Making the strongest argument: Reply to Pepperberg (2015).

Abstract

Jaakkola (2014) argued that because the majority of studies of animals' understanding of invisible displacement did not adequately control for the use of alternative lower-level strategies, clear and solid evidence for a conceptual understanding of invisible displacement existed only for great apes. Pepperberg (2015) takes issue with this conclusion with respect to Grey parrots. While I agree that olfactory and social cueing may not be issues of concern for parrots, I reiterate the need for a study that adequately controls for associative learning before we can confidently claim that parrots understand invisible displacement.

Testing New Transposition Task Stimuli and Procedures with a Military Macaw (Ara militaris)

“…Pepperberg also disagreed with Jaakkola's stance that some of the studies involved associative learning rather than object permanence, but conceded that this is an issue on which it is difficult to reach agreement because almost any result could be seen as evidence of associative learning. Jaakkola (2015) agreed with Pepperberg (2015) that olfactory cues were not an issue for the studies involving parrots. She also agreed that social cues were probably not important, but did point out that the methods used, along with individual differences and learning, opened the door for the possibility of social cueing in the studies.…”

Causal and inferential reasoning in animals.

“…Several mammal and bird species are reported to have passed at least the single displacement task in this scale. There is controversy, however, on whether scientists took sufficient measures to guard against inadvertent experimenter-given cues and whether controls were conducted that help to disentangle associative learning and inferential explanations (Jaakkola, 2014(Jaakkola, , 2015Pepperberg, 2015). Control tasks that take care of some of these alternative accounts involve touching all the alternative hiding places without the possibility that the food was displaced to this location.…”

The “avoid the empty cup” hypothesis does not explain great apes’ (Gorilla gorilla, Pan paniscus, Pan troglodytes, Pongo abelii) responses in two three-cup one-item inference by exclusion tasks.

“…For instance, choosing the first or the last cup touched by the experimenter has commonly been evaluated as an alternative explanation to true object permanence in sequential invisible displacements (Collier-Baker & Suddendorf, 2006;De Blois et al, 1998). Although some of these heuristics seem to explain some of the results in some species (Collier-Baker et al, 2004;Deppe et al, 2009;Fedor et al, 2008), they do not explain other results (Collier-Baker & Suddendorf, 2006;Jaakkola, 2015;Pepperberg, 2015).…”