last 65 sessions of the condition separately for each prior reinforcer. Condition 3 was a replication of Condition 1, and Conditions 7 and 11 replicated Condition 5.
Fig 4
Fig 4
Phase 1. Mean log response ratio within interreinforcer intervals as a function of successive food deliveries from left and right keys. Sequences analyzed overlapped—that is, the data points plotted for an x value if 1 were from any sequence ending in a left or a right reinforcer; for x  =  2, the points were for any sequences ending in two left food deliveries, two right food deliveries, or left-right or right-left food deliveries.
Fig 5
Fig 5
Phase 2. Mean log (L/R) obtained food ratio as a function of time since a left or right food delivery, in 2-s bins. Some data fell off the graphs.
Fig 6
Fig 6
Phase 2. Mean log (Left/Right) response ratios as a function of time since left and right food deliveries. Also shown is the extended-level preference averaged across the last 65 sessions of the condition separately for each prior reinforcer.
Fig 7
Fig 7
Phase 2. Mean log response ratio within interreinforcer intervals as a function of successive food deliveries from left and right keys. See legend to Figure 4.
Fig 8
Fig 8
Calculated effects of left and right food deliveries across 60 s following those deliveries for selected Phase 1 conditions. See text for further explanation.
Fig A1
Fig A1
Phase 1, Condition 1. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig A2
Fig A2
Phase 1, Condition 2. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition. The initial point for Pigeon 22 fell off the graph.
Fig A3
Fig A3
Phase 1, Condition 3. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig A4
Fig A4
Phase 1, Condition 4. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition. Some initial points fell off the graphs.
Fig A5
Fig A5
Phase 1, Condition 5. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig A6
Fig A6
Phase 1, Condition 6. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig A7
Fig A7
Phase 1, Condition 7. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig A8
Fig A8
Phase 1, Condition 11. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig B1
Fig B1
Phase 2, Condition 8. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition. The initial point for Pugeon 22 fell off the graph.
Fig B2
Fig B2
Phase 2, Condition 9. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.
Fig B3
Fig B3
Phase 2, Condition 10. Log response ratio as a function of time since food, and mean extended-level preference, for Pigeons 21 to 26 according to the location of the last food delivery. The data are the last 65 sessions of this condition.

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