Conclusions

In sum, the burgeoning geometry literature arose from the rotational error that rats in Cheng’s (1986) study made. The rats confused geometrically equivalent locations (e.g., diagonally opposite corners) that are associated with different featural cues such as brightnesses of walls or patterns on panels in the corners. Mammalian species reviewed make rotational errors systematically under some circumstances. That is, in some situations, rotational errors are found significantly more than other kinds of errors. With intact, undegraded featural cues, either a wall of a distinctive color or objects in the corners, birds and fish have not been found to make systematic rotational errors. When featural cues are degraded on tests (for example, by making all features the same color), pigeons sometimes make systematic rotational errors. Under at least some conditions, however, all species also learn to use featural cues, choosing a correct location more often statistically than a rotational error.

 

Currently, debate concerning 1) the nature of geometric cues encoded, and 2) the modularity of geometric encoding form current topics of research. The work reviewed all use domesticated species or at least animals living most of their lives in rectilinear indoor spaces. This applies to the humans, monkeys, rats, pigeons, chicks (although they had few days of life before being tested), and even the fish in aquaria. Cheng and Newcombe (2005) wondered what this experience with rectilinear spaces in development might contribute to the encoding of geometric and featural cues. Recent research has also spread to wild-caught birds who have had at least substantial experience outdoors in natural settings. Some interesting differences have already been found (Gray et al., in press), and perhaps more will be found (e.g., Kelly’s program of testing Clark’s nutcrackers in ‘geometry’ paradigms).