Biology Reference
In-Depth Information
acquisition and have less extinction than preforaging low-strain and
nectar-foraging wild-type bees. In the case of odors, an airstream with
a training odor (the CS) is blown on the antennae for a brief time before
the sugar solution is touched to the antenna (the US), followed by the
sugar reward presented to tip of the proboscis. At er very few trials,
the bees learn to extend their proboscis when presented with the
odor. Citral and carnation are typical odors used in olfactory associa-
tive learning.
Learning dif erences between pollen and nectar foragers and be-
tween preforaging-aged high- and low-strain bees can be attributed
to their dif erences in sensitivity to sugar. h is holds for both tactile
and olfactory learning. h e sucrose-response threshold of a bee pro-
vides a measure of her subjective value of the reward, as opposed to
the true value determined by the caloric content. Bees that are more
sensitive to lower concentrations subjectively value a reward of a su-
crose concentration more and, as a consequence, perform better in
associative learning. When bees are presented with equal subjective
rewards, they perform the same whether they are high- or low-strain
bees or pollen or nectar foragers. Equal subjective rewards are deter-
mined by presenting a concentration for a reward that is determined
by the sucrose-response threshold of the bee. For example, if two
bees vary in their response thresholds by one log unit (10-fold)—say,
one responds at 1 percent, the other at 10 percent—then the less re-
sponsive bee will be tested with a concentration 10 times greater
than that for the more responsive bee. In this case the less responsive
bee will be tested with 30 percent, the more responsive bee with 3
percent.
h e reward is evaluated at the proboscis. Ricarda Scheiner has shown
very nicely that even though the proboscis is less sensitive to sucrose than
are the antennae, the responses of the proboscis and the antennae are
strongly correlated. h is suggests that dif erences in sensitivity measured
at either point are consequences of dif erences in central nervous system
pro cessing.
