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First published online January 8, 2007
Journal of Experimental Biology 210, 269-277 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02656

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Parameters of variable reward distributions that affect risk sensitivity of honey bees

Tamar Drezner-Levy and Sharoni Shafir^*

B. Triwaks Bee Research Center, Department of Entomology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, 76100, Israel

View larger version (18K): [in this window] [in a new window]   Fig. 1. Generalization matrix between 1-octanol, benzyl acetate, eugenol and geranyl acetate. Each subject was conditioned with one of these odors and then tested with two of them (one of the test odors may have been the same as the conditioned odor). Thick horizontal bars represent median values for the duration of the proboscis extension response during the extinction (unrewarded) test trials. Error bars are the 25 and 75 percentiles (when the tested odor was different from the conditioned odor, these equaled 0 for all but one case). The number of subjects tested in each odor combination is noted.

View larger version (11K): [in this window] [in a new window]   Fig. 2. Mean (± s.e.m.) proportion choice of the constant reward in conditions of the risk-sensitivity experiment in which variability was in reward volume. For each condition, the values of the coefficient of variation (CV) of the variable reward distribution, whether it included zero rewards, the variance (µl2) and the skew (probability of the low reward) are listed. Distributions are positively skewed for skew >0.5. The broken line represents indifference. Different lowercase letters represent means that are significantly different from each other (P<0.05, Tukey's test). Numbers in the columns are sample sizes.

View larger version (7K): [in this window] [in a new window]   Fig. 3. Mean (± s.e.m.) proportion choice of the constant reward in conditions of the risk-sensitivity experiment in which variability was in reward concentration. For each condition, the values of the coefficient of variation (CV) of the variable reward distribution, whether it included zero rewards, the variance (%2) and the skew (probability of the low reward) are listed. Distributions are positively skewed for skew >0.5, and negatively skewed for skew <0.5. The broken line represents indifference. Different lowercase letters represent means that are significantly different from each other (P<0.05, Tukey's test). Numbers in the columns are sample sizes.

View larger version (19K): [in this window] [in a new window]   Fig. 4. The effects of the value of the low reward and distribution skew (probability of the low reward) on the coefficient of variation (CV). Calculations are for distributions with probability (P) of low reward value and probability (1-P) of high reward value, when mean reward equals 1 (lower gray surface) or 5 (upper transparent surface).