Paying attention pays off: Kea improve in loose-string cooperation by attending to partner

Previous studies showed that kea are able to cooperate in experiments based on the loose-string paradigm, but success rates were low, except when tested in stable dyads. We trained kea with low success rates to attend to the handling of the string by a human partner. This vastly improved subsequent coordination during cooperation with kea partners. Furthermore, we tested the kea dyads with a delayed entry set-up (delays of 2, 4 or 6 s) and with two different lengths of string. Increasing length of delay and reducing string length had negative effects on the success rate. This suggests that a complete understanding of the actions was not present as the kea were not able to fully overcome factors that inhibit coordination. Lastly, we tested the three subjects showing the greatest ability to wait for the partner in a partner-choice paradigm: one subject in the central position could pull a loose string with one partner after another in the order it preferred. As a result, the second subjects had much longer waiting times than previously experienced. We could show that the central kea learned to visit both set-ups and that the second partner was able to wait for the partner to arrive before attempting to pull on the string, averaging twice as long as in the standard delay. Taken together, the results from this study highlight that cooperation in the loose-string paradigm is largely dependent on coordination of the subjects. While attention to the partner's actions greatly improved performance, the greater waiting times achieved in the final set-up also suggest that utilizing more ecologically relevant (subject is busy VS subject is held back) delays could further improve the performance of non-human subjects in the delayed loose-string paradigm.