Learning simple and compound stimuli in a social lizard (Egernia stokesii).

We tested learning and behavioral flexibility in family-living gidgee skinks (Egernia stokesii) using a multistage visual discrimination task that included acquisition and reversal stages using simple and compound stimuli composed of black shapes superimposed on a colored background. We evaluated how lizards learn compound cues through a probe test. Lizards showed behavioral flexibility through reversal learning using simple stimuli (only color or shape). Our lizards used compound stimuli to learn a discrimination but had problems reversing and generalizing across novel compound stimuli. In the probe test, lizards chose the correct stimulus in a novel pairing with a distractor feature even without previous experience with compound stimuli. Our results suggest that some lizards are likely able to attend selectively to the relevant features of our compound stimuli while ignoring irrelevant features instead of using the configuration of a cue card as a whole to learn to discriminate between compound stimuli. We hope that our work will spark interest in further studies looking at how lizards (and reptiles in general) learn to solve visual discrimination problems.