Temporal generalization and peak shift in humans

Abstract

Three experiments investigated temporal generalization in humans. In Experiment 1, a peak shift effect was produced when participants were given intradimensional discrimination training. In Experiment 2, after training with a standard S and generalization testing with an asymmetrical series of durations, generalization gradients moved toward the prevailing adaptation level. In Experiment 3, generalization gradients showed a central tendency shift and moved away from the S and toward the mean of the test series (of 11 stimulus durations) after participants received training with S and S durations that in one condition were the 2nd and 4th and in another condition were the 4th and 2nd stimuli in the series, respectively. The results were inconsistent with an absolute account of peak shift but were consistent with an adaptation level account of peak shift.

Learning-related shifts in generalization gradients for complex sounds

“…Bizo and McMahon (2007) recently reported that individuals trained to discriminate squares presented for different durations (e.g., 0.79 s versus 0.95 s) showed a peak shift effect along the dimension of duration. Russell and Kirkpatrick (2005) acquired similar results with rats.…”

“…In a classic example, pigeons trained on a wavelength discrimination between 550 nm light (S+) and 560 nm light (S−) responded most to shorter wavelengths such as 540 nm in a generalization test (Hanson, 1959). Such learning-related gradient shifts have been observed in bees (Lynn, Cnaani, & Papaj, 2005), horses (Dougherty & Lewis, 1991), rats, goldfish, guinea pigs, chickens, pigeons, and humans (reviewed by Purtle, 1973), and with various methods such as category learning (McLaren, Bennett, Guttman-Nahir, Kim, & Mackintosh, 1995; McLaren & Mackintosh, 2002; Wills & Mackintosh, 1998), varying distributions of test stimuli (Bizo & McMahon, 2007; Helson & Avant, 1967; Spetch, Cheng, & Clifford, 2004; Thomas & Bistey, 1964), and training with multiple S+ stimuli (Galizio & Baron, 1979; White & Thomas, 1979). The effect occurs for stimuli varying in brightness (Newlin et al, 1979; Thomas, Ost, & Thomas, 1960; White & Thomas, 1979; Thomas, Mood, Morrison.…”

“…When generalization tests are given after such training, subjects respond most not to S+, as one might expect, but to one of the unconditioned test stimuli. These shifts are often accompanied by a likewise shift in gradient mean and overall proportion of responding (Bizo & McMahon, 2007; Newlin, Rodgers, & Thomas, 1979; Thomas & Bistey, 1964; Thomas, Mood, Morrison, & Wiertelak, 1991). In a classic example, pigeons trained on a wavelength discrimination between 550 nm light (S+) and 560 nm light (S−) responded most to shorter wavelengths such as 540 nm in a generalization test (Hanson, 1959).…”

“…Consequently, use of the rule learned during training produces peak responding to a novel stimulus. Both of these explanations fail to explain some instances of peak shift (Bizo & McMahon, 2007, Cheng & Spetch, 2002; Doll & Thomas, 1964, Hanson, 1959; Lazareva, Wasserman, & Young, 2005; McLaren et al, 1995; McLaren & Mackintosh, 2002; Thomas, 1993; Thomas & Bistey, 1964; Thomas et al, 1991), but they have been able to explain other aspects of generalization (Helson, 1964; Spence, 1937; Thomas, 1993). For this reason, it is worthwhile to study peak shift in ways that control for the effects of inhibitory gradients and stimulus range.…”

Temporal Expectations Affect Retrospective Temporal Judgments: Evidence in Favour of Assimilation Effects

“…Adaptation-level theory has been applied to explaining temporal judgments, predominantly within prospective paradigms (e. g., [19,20,21]). However, the main principle of adaptation-level theory, namely that judgments of stimuli (durations) are affected by a frame of reference, is valid for both judgment paradigms.…”