Collier, G., Johnson, D. F., & Mathis, C. (2002).
The currency of procurement cost.
Journal of the Experimental Analysis of Behavior,
78, 31-61.
As the number of instrumental responses required to procure
access to food is increased, animals decrease the frequency of
initiating meals and increase meal size, conserving total intake
while limiting the increase in the overall cost of feeding. In
two studies, one using wheel turns and one using bar presses as
the instrumental response, we asked whether freely feeding
laboratory rats measure cost according to the energy or the time
they expend. In each study we varied both the price (i.e., number
of wheel turns or bar presses) and the force required to make a
response (i.e., torque on the wheel or weight of the bar). Price
affected both procurement time (from the first to the last
procurement response) and procurement work, whereas torque and
bar weight affected work without altering time in most cases.
Meal patterns were altered by all manipulations of price, but
changes in torque and bar weight had little effect on meal
patterns, except in the conditions in which they altered
procurement time. These results suggest that time is a critical
currency of procurement cost in rats.
Key words: foraging cost, time, effort, meal patterns, wheel
running, bar pressing, rats