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.
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With respect to noncompliance: In earlier studies (e.g., Pepperberg 1992; Pepperberg and Gordon 2005; Pepperberg and Lynn 2000), Alex, caring little for any reward, realized he could quickly finish a test no matter what he said. After learning his trainers would persevere, he realized he had to respond correctly for a test to end.
Wooden numerals—the initial stimuli when he was taught Arabic numerals–were always standardized with nontoxic paints for which Alex learned to use a specific color label; however, he chewed these numerals as his reward and they could not be replaced. We thus had to use magnetized plastic “refrigerator letters” for much of this study, and color errors occurred with these numerals. Paint that sticks to plastic is toxic, and because Alex is given the numeral to chew as his initial reward, could not be used. Note he did not always err on such items and would answer correctly when asked a second time, suggesting that the color clearly was on a boundary (e.g., if not yellow or red, it had to be orange).
Beran M (2011) Quantity judgments of auditory and visual stimuli by chimpanzees (Pan troglodytes). J Expt’l Psychol Anim Behav Proc. doi:10.1037/a0024965
Biro D, Matsuzawa T (2001) Use of numerical symbols by the chimpanzee (Pan troglodytes): cardinals, ordinals, and the introduction of zero. Anim Cogn 4:193–199
Bowmaker JK, Heath LA, Das D, Hunt DM (1994) Spectral sensitivity and opsin structure of avian rod and cone visual pigments. Invest Ophth Vis Sci 35:1708
Bowmaker JK, Heath LA, Wilkie SE, Das D, Hunt DM (1996) Middle-wave cone and rod visual pigments in birds: Spectral sensitivity and opsin structure. Invest Ophth Vis Sci 37:S804
Boysen ST (1993) Counting in chimpanzees: Nonhuman principles and emergent properties of number. In: Boysen ST, Capaldi EJ (eds) The development of numerical competence: animal and human models. Erlbaum, Hillsdale, pp 39–59
Boysen ST, Berntson GG (1989) Numerical competence in a chimpanzee (Pan troglodytes). J Comp Psychol 103:23–31
Boysen ST, Hallberg KI (2000) Primate numerical competence: Contributions toward understanding nonhuman cognition. Cognitive Sci 24:423–443
Boysen ST, Berntson GG, Shreyer TA, Quigley KS (1993) Processing of ordinality and transitivity by chimpanzees (Pan troglodytes). J Comp Psychol 107:208–215
Carey S (2009) The origin of concepts. New York, Oxford
Dehaene S (2011) The number sense: how the mind creates Mathematics, Chap 1. Oxford, New York, pp 3–29
Fuson K (1988) Children’s counting and concepts of number. Springer, New York
Matsuzawa T (1985) Use of numbers by a chimpanzee. Nature 315:57–59
Matsuzawa T, Itakura S, Tomonaga M (1991) Use of numbers by a chimpanzee: a further study. In: Ehara A, Kimura T, Takenaka O, Iwamoto M (eds) Primatology today. Elsevier, Amsterdam, pp 317–320
Mix K, Huttenlocher J, Levine SC (2002) Quantitative development in infancy and early childhood. New York, Oxford
Murofushi K (1997) Numerical matching behavior by a chimpanzee (Pan troglodytes): Subitizing and analogue magnitude estimation. Jpn Psychol Res 39:140–153
Pepperberg IM (1981) Functional vocalizations by an African Grey parrot (Psittacus erithacus). Z Tierpsychol 55:139–160
Pepperberg IM (1987) Evidence for conceptual quantitative abilities in the African Grey parrot: labeling of cardinal sets. Ethology 75:37–61
Pepperberg IM (1990) Cognition in an African Grey parrot (Psittacus erithacus): further evidence for comprehension of categories and labels. J Comp Psychol 104:42–51
Pepperberg IM (1992) Proficient performance of a conjunctive, recursive task by an African Grey parrot (Psittacus erithacus). J Comp Psychol 106:295–305
Pepperberg IM (1994) Evidence for numerical competence in an African Grey parrot (Psittacus erithacus). J Comp Psychol 108:36–44
Pepperberg IM (2006a) Grey parrot (Psittacus erithacus) numerical abilities: addition and further experiments on a zero-like concept. J Comp Psychol 120:1–11
Pepperberg IM (2006b) Ordinality and inferential abilities of a Grey parrot (Psittacus erithacus). J Comp Psychol 120:205–216
Pepperberg IM (2007) Grey parrots do not always “parrot”: Roles of imitation and phonological awareness in the creation of new labels from existing vocalizations. Lang Sci 29:1–13
Pepperberg IM, Carey S (submitted) Grey Parrot number acquisition: the inference of cardinal value from ordinal position on the numeral list
Pepperberg IM, Gordon JD (2005) Number comprehension by a Grey parrot (Psittacus erithacus), including a zero-like concept. J Comp Psychol 119:197–209
Pepperberg IM, Kozak FA (1986) Object permanence in the African Grey parrot (Psittacus erithacus). Anim Learn Behav 14:322–330
Pepperberg IM, Lynn SK (2000) Perceptual consciousness in Grey parrots. Amer Zool 40:393–401
Pepperberg IM, Wilkes SR (2004) Lack of referential vocal learning from LCD video by Grey parrots (Psittacus erithacus). Interact Stud 5:75–97
Pepperberg IM, Willner MR, Gravitz LB (1997) Development of Piagetian object permanence in a Grey parrot (Psittacus erithacus). J Comp Psychol 111:63–75
Pepperberg IM, Vicinay J, Cavanagh P (2008) The Müller-Lyer illusion is processed by a Grey parrot (Psittacus erithacus). Perception 37:765–781
Rugani R, Fontanari L, Simoni E, Regolin L, Vallortigara G (2009) Arithmetic in newborn chicks. Proc Roy Soc B 276:2451–2460
Shimomura T, Kumada T (2011) Spatial working memory load affects counting but not subitizing in enumeration. Atten Percept Psychophys 73:1694–1709
Spelke ES, Tsivkin S (2001) Language and number: a bilingual training study. Cognition 7:45–88
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.
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Pepperberg, I.M. Further evidence for addition and numerical competence by a Grey parrot (Psittacus erithacus). Anim Cogn 15, 711–717 (2012). https://doi.org/10.1007/s10071-012-0470-5
- Parrot cognition
- Parrot numerical competence
- Nonhuman addition
- Avian cognition