Social learning trials were conducted over a 4-day period,
at the rate of five trials per day. The cages of the demonstrator
and the na¨ıve observer were placed on the floor, 40 cm
apart, and positioned so that they faced each other at a 45◦
angle. Before each trial, the inverted test tube was first presented
to the demonstrator, who rapidly removed the stopper
and released the seeds into its food dish. After the demonstrator
had fed for 10 s, a blind was placed between the two
cages to avoid social facilitation effects, and the test tube was
presented to the observer for a 1 min trial. If the observer
succeeded in removing the stopper within this 1 min period,
it received 0.5 g of mixed seeds delivered to its food dish via
a section of plastic tubing. The observers’ test tubes were
always empty to avoid rewarding accidental openings (e.g.
with the head or the back of the neck while trying to escape).
If the observer did not succeed, another demonstration-trial
cycle was performed 1 min later, up to a maximum of five
trials per day. We recorded the number of trials required by
each individual to learn the task as the measure of social
learning ability. If an individual did not learn to open the
test tube within the 20 trials, the ceiling value of 21 was
recorded