![]() ![]() ![]() Timing ability depends on there being a natural progression through chains of collateral responses, but if those should occur out of order, so too would temporal judgements. If true, this model would support only the lowest, nominal, form of timing: some collaterals are cues for one temporal judgement, other collaterals cues for other judgements, but the animals are neither required nor expected to have any sense of ‘beforeness’ or ‘betweeness’ or ‘afterness’. Another is the connectionist model of Broadbent and Church ( Church and Broadbent, 1990, 1991), which avoids counting by positing vector multiplication of banks of registers that are driven by a bank of synchronized pacemakers.Īnother response is the ‘behavioral’ theory of timing (BeT, Killeen and Fetterman, 1988 Machado, 1997) predicated on two assumptions: (a) temporal discriminations and productions are mediated by a pacemaker-counter system in which collateral behaviors function as the counter, enabling an organism to identify its location in time through its discriminations of ongoing activities and (b) transitions between classes of collateral activities are produced by pulses from a pacemaker whose period is proportional to the average interval between reinforcers. One response to the challenge is the seminal Scalar Expectancy Theory of Gibbon and Church ( Church et al., 1992 Gibbon and Church, 1992), which posits such counting as an intrinsic property of the counter. It remains a challenge to theories of timing to explain what it means for animals that can't count to count seconds. Meck (1997) provides a thoughtful analysis of the appropriate criteria for attributing numerical competency to animals in the light of their impressive-but inherently analog-performance in counting tasks. Some non-human animals can count ( Davis and Pérusse, 1988), but not very high, not very well, and they'd really rather not at all ( Breukelaar and Dalrymple-Alford, 1998). How do pigeons and turtles ( Lejeune and Wearden, 1991) use a counter if they can't count? They have less face validity for non-verbal organisms. Most theories of timing assume just such count-mediated timing, and their resulting models are germane to human temporal judgements ( Wearden, 1991). A minority of humans use visual imagery, such as watching the hands on an imagined clock ( Feynman and Leighton, 1988). This is true both for adults and for children over 6 years ( Wilkening et al., 1987). They count ‘thousands’, or ‘hippopotamuses’ or ‘Mississippis’ or foot-taps. When asked to time an interval, humans almost invariably count.
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