The number of each type of prey presentation made in sessions for all four experimental groups.

<p>The number of each type of prey presentation made in sessions for all four experimental groups.</p

The mean numbers (+/− SE) of mildly defended (circles) and moderately defended prey (squares) eaten in each session by birds in each of the experimental groups (N = 10 for all groups).

<p>The mean numbers (+/− SE) of mildly defended (circles) and moderately defended prey (squares) eaten in each session by birds in each of the experimental groups (N = 10 for all groups).</p

The proportion of eaten defended prey that were mildly defended in Sessions 3–8 and in the simultaneous choice session.

<p>Values over 0.5 show a preference for mildly over moderately defended prey. Birds marked with an asterisk (*) were labelled as discriminating birds.</p

The mean (+ SE) amount of quinine (mg) eaten per session in Sessions 3–8 in each of the experimental groups.

<p>Horizontal lines on the graph indicate the maximum amount of quinine available within a session for each group. The asterisk denotes a significantly lower ingestion of quinine in the Mild Defence group compared to the other groups. (N = 10 for all groups except the Non-Mimetic group where N = 9).</p

The mean (+ SE) number of mildly defended prey (light grey bars) and moderately defended prey (dark grey bars) eaten per session when birds had reached asymptote (sessions 3–8).

<p>In (a) data for all birds in all groups is included, and in (b) only data for the six discriminating birds in the Non-mimetic group is included (see text for details). Values that were significantly lower in the Non-Mimetic group compared to the Mild Defence and Moderate Defence group are marked with an asterisk. (N = 10 for all groups except the Non-Mimetic group where N = 9 in (a) and N = 6 in (b)).</p

Median viewing times for pairs of images presented in the image preference test.

<p>a) Monkey 1, b) Monkey 2, c) Monkey 3, and d) Monkey 4. Closed circles represent the 5^th and 95^th percentiles. Numbers on the x-axis refer to the total number of each type of image pairing the monkey was presented with during the preference testing.</p

The three conditions of the fluid + image reward task.

<p>The monkeys completed either a bar release (Monkeys 1 and 2) or fixation (Monkeys 3 and 4) before being presented with one of three conditions. Condition 1 (a) and Condition 2 (b) represent learning trials. In Condition 1 a saccade is made to an annulus to receive a preferred stimulus with no fluid. In Condition 2 the monkeys saccade to a cross to receive a fluid reward and a non-preferred image. In Condition 3, the monkeys choose between their rewards.</p

Average numbers of trials (±SEM) completed for the fluid only task (white bars) and the fluid + image reward task (all grey bar summed).

<p>Striped bars represent image rewards and solid bars represent fluid rewards. It should be noted that choices to view images were so rare that the bars are not visible in the figure. a) Monkey 1, b) Monkey 2, c) Monkey 3, d) Monkey 4 and e) all monkeys pooled.</p

Difference in the number of trials performed for the control task at the normal fluid allowance and after fluid allowance had been raised by 100 ml and the associated <i>t</i> test values.

<p>Difference in the number of trials performed for the control task at the normal fluid allowance and after fluid allowance had been raised by 100 ml and the associated <i>t</i> test values.</p

Examples of greyscale (a) and colour social images (b) and their matching control images (not to scale) which were 326 x 326 pixels and presented at 8.85 x 8.85 degrees of visual angle (dva).

<p>Examples of greyscale (a) and colour social images (b) and their matching control images (not to scale) which were 326 x 326 pixels and presented at 8.85 x 8.85 degrees of visual angle (dva).</p