{"fact":"Crows may be more likely to participate in experiments and perform better if they are familiar with the experimenter.","context":"Our findings show that the birds participated more often in both tasks and were more successful in the exchange task when working with long-term experimenters than when working with short-term experimenters.","source":"Lara Cibulski; Claudia A.F. Wascher; Brigitte M. Weiß; Kurt Kotrschal, Familiarity with the experimenter influences the performance of Common ravens (Corvus corax) and Carrion crows (Corvus corone corone) in cognitive tasks, 10.1016/j.beproc.2013.11.013","index":107}