Rhesus monkeys (Macaca mulatta) map number onto space

Abstract

Humans map number onto space. However, the origins of this association, and particularly the degree to which it depends upon cultural experience, are not fully understood. Here we provide the first demonstration of a number-space mapping in a non-human primate. We trained four adult male rhesus macaques (Macaca mulatta) to select the fourth position from the bottom of a five-element vertical array. Monkeys maintained a preference to choose the fourth position through changes in the appearance, location, and spacing of the vertical array. We next asked whether monkeys show a spatially-oriented number mapping by testing their responses to the same five-element stimulus array rotated ninety degrees into a horizontal line. In these horizontal probe trials, monkeys preferentially selected the fourth position from the left, but not the fourth position from the right. Our results indicate that rhesus macaques map number onto space, suggesting that the association between number and space in human cognition is not purely a result of cultural experience and instead has deep evolutionary roots.

Budgerigars and zebra finches differ in how they generalize in an artificial grammar learning experiment

“…For instance, when pigeons are trained to respond to sequences with an A-B-C-D structure (the letters depicting different image categories), they respond more quickly when they see new strings in which the category items are in the original ordinal position than when they see strings in which the category items are switched (e.g., A-C-B-D) (45,46). A similar mapping of items to positions in both string-discrimination and food-localization paradigms has been noted in several primate species (20,47,48). While the positional learning as observed in the zebra finches is thus not uncommon, the detailed memory for item positions that they demonstrate in the current experiment is impressive, as they kept track of item positions over a set of ten training strings.…”

Core mathematical abilities in infants

“…4, where the MNL can take the form of two types of number-space mappings). Still, future studies are needed to establish whether the mapping between numbers and different spatial positions is completely independent from cultural artifacts in humans: during the first months of life, infants are plausibly determined in their exploration of the space by their parents' own attentional biases, although evidence demonstrating that the mapping of number onto a left-to-right-oriented axis exists in nonhuman species (Drucker and Brannon, 2014;Rugani et al, 2010Rugani et al, , 2015 suggests that it is in fact biologically determined. Ongoing studies are investigating the presence of this oriented number-space mapping in human newborns.…”

Development of Spatial-Numerical Associations

“…Remarkably, the birds exhibited a clear preference to peck at the 4 th and 6 th location from the left , indicating a) an ability to approximately encode 4 and 6 items, and b) a preference for asymmetric encoding of the order of items starting with the left side of space. These results are not a quirk of the avian brain; monkeys given a similar task show a similar preference for encoding number starting with the left side of space (Drucker & Brannon, 2014), and chimpanzees trained to order the Arabic numerals 1–9 also show a spontaneous preference for 9 appearing on the right and 1 appearing on the left (Adachi, 2014). These findings are suggestive of a spontaneous and unlearned link between spatial extent and number, as well as spatial location and numeric order, although whether humans inherit these links is not addressed in these studies.…”