Example learning curves for a slow and a fast learning bee.

<p>These curves illustrate how the performance of two bumble bee (<i>B. terrestris</i>) individuals change during the learning task. Black squares indicate the number of errors made by each bee in groups of 10 flower choices. Red curves, fitted to the empirical data using the formula: y = y0+Ae^−x/t<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090556#pone.0090556-Raine3" target="_blank">[24]</a>, illustrate how the performance of each bee changes during the task. Grey lines indicate the number of errors made by bees after 5, 50, and 100 flower choices. These three values were summed to generate a single measure of learning performance (Learning Performance Index: LPI) that accounted for the rate of change in performance (slope of the learning curve: t), the shape of the learning curve, and the saturation performance level (y0). Bee (A) is an example of a slower learner and has a higher LPI = 9.4, while bee (B) is an example of a fast learner and has a low LPI = 4.1.