Elliffe, D., Jones, B. M., & Davison, M. (1999).
Leaving patches: Effects of economy, deprivation, and session duration.
Journal of the Experimental Analysis of Behavior,
72, 373-383.
Three pigeons pecked keys for food reinforcers in a laboratory
analogue of foraging in patches. Half the patches contained food
(were prey patches). In prey patches, pecks to one key
occasionally produced a reinforcer, followed by a fixed travel
time and then the start of a new patch. Pecks to another key were
exit responses, and immediately produced travel time and then a
new patch. Travel time was varied from 0.25 to 16 s at each of
three session durations: 1, 4, and 23.5 hr. This part of the
experiment arranged a closed economy, in that the only source of
food was reinforcers obtained in prey patches. In another part,
food deprivation was manipulated by varying postsession feeding
so as to maintain the subjects' body weights at percentages
ranging from 85% to 95% of their ad lib weights, in 1-hr sessions
with a travel time of 12 s. This was an open economy. Patch
residence time, defined as the time between the start of a patch
and an exit response, increased with increasing travel time, and
consistently exceeded times predicted by an optimal foraging
model, supporting previously published results. However,
residence times also increased with increasing session duration
and, in longer sessions, consistently exceeded previously
reported residence times in comparable open- economy conditions.
Residence times were not systematically affected by deprivation
levels. In sum, the results show that the long residence times
obtained in long closed-economy sessions should probably be
attributed to session duration rather than to economy or
deprivation. This conclusion is hard to reconcile with previous
interpretations of longer-than-optimal residence times but is
consistent with, in economic terms, a predicted shift in
consumption towards a preferred commodity when income is
increased.
Key words: patch residence time, travel time, closed economy,
session duration, food deprivation, key peck, pigeons