Two Directions in a Search for Symmetry in Rats

Functional equivalence classes in rats: Repeated olfactory discrimination reversals and delayed stimulus probes

“…The idea that multiple exemplar training with symmetry relations might be necessary for animals to show emergent symmetry may seem a plausible account for the human–animal differences, as human children are naturally exposed to such training in infancy. However, a number of studies have failed to show consistent emergent symmetry even after providing multiple exemplar training in a variety of nonhuman species including chimpanzees (Dugdale & Lowe, 2000; Yamamoto & Asano, 1995), capuchin monkeys (Brino et al, 2014), pigeons (Gomez et al, 2014; Lionello‐DeNolf & Urcuioli, 2002; Navarro & Wasserman, 2020; Soares Filho et al, 2016; Velasco et al, 2010), and rats (Bruce et al, 2022).…”

“…This procedure has proven more robust with numerous successful replications in pigeons from the Urcuioli laboratory (e.g., Swisher & Urcuioli, 2015; see Urcuioli, 2015, for a review). However, use of these procedures does not appear to produce symmetry in rats (Bruce et al, 2022; Prichard et al, 2015) and, as yet, replications in other nonhuman species have not been attempted.…”