Numerical competence in an African gray parrot (Psittacus erithacus).

Abstract

An African gray parrot (Psittacus erithacus), Alex, trained to label vocally collections of 1-6 simultaneously presented homogeneous objects, correctly identified, without further training, quantities of targeted subsets in heterogeneous collections. For each test trial Alex was shown different collections of 4 groups of items that varied in 2 colors and 2 object categories (e.g., blue and red keys and trucks) and was asked to label the number of items uniquely defined by the conjunction of 1 color and 1 object category (e.g., "How many blue key?"). The collections were designed to provide maximal confounds (or distractions) and thus replicate the work of Trick and Pylyshyn (1989) on humans. Humans count rather than subitize under such conditions. Alex's results (83.3% overall accuracy) are therefore discussed in terms of their relation to human numerical competence, particularly with respect to counting. Several studies have shown that a wide range of vertebrates recognize numerical quantities (e.g., reviews in Boysen & Capaldi, 1992; Davis & Perusse, 1988). Such studies are also often proposed as a basis for cross-species comparisons of general cognitive processing abilities (

Enumeration of briefly presented items by the chimpanzee (Pan troglodytes) and humans (Homo sapiens)

“…Does she also use attentional processing when estimating a number greater than 5 (cf. Pepperberg, 1994)? Further examination is necessary to address these questions.…”

“…Some researchers argue that animals only show subitizing, a perceptual, automatic, preattentive process (Davis & Perrusse, 1988). Others have argued for more complex cognitive processes (Boysen & Berntson, 1989;Capaldi & Miller, 1988;Pepperberg, 1994).…”

“…Miller (1993) suggests that modifying the original meaning of these processes to explain the various types of results from animal experiments is not acceptable. To use response times as data, it is necessary to teach "numerals" to animals, a simple, human-like, but difficult task (Biro & Matsuzawa, 2001a, 2001bBoysen & Berntson, 1989;Ferster & Hammer, 1966;Matsuzawa, 1985;Matsuzawa, Asano, Kubota, & Murofushi, 1986;Matsuzawa, Itakura, & Tomonaga, 1991;Murofushi, 1997;Pepperberg, 1987Pepperberg, , 1994.…”

Numerical Matching Behavior by a Chimpanzee (Pan troglodytes): Subitizing and Analogue Magnitude Estimation

“…Only a few studies on counting by chimpanzees (Boysen, 1993;Boysen & Berntson, 1989;Boysen, Berntson, Shreyer, & Hannan, 1995;Rumbaugh, 1990;Rumbaugh & Washburn, 1993) and by an African grey parrot (Pepperberg, 1987(Pepperberg, , 1994 could be referred to as evidence that satisfies a one-to-one correspondence principle. In a review of the animal numerical competence literature, Davis and Perusse (1988) postulated that subitizing can account for much of the animal data.…”

Chimpanzee (Pan Troglodytes) Counting in a Computerized Testing Paradigm

“…Ferster (1964) taught two chimpanzees to match each of seven three-digit binary numbers to presented arrays. Matsuzawa (1985) conducted similar studies with a chimpanzee, as did Pepperberg (1987Pepperberg ( , 1994 with an African grey parrot. Boysen (1993) reviewed similar findings from her numerical experiments with chimpanzees that provided evidence that animals were able to learn and appropriately apply numerical labels to arrays of differing sizes and compositions.…”