The ability to make inferences based on statistical information has so far been tested only in animals having large brains in relation to their body size, like primates and parrots. In a new study at Barcelona Zoo, researchers tested if giraffes (Giraffa camelopardalis), despite having a smaller relative brain size, can rely on relative frequencies to predict sampling outcomes.
The ability to make statistical inferences is considered a highly developed cognitive function and has only been tested in large-brained animals such as primates and keas (Nestor notabilis).
However, the statistical abilities of animals with proportionally smaller brains, such as giraffes, have not been tested.
In a new study, Dr. Federica Amici, a researcher at the University of Leipzig and the Max Planck Institute for Evolutionary Anthropology, and her colleagues presented two male and two female giraffes at Barcelona Zoo with a choice between two vegetable sticks held in a closed fist that had been drawn from transparent containers holding different proportions of preferred carrot sticks and less-preferred courgette (zucchini) sticks.
While the giraffes could see the amounts of the different vegetables in each container, they could not see which vegetable the authors selected and offered.
The different conditions included a container holding 20 carrots plus 100 courgette pieces versus one holding 100 carrots plus 20 courgette pieces, 20 carrots plus 100 courgette pieces versus 20 carrots plus four courgette pieces, and finally 57 carrots plus 63 courgette pieces versus 3 carrots and 63 courgette pieces.
The latter two conditions tested whether giraffes could assess the relative frequencies of the vegetables, rather than just the absolute numbers of each.
In at least 17 out of 20 trials, the giraffes were reliably able to select the container that was more likely to produce their favoured carrot sticks.
The researchers used control conditions to rule out whether the giraffe were…
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