Animal Cognition

, Volume 15, Issue 4, pp 711–717 | Cite as

Further evidence for addition and numerical competence by a Grey parrot (Psittacus erithacus)

  • Irene M. PepperbergEmail author
Short Communication


A Grey parrot (Psittacus erithacus), able to quantify sets of eight or fewer items (including heterogeneous subsets), to sum two sequentially presented sets of 0–6 items (up to 6), and to identify and serially order Arabic numerals (1–8), all by using English labels (Pepperberg in J Comp Psychol 108:36–44, 1994; J Comp Psychol 120:1–11, 2006a; J Comp Psychol 120:205–216, 2006b; Pepperberg and Carey submitted), was tested on addition of two Arabic numerals or three sequentially presented collections (e.g., of variously sized jelly beans or nuts). He was, without explicit training and in the absence of the previously viewed addends, asked, “How many total?” and required to answer with a vocal English number label. In a few trials on the Arabic numeral addition, he was also shown variously colored Arabic numerals while the addends were hidden and asked “What color number (is the) total?” Although his death precluded testing on all possible arrays, his accuracy was statistically significant and suggested addition abilities comparable with those of nonhuman primates.


Parrot cognition Parrot numerical competence Nonhuman addition Avian cognition 



This study was supported by many donors to The Alex Foundation. I thank Harrison’s Bird Diet and Fowl Play for food and treats, Avian Adventures for Alex’s cage, Carol D’Arezzo for Alex’s perch, and the several students who assisted in testing. This manuscript was written under the support of donors to The Alex Foundation (particularly Anita Keefe, the Michael Haas Foundation, and the Sterner family) and NSF grant BCS-0920878 (to Ken Nakayama). The study procedures comply with the current laws of the country under which they were performed.

Supplementary material

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Supplementary material 1 (DOC 28 kb)
10071_2012_470_MOESM2_ESM.doc (26 kb)
Supplementary material 2 (DOC 27 kb)


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  1. 1.Department of PsychologyHarvard UniversityCambridgeUSA

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