First published online September 9, 2005
Journal of Experimental Biology 208, 3463-3473 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01767
Variable rewards and discrimination ability in an insect herbivore: what and how does a hungry locust learn?
Spencer T. Behmer1,2,*,
Corlisa E. Belt2 and
Martin S. Shapiro3
1 Department of Entomology, Texas A&M University, College Station, TX
77843-2475, USA
2 Department of Zoology, University of Oxford, South Parks Road, Oxford OX1
3PS, UK
3 Department of Psychology, California State University-Fresno, Fresno, CA
93740-8019, USA
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Fig. 1. Diagram of the two-sided Y-maze. Moveable gates separate area X from areas
A and B. Gates also separate areas A and B from the removable arms.
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Fig. 2. Choice data, expressed as a proportion, for each of nine successive
choice-trials. Naïve locusts were allowed to choose between two coloured
arms (green or yellow), one containing four pieces of wheat, the other
containing one piece of wheat. A total of 12 locusts were observed, and for
each locust the colour/reward combination remained constant over the entire
experiment (six locusts had the high reward paired with green, while six had
the high reward paired with yellow). Data are also presented for the positive
rewards combined. The dotted line indicates indifference to the positive and
negative rewards.
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Fig. 3. The mean (± S.E.M.) natural log
latency of response for the positive and negative colours over the course of
training. Three measurements were recorded: (A) enter time, (B) approach time
and (C) exit time.
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Fig. 4. Choice data, expressed as a proportion, for each of 18 successive
choice-trials. Naïve locusts were allowed to choose between two scented
arms (lemon grass or peppermint), one containing four pieces of wheat, the
other containing one piece of wheat. A total of 12 locusts was observed, and
for each locust the odour/reward combination remained constant for the first
nine trials (six locusts had lemon grass paired with the high reward; six had
peppermint paired with the high reward). At the 10th trial, the odour/reward
combinations were reversed. Data are also presented for the positive rewards
combined. For choice-trials 10-18, choosing correctly would be indicated by
small values. The dotted line indicates indifference to the positive and
negative rewards.
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Fig. 5. The mean (± S.E.M.) natural log
latency of response for the positive and negative odours over the course of
training. At the 10th trial, the odour/reward combinations were reversed.
Three measurements were recorded: (A) enter time, (B) approach time and (C)
exit time.
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Fig. 6. Choice data, expressed as a proportion, for each of nine successive
choice-trials. Naïve locusts were allowed to choose between two scented
arms (lemon grass or peppermint), one containing p21:c21 food, the other
containing p7:c7 food (see the Methods and Results section for a full
description of these foods). A total of 12 locusts was observed, and for each
locust the odour/reward combination remained constant over the entire
experiment (six locusts had the high reward paired with green, while six had
the high reward paired with yellow). Data are also presented for the positive
rewards combined. The dotted line indicates indifference to the positive and
negative rewards.
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Fig. 7. The mean (± S.E.M.) natural log
latency of response for the positive and negative odours, in response to
synthetic foods, over the course of training. Three measurements were
recorded: (A) enter time, (B) approach time and (C) exit time.
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© The Company of Biologists Ltd 2005
