Trends in Cognitive Sciences
ReviewDedicated and intrinsic models of time perception
Section snippets
Perceiving the passage of time
Cognition is dynamic, with our perceptions, actions and comprehension of the world unfolding over time. A generation ago, research on timing was limited, emphasizing the study of behaviors marked by temporal regularities [1]. More recently, a renaissance has taken hold in the study of time perception, with researchers addressing a broad range of temporal phenomena. Behavioral studies have revealed a host of puzzling effects in which our perception of time is far from veridical [2].
Dedicated models of temporal processing
Dedicated models of time perception are, at their core, modular. As vision scientists speak of dedicated mechanisms for color or motion perception, modular models of time perception entail some sort of specialized mechanism that represents the temporal relationship between events. The pacemaker-counter model is one example of a modular system [12]. These two components define a clock with an interval specified by the accumulation of inputs from a pacemaker. Spectral models of timing constitute
Intrinsic models of temporal processing
A spate of recent studies has promoted a more generic view of timing, which we will refer to as ‘intrinsic models’. Intrinsic models offer a radically different perspective on the perception of time. These models assume that there is no specialized brain system for representing temporal information, asserting that time is inherent in neural dynamics (Figure 1c,d). In one class of models, this property might be limited to neural regions that are capable of sustaining their activity in the
Evaluating the evidence for modality specificity in intrinsic timing
Some of the most compelling evidence for intrinsic timing comes from physiological studies that emphasize local representations that are, at least implicitly, modality specific. In one study neurons in the lateral inferior parietal region LIP were recorded during a visual duration discrimination task [5]. Two lights, the first of a fixed duration (e.g. 316 ms) and the second a variable duration, were presented at fixation. The animal judged the relative duration of the second by making a saccade
The role of nontemporal factors on perceived duration
Performance on time-perception tasks entails several component processes, many of which are not specific to time. These include attention, working memory and long-term or reference memory [55]. To date few studies of intrinsic timing have asked which of these processes are affected by training. Perceptual studies of generalization have reported that benefits are interval specific 56, 57, similar to the results observed by Meegen et al.[53]. Although this would rule out training effects related
Future directions
Following a modular paradigm, neuropsychological research generally has promoted models in which time is represented by dedicated neural systems. An appealing feature of these models is that they account for supramodal features of time perception and provide a principled basis for linking temporal processing in action, perception and cognition. By contrast, recent physiological and computational studies have highlighted how temporal information is reflected in the intrinsic dynamics of neural
Acknowledgements
The authors are grateful to Gerald Westheimer and Nola Klemfuss for their comments on this paper. This work was supported by grants from the National Institute of Health, NS30256, and National Science Foundation, BCS 0726685.
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