Abstract
Spectral stimuli form a physical continuum, which humans divide into discrete non-overlapping regions or categories that are designated by colour names. Little is known about whether non-verbal animals form categories on stimulus continua, but work in psychology and artificial intelligence provides models for stimulus generalization and categorization. We compare predictions of such models to the way poultry chicks (Gallus gallus) generalize to novel stimuli following appetitive training to either one or two colours. If the two training colours are (to human eyes) red and greenish-yellow or green and blue, chicks prefer intermediates, i.e. orange rather than red or yellow and turquoise rather than green or blue. The level of preference for intermediate colours implies that the chicks interpolate between the training stimuli. However, they do not extrapolate beyond the limits set by the training stimuli, at least for red and yellow training colours. Similarly, chicks trained to red and blue generalize to purple, but they do not generalize across grey after training to the complementary colours yellow and blue. These results are consistent with a modified version of a Bayesian model of generalization from multiple examples that was proposed by Shepard and show similarities to human colour categorization.
Full Text
The Full Text of this article is available as a PDF (192.2 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bowmaker J. K., Heath L. A., Wilkie S. E., Hunt D. M. Visual pigments and oil droplets from six classes of photoreceptor in the retinas of birds. Vision Res. 1997 Aug;37(16):2183–2194. doi: 10.1016/s0042-6989(97)00026-6. [DOI] [PubMed] [Google Scholar]
- Boynton R. M., Olson C. X. Salience of chromatic basic color terms confirmed by three measures. Vision Res. 1990;30(9):1311–1317. doi: 10.1016/0042-6989(90)90005-6. [DOI] [PubMed] [Google Scholar]
- Fried L. S., Holyoak K. J. Induction of category distributions: a framework for classification learning. J Exp Psychol Learn Mem Cogn. 1984 Apr;10(2):234–257. doi: 10.1037//0278-7393.10.2.234. [DOI] [PubMed] [Google Scholar]
- HANSON H. M. Effects of discrimination training on stimulus generalization. J Exp Psychol. 1959 Nov;58:321–334. doi: 10.1037/h0042606. [DOI] [PubMed] [Google Scholar]
- Johnstone T. Time for legalized distribution of illegal drugs? CMAJ. 1997 Nov 15;157(10):1345–1346. [PMC free article] [PubMed] [Google Scholar]
- Osorio D., Jones C. D., Vorobyev M. Accurate memory for colour but not pattern contrast in chicks. Curr Biol. 1999 Feb 25;9(4):199–202. doi: 10.1016/s0960-9822(99)80089-x. [DOI] [PubMed] [Google Scholar]
- Osorio D., Vorobyev M., Jones C. D. Colour vision of domestic chicks. J Exp Biol. 1999 Nov;202(Pt 21):2951–2959. doi: 10.1242/jeb.202.21.2951. [DOI] [PubMed] [Google Scholar]
- Shepard R. N. Toward a universal law of generalization for psychological science. Science. 1987 Sep 11;237(4820):1317–1323. doi: 10.1126/science.3629243. [DOI] [PubMed] [Google Scholar]
- Vorobyev M., Osorio D. Receptor noise as a determinant of colour thresholds. Proc Biol Sci. 1998 Mar 7;265(1394):351–358. doi: 10.1098/rspb.1998.0302. [DOI] [PMC free article] [PubMed] [Google Scholar]