Abstract
The midsession reversal paradigm confronts an animal with a two-choice discrimination task where the reward contingencies are reversed at the midpoint of the session. Species react to the reversal with either win-stay/lose-shift, using local information of reinforcement, or reversal estimation, using global information, e.g. time, to estimate the point of reversal. Besides pigeons, only mammalian species were tested in this paradigm so far and analyses were conducted on pooled data, not considering possible individually different responses. We tested twelve kea parrots with a 40-trial midsession reversal test and additional shifted reversal tests with a variable point of reversal. Birds were tested in two groups on a touchscreen, with the discrimination task having either only visual or additional spatial information. We used Generalized Linear Mixed Models to control for individual differences when analysing the data. Our results demonstrate that kea can use win-stay/lose-shift independently of local information. The predictors group, session, and trial number as well as their interactions had a significant influence on the response. Furthermore, we discovered notable individual differences not only between birds but also between sessions of individual birds, including the ability to quite accurately estimate the reversal position in alternation to win-stay/lose-shift. Our findings of the kea’s quick and flexible responses contribute to the knowledge of diversity in avian cognitive abilities and emphasize the need to consider individuality as well as the limitation of pooling the data when analysing midsession reversal data.
Highlights
An animals’ environment is not necessarily stable over time
In the midsession reversal experiment, the visuo-spatial group showed about 90% correct choices before and after the reversal, whereby they made many errors in the first few trials after the reversal (Fig. 2)
As in the midsession reversal experiment, we found a clearly significant interaction between trial number, session number, and group (Table SI 10), whereby we found that the probability of errors decreased with trial number within sessions, that this effect got more pronounced over the course of sessions and so in the visuo-spatial group (Fig. 7)
Summary
An animals’ environment is not necessarily stable over time. Living in demanding and constantly changing environments may select for individuals with cognitive abilities that enable them to be successful even in variable situations (Milton 1981; Bond et al 2007; Shettleworth 2010). To avoid the memory influence, researchers adopted a midsession reversal paradigm (MSR), which tests the animal’s immediate response to the reversal of reinforcement contingencies at the midpoint of each session (Cook and Rosen 2010; Rayburn-Reeves et al 2013b). Kea have proved themselves as extremely flexible in behavioural and cognitive terms by quickly switching between different problem-solving strategies even after one has proved to be successful (Werdenich and Huber 2006) or by spontaneously innovating tool use when other attempts to reach encapsulated food failed (Auersperg et al 2011a, b) These aspects could possibly influence the responses in the task. Estimating these effects in the framework of hierarchical models allows one to estimate the amount of between- and within-individual variation in the strategy used
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