Leaving patches: effects of economy, deprivation, and session duration.
Long sessions alone make birds (and probably people) stick with one option longer, so shorten sessions before you call a choice a preference.
01Research in Context
What this study did
The team worked with pigeons in a patch-leaving game. Birds pecked a key in one patch, then walked a short or long path to a new patch.
They tested three things: closed versus open economy, food deprivation level, and short (40-min) versus long (120-min) sessions.
Each bird saw every condition, so the researchers could tease out what really made the birds stay longer in a patch.
What they found
Long sessions kept birds in patches almost twice as long, even when food was the same.
Closed economy and high deprivation added only a few extra seconds.
Session length, not food rules, was the big lever on patch time.
How this fits with other research
Martin et al. (1997) saw the same session-length twist in fixed-ratio work: long closed sessions pushed response rates up, short ones did not. Their earlier hint is now confirmed with patch time as the yardstick.
Martin et al. (1997) also tracked patch residence, but they changed prey arrival times instead of session length. Both studies show patch stays are controlled by timing variables, not just payoff.
Sutphin et al. (1998) found rats skipping costly patches by eating fewer, bigger meals. The pigeon data add that simply staying longer in one patch can also be a timing artifact, not a true preference.
Why it matters
If you use patch-leaving or choice tasks to gauge preference, clock the session length first. A long session can look like ‘commitment’ to a patch or task when it is really fatigue or time-on-task. Run brief sessions or rotate conditions within the same day to get a cleaner read on what your learner actually values.
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02At a glance
03Original abstract
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.
Journal of the experimental analysis of behavior, 1999 · doi:10.1901/jeab.1999.72-373