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Viktor Sarris, Petra Hauf, Marija Arlt; One- and two-dimensional psychophysics in humans and chickens: Size and color data. Journal of Vision 2001;1(3):364. doi: 10.1167/1.3.364.
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In several experiments the general assumption was tested that the chickens' psychophysical choice behavior is altered by context conditions similar to previous findings regarding human participants. In Experiment 1, the asymmetry (“anchoring”) of the training and test stimuli was investigated by means of a “two stimulus — two choice” paradigm by using various one-dimensional test series (cf. Sarris, BBS, 1994). All subjects (4 chickens and 20 humans) were trained and tested with cubes of different sizes. As predicted, the humans as well as the chickens showed systematic shifts of their behavioral choices depending on the extent of contextual test-asymmetry. Since most natural objects differ in more than only one stimulus dimension the experimental question was raised if there exist different choice-behavior strategies, when two or more psychophysical dimensions are used. Accordingly, the postdiscrimination-generalization paradigm was extended to a “four stimulus- two choice” paradigm, and the training was performed with two training pairs differing in size as well as in color (Experiment 2). The variable test-series asymmetry consisted of nine different sizes and two colors. Both animals and humans (6 chickens and 24 humans) showed different psychophysical size responses depending on the color used. These results correspond to other comparative data obtained in additional investigations (cf. Hauf & Sarris, 2001 this volume). Even though there is strong experimental evidence for the “relativism” of choice behavior in both humans and animals, the observed systematic differences suggest that probably distinct factors are responsible for one- versus two-dimensional choice behavior, thus pointing to the significance of basic perceptual as well as cognitive factors.
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