An eight-alternative concurrent schedule: foraging in a radial maze.
Different response measures tell different stories—nose pokes track reinforcement best, arm entries worst.
01Research in Context
What this study did
Researchers watched rats forage in a radial maze. The maze had eight arms. Each arm gave food on its own schedule.
The team recorded three things: nose pokes into the food cup, arm entries, and time spent in each arm. They added a short delay if the rat switched arms.
What they found
Nose pokes matched the food schedule best. Arm entries matched it worst. Time in arm was in the middle.
When the delay for switching was added, all measures became a little less sensitive to the food rate.
How this fits with other research
Shimp (1968) showed pigeons track the harmonic mean of food rates, not the simple average. F et al. now show rats do similar math, but only if you pick the right response.
HERRNSTEIN (1961) proved that pigeons can match their key pecks almost perfectly to food odds. The rat data echo this, again with nose pokes acting like key pecks.
Kelley et al. (2017) warn that free food can hurt other responses. F et al. add detail: the damage depends on which response you measure.
Why it matters
When you run concurrent schedules, pick one clear response to track. Nose pokes, button hits, or lever pulls give cleaner data than just walking into an area. If you must watch location, know it will understate the true sensitivity to reinforcement. Add change-over delays sparingly; they flatten the matching curve.
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02At a glance
03Original abstract
In two experiments conducted in an eight-arm radial maze, food pellets were delivered when a photocell beam was broken at the end of each arm via a nose poke, according to either fixed-interval or random-interval schedules of reinforcement, with each arm providing a different frequency of reinforcement. The behavior of rats exposed to these procedures was well described by the generalized matching law; that is, the relationships between log behavior ratios and log pellet ratios were approximated by linear functions. The slopes of these log-log functions, an index of sensitivity to reinforcement frequency, were greatest for nose pokes, intermediate for time spent in an arm, and least for arm entries. Similar results were obtained with both fixed-interval and random-interval schedules. Addition of a 10-s changeover delay in both experiments eliminated the slope differentials between nose pokes and time spent in an arm by reducing the slopes of the nose-poke functions. These results suggest that different aspects of foraging may be differentially sensitive to reinforcement frequency. With concurrent fixed-interval schedules, the degree of temporal control exerted by individual fixed-interval schedules was directly related to reinforcement frequency.
Journal of the experimental analysis of behavior, 1994 · doi:10.1901/jeab.1994.61-331