Academic journal article Perception and Psychophysics

Crossmodal Temporal Discrimination: Assessing the Predictions of a General Pacemaker-Counter Model

Academic journal article Perception and Psychophysics

Crossmodal Temporal Discrimination: Assessing the Predictions of a General Pacemaker-Counter Model

Article excerpt

In this study, an extended pacemaker-counter model was applied to crossmodal temporal discrimination. In three experiments, subjects discriminated between the durations of a constant standard stimulus and a variable comparison stimulus. In congruent trials, both stimuli were presented in the same sensory modality (i.e., both visual or both auditory), whereas in incongruent trials, each stimulus was presented in a different modality. The model accounts for the finding that temporal discrimination depends on the presentation order of the sensory modalities. Nevertheless, the model fails to explain why temporal discrimination was much better with congruent than with incongruent trials. The discussion considers possibilities to accommodate the model to this and other shortcomings.

(ProQuest Information and Learning: ... denotes formulae omitted.)

Time is an essential component of our mental life. Hence, it is not surprising that for many years, philosophers and psychologists have been intrigued by the question of how time enters into our experiences and thus shapes our cognitions (Roeckelein, 2000). For example, the great philosopher Immanuel Kant (1787/1998) argued that space and time are basic intuitions ("a priori Anschauungen") that structure our cognition. In addition, he believed that time involves a more subjective intuition than does space (see Boring, 1957). Thus, among other things, the study of time perception derives from Kant's proposal about time. The perception of time also attracted early psychophysicists (e.g., Mach, 1865; Vierordt, 1868) and has remained an active field of research in psychology up to the present day (see Grondin, 2001; Meek, 2003). More recently, time perception has become a major object of research in the field of the cognitive neurosciences (see Lewis & Miall, 2003; Nobre & O'Reilly, 2004).

The question of how humans perceive time, however, is still a matter of controversy (see Grondin, 2001). Nowadays, various theories exist about the mechanism(s) underlying time perception. Many share the core assumption of an internal clock based on neuronal counting (e.g., Allan & Kristofferson, 1974; Creelman, 1962; Gibbon, 1991; Grondin, 2003; Treisman, Faulkner, Naish, & Brogan, 1990). The main features of such an internal-clock mechanism are a pacemaker and an accumulator. The pacemaker generates pulses, and these are registered by the accumulator. The number of pulses counted by the accumulator during a certain physical time interval represents the perceived duration of this interval. This pacemaker-counter model (PCM) has been successfully applied to time-related behavior of humans (Bendixen, Grimm, & Schroger, 2005; Killeen & Taylor, 2000; Penney, Gibbon, & Meek, 2000; Rammsayer & Ulrich, 2001) and animals (Fetterman & Killeen, 1995; Gibbon, 1977).

The present study tests new predictions of PCM. More specifically, we generalized the model such that it can be applied to a crossmodal temporal discrimination task. In this task, subjects were asked to discriminate between the duration of a constant standard and the duration of a variable comparison stimulus. The sensory modalities of the standard and the comparison were either congruent or incongruent. In congruent trials, both the comparison and the standard stimulus were either auditory or visual-that is, auditory-auditory (a-a) or visual-visual (v-v)-whereas in incongruent trials, one stimulus was auditory and the other visual-that is, auditory-visual (a-v) or visual-auditory (v-a). As shown below, PCM makes intriguing predictions for this task. These predictions were assessed through the results of three experiments. In Experiments 1 and 2, the standard preceded the comparison, whereas in Experiment 3, the comparison preceded the standard.

Applying PCM to Crossmodal Temporal Discrimination

In this section, we extend a general version of the PCM for temporal discrimination (Rammsayer & Ulrich, 2001) to the more complicated situation in which the standard stimulus and the comparison stimulus differ in sensory modality. …

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