The whale shark is an active feeder, targeting concentrations of plankton or fish.
(Hereafter, we refer to the high concentration feeders as blue and low concentration feeders as yellow for ease of explanation).
One way to demonstrate a negative incentive contrast of this kind is to show that after experiencing two unrewarded visits at high concentration feeders (e.g. blue), bumblebees are more likely to sample a low concentration feeder (e.g. yellow) than after experiencing a reward followed by a non-rewarded visit at blue feeders (Prediction 1).
In Colony 1, the proportion of non-rewarded visits (visits within the 10-s refill delay) at feeders with lower concentration (mean ± SD = 0.47 ± 0.10, N = 15 days) was the same as at feeders with higher concentration (mean ± SD = 0.48 ± 0.06, N = 15 days; paired t test: t(14) = −0.64, p = 0.53).
The response was calculated as the number of visits to higher concentration feeders divided by the total number of visits.
Over the two presentations of the same condition, discrimination strength was calculated as the number of visits to higher sugar concentration feeders divided by the total number of visits.
Finally, the lapse rate is a measure of the frequency of errors (in this case, visits to the low concentration feeders) due to distraction, motivational problems, and other factors of a non-perceptual nature.
They explained that as the temperature increases up to a certain level (i.e., 600 °C) porosity increases and concentration of feeder coal decreases but results in lower reactivity, with further increase in temperature.
However, every condition was presented twice on consecutive nights on which the feeder positions for each concentration were exchanged (Fig. 1, black and white feeders), as a control for positional biases.
All subsequent passages were performed by mechanical dissociation after treating colonies with collagenase II at 1 mg/ml, followed by plating cell clumps on feeder cells at a concentration of 1.25×10 cells/cm.
