Academic journal article Attention, Perception and Psychophysics

Expectancy in Humans in Multisecond Peak-Interval Timing with Gaps

Academic journal article Attention, Perception and Psychophysics

Expectancy in Humans in Multisecond Peak-Interval Timing with Gaps

Article excerpt

In two experiments, the peak-interval procedure was used with humans to test effects related to gaps in multisecond timing. In Experiment 1, peak times of response distributions were shorter when the gap occurred later during the encoding of the criterion time to be reproduced, suggesting that gap expectancy shortened perceived durations. Peak times were also positively related to objective target durations. Spreads of response distributions were generally related to estimated durations. In Experiment 2, peak times were shortest when gaps were expected but did not occur, confirming that the shortening effect of gap expectancy is independent of the gap occurrence. High positive start-stop correlations and moderate positive peak-time-spread correlations showed strong memory variability, whereas low and negative start-spread correlations suggest small response-threshold variability. Correlations seemed not to be influenced by expectancy. Overall, the peak-interval procedure with gaps provided relevant information on similarities and differences in timing in humans and other animals.

Estimating time is a fundamental ability involved in numerous everyday activities such as using natural pauses in conversation or social interactions, practicing sports, playing musical instruments, or moving and pausing in a changing environment (Buhusi & Meck, 2005; Gibbon, Malapani, Dale, & Gallistel, 1997). Various sources of interference in human time estimation have been identified when concurrent tasks requiring attention and memory were performed with timing (Brown, 1997). The role of expectancy was specifically analyzed in recent studies, showing that a time interval was judged shorter when a stimulus or an interruption in timing was expected during the interval (Casini & Macar, 1997; Macar, 2002; Tremblay & Fortin, 2003).

Studies with animals, using a peak-interval (PI) procedure with gaps, suggest that mechanisms related to memory and attention may contribute to performance in animal timing (e.g., Buhusi & Meck, 2000, 2002, 2006a, 2006b, 2007; Buhusi, Perera, & Meck, 2005; Buhusi, Sasaki, & Meck, 2002; Cabeza de Vaca, Brown, & Hemmes, 1994). Gaps were also used in a time reproduction task with humans. In this task, participants are first trained to reproduce a target duration (e.g., 2 sec), and a stimulus (e.g., a tone) is presented during its reproduction. Then, in experimental trials, a gap in stimulus presentation defines a brief period during which timing must be interrupted. Gap location and duration are varied. In this task, humans consistently end the interval reproduction later when the gap occurs later, and the length of reproduced intervals appears to be proportional to the duration of gap expectancy. Longest intervals are reproduced when a gap is expected throughout the interval reproduction but never occurs (Fortin & Massé, 2000), which confirms that reproduced intervals are lengthened by gap expectancy. The objective of the present study was to examine whether such effects may be observed in humans, using a PI procedure with gaps, which provides information unavailable with a time reproduction method.

In duration reproduction, a single keypress terminates the interval. The time between the beginning and the end of the interval is an estimate of the remembered target duration. It is assumed that during the interval, the current estimate of the time elapsed since the beginning is compared with the memory representation of the target duration, so that the reproduction is terminated when the two values correspond. When a gap is expected, longer reproduced intervals result from time-sharing between estimating time, represented as accumulating temporal information, and monitoring for the gap signal, which requires attention. This perturbs the accumulation process, which also needs attention to operate. The amount of temporal information accumulated when a gap is expected will therefore be lower, so that more time will be needed to reach the subjective target duration-hence, longer reproduced intervals. …

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