2003 IFA Congress: Montreal, Canada

Time Perception Investigations in Stuttering: Some Practical Issues

Michael Susca1, E .C. Healey2, and Thomas Carrell
1University of the Pacific, Department of Speech/Language Pathology, 3601 Pacific Avenue, Stockton, CA, 95211
2University of Nebraska, Department of Sp. Ed. & Comm. Dis., 253 Barkley Memorial Center, University of Nebraska-Lincoln; Lincoln, Nebraska 68583-0731

SUMMARY

Time perception is believed to be a fundamental precept underlying issues of time pressure and speech motor timing for people who stutter. Yet there is no sensory organ for time perception. This paper outlines preliminary considerations when investigating time perception, including perspectives and the time interval, time paradigms and estimation methods, as well as phenomena and stimuli. The article cautions that alterations in any of these issues may alter outcomes and outcome interpretations.

  1. Introduction
Having a “sense of time” may be a misnomer in that no sensory end-organ exists for time perception as end-organs exist with the other senses. The perception of time is therefore not a readily measurable entity, assuming it exists at all (see Gibson, 1975). Yet in the field of communication disorders, and in fluency disorders in particular, the perception of time plays a role in the adaptive regulation of oneself to effectively, smoothly, and continuously interact with a changing environment (Michon, 1985).

Time perception influences communication on many levels. It is observed in the rhythmic flow underlying appropriate turn-talking of verbal conversations, the timing of a joke’s punch line, and the responsive speed with which one answers questions seeking information or one’s name. Many people who stutter experience a disruption in the rhythmic flow of these and other conditions. Observable disruptions in the rhythmic flow may lead to disruptions in communication or communicative intent. Unobservable yet personally experienced disruptions in the rhythmic flow may lead to disruptions in the belief of a smooth and continuous communication experience. Thus, perceived disturbances in time, whether obvious or not, may lead to time pressure experiences as reactions to external or internal stimuli (Perkins, Kent, and Curlee, 1991), affecting the rhythmic flow of communication. However, time pressure is a concept much different from time perception. This distinction has not been consistently clear in past studies addressing these issues in fluency disorders.

For researchers contemplating time perception investigations, there are several issues that should be considered. Some issues include the orientation and scale of time represented, the perspective and time interval under consideration, the model upon which the investigation may be based, time estimation methods, the paradigm through which the investigation is conducted, and the phenomena and stimuli of the investigation. It is beyond the scope of this paper to address all these issues, and much has been written about them. Instead, the purpose of this paper is to alert time perception investigators to three important paired issues that may affect the design, method, and outcomes of time perception research in fluency disorders. The paired issues include perspectives and the time interval, time estimation paradigms and methods, and phenomena and stimuli parameters.

  1. Perspectives and the Time Interval
How time is perceived comes from the perspectives of simultaneity, succession, temporal order, duration, and temporal perspective. The time interval considered may range from a theoretical “perceptual moment” (Stroud, 1955), to brief, short, long, and very long intervals. Investigators’  findings may be influenced by the perspective and time interval considered.

The smallest moment of psychological time, called the psychological or perceptual moment (and in some cases a time quantum), has been hypothetically linked to alpha rhythms, or 100 ms/ cycle. However, the perceptual moment is a highly argued construct in the psychological literature, with only equivocal findings supporting it (Allport, 1968; Hylan, 1903; White, 1963). The unit is so small as to probably have limited general communicative significance. However, those investigating stuttering through neuro-imaging techniques and EEG studies may find such a time unit meaningful.

Simultaneity reflects a perspective where two stimuli or their onsets exist at the same instant. Discontinuity in the instant is discriminated in the smallest difference interval, the threshold of which differs in different perceptual systems. For example, in the visual system two binocularly presented stimuli with stimulus onset synchrony of 44 ms or less are perceived as a single stimulus, but at longer inter-stimulus intervals people perceived a flicker - or temporal discontinuity of the stimuli. In contrast, two auditory stimuli presented binaurally with stimulus onset asynchrony of 2 ms are perceived as successive (not a single stimulus) (Hirsh & Sherrick, 1961). In different sensory modalities there appears to be a small range of stimulus-onset asynchronies which are perceived as successive yet without clear temporal order. Thus, succession may be differentially determined by the sensory modality stimulated.

When a brief event or sequence of events last for a few seconds, people begin to experience the psychological or conscious present. The psychological present has been reported to be anywhere from a second (Boring, 1963) to 7 or 8 seconds (Michon, 1978) and sometimes longer. These are typical durations during which stuttering moments are experienced. It is during this brief interval that one can attend to time bi-directionally (James, 1890). The width of time has been reported as quite variable but it is through these time windows of the psychological present that awareness of event markers, event durations, intervals between events, ordering of events, and rhythm and flow of events may occur. It is through the perspectives of temporal order and duration that these event parameters may be assessed. Thus, in the case of a person who stutters, one may experience feelings of frustration or anxiety (Van Riper, 1972), deal with tension and fragmentation of the speech act (Bloodstein, 1993), or experience speech urgency (Starkweather & Givens-Ackerman, 1997) during the psychological present. It should be noted that perspectives of time investigations may include brief (1 to 30 seconds), short (30 seconds to several minutes), long (several minutes to several hours), and very long (days or weeks) intervals of time. The psychological literature is rampant with poorly agreed upon time interval definitions and such terms are used with specific relativity for various investigation purposes. Investigations of time perception need well-defined time intervals. Finally, time windows also provide a means for time tagging events and information in the broader temporal perspectives of past, present, and future. It seems that some level of information processing or temporal cognition, which may be conscious or unconscious, occurs. As such, attentional, memory, sequencing, and comparative processes may also be activated.

  1. Time Estimation Paradigms and Methods
There are two major time estimation paradigms (Block, 1974; Block & Zakay, 1997; Zakay, 1993). The first, called prospective or experienced duration, is one in which the participant has an a priori awareness that an estimation of elapsed time is required. The second, called retrospective or remembered duration, is one in which the participant is unaware that a time estimation of a task will be requested. Of course, retrospective paradigms are usually “one-shot” measures as once the person estimates a remembered duration, that person is alerted to time estimation as a task and may make prospective estimates on subsequent trials. Thus, the mixing of paradigms (or even time intervals) is likely to result in equivocal findings. For example, Barasch et al. (2000) asked fluent and non-fluent participants to engage in prospective measurements of empty and filled short durations (0.667, 2, and 12 second intervals) and retrospective measurements of a longer (filled) duration (30 minutes) (see below regarding filled and empty durations). From an ANOVA, they found a fluency main effect on the empty durations but not on the filled .667 second, two second, and 30 minute durations. Although time’s linearity has been demonstrated for short intervals (up to 30 seconds) it has not been equally demonstrated for long intervals (30 minutes). One may have difficulty interpreting investigations of time perception due to mixed paradigms, mixed time intervals, or mixed stimuli characteristics.

Additionally, there are significant considerations regarding prospective and retrospective paradigms (Zakay, 1990). A prospective estimate is primarily reliant on short term memory processes, a retrospective estimate is primarily reliant on long term memory processes. Time related processes are active during prospective tasks but passive during retrospective tasks. Time order errors, which occur when temporal judgments are influenced by the order of paired interval presentations (see Allan, 1979), are potentially negative (relatively shorter judgments made) on prospective tasks but positive (relatively longer judgments made) on retrospective tasks. Different cognitive and perceptual biases may also exist in the two paradigms, such as passivity versus activity of the participants, attentional resources available for the number of tasks, environmental tempo, induced time stress, and one’s occupation with the passage of time (Block, 1989; Block, 1990). Bower (1972) also noted “what the subject is thinking ‘about’ or the internal monologue” may influence remembered duration ( p.93.) Alterations in any of these variables may affect time estimation outcomes. Besides care in using estimation paradigms, care is also suggested in using estimation methods.

Several estimation methods are available for measuring perceptions of an objective duration (Allan, 1979; Bobko et al., 1977). For example, in the verbal estimation method a participant verbally estimates a target interval duration but in the reproduction of time method the participant does some activity to reproduce the time interval. In the time production method, the participant is asked to produce a predefined interval and in the comparison. method, the participant is asked to judge which of two presented intervals is longer. Although these four basic methods are recognized in the perception literature, more elaborate methods have been described (Allan, 1979). However, the method of estimation used may differentially influence the perception of an objective stimulus duration. Ezrati-Vinacour and Levin (2001) noted no significant differences existed between a group of stutterers and a group of fluent speakers on a prospective paradigm comparing production and reproduction estimation tasks in two listening and two speaking conditions. However, both groups tended to over-estimate during production estimates and under-estimate during reproduction estimates. Additionally, oral tasks were generally less accurately estimated than non-oral tasks. The psychological literature has shown wide inter- and intra-subject variability within and across various methods, leading Block (1990) to suggest that different methods may activate different time-related processes. Variability in time estimation methods may result in variability of measurements, as variability in stuttering measures results in different values.

  1. Phenomena and Stimuli Parameters
Two basic phenomena (empty and filled durations) and multiple stimulus parameters may also affect time perception experiences (Grondin, l993). For brief interval durations, multiple stimulus parameters may affect the perception of an interval duration. Specifically, a filled duration illusion, where time is perceived longer than it physically is, may occur when an interval is filled with various stimuli. In contrast, the same physically brief interval may be perceived as shorter when absent of stimuli. Multiple stimulus parameters may contribute to the filled duration illusion.

Filled duration illusions may be experienced with increases in stimuli number(Adams, 1977; Vroon, 1970), intensity (Goldstone et al., 1978), complexity, duration, changes in position (Poynter, 1989), movement (Brown, 1995), and size (Ornstein, 1969). The illusion has been reported in visual, auditory, and tactile modalities (Buffardi, 1971). Additionally, cognitive factors, such as number of interpretations of stimuli, processing speed of stimuli presentation, computational complexity, and the number of internal representations generated about a stimulus also contribute to relatively longer time estimates (Block, 1989; Burnside, 1971; Vittuli & Crimrnins, 1998; Vitulli & Shepard, 1996). Also, length, complexity, and familiarity of word stimuli may affect perceived durations (Avant & Lyman, 1975; Avant et al., 1975; Thomas & Weaver, 1975). Obviously, various cognitive experiences (confusion, “loss of control”, coping strategies), emotional reactions (anxiety, fear, frustration, guilt), and behavioral experiences (tensions and disruptions of breathing, phonating, articulating) during a stuttered moment (Bloodstein, 1995; Guitar, 1998; Manning, 2001) may contribute to distorted perceptions of time elapsing. Finally, retention of ‘brief durations in short term memory also variably affect interval duration perceptions, with recency of recall and information processing load contributing to the variability. That is, recent recall (under 4 seconds) may be more reliable than deferred recall (after 30 seconds). Likewise, less interpolative activity prior to recall may be more reliable than increased interpolative activity prior to recall. Clearly, stimulus parameters and how they are managed are important considerations for time perception investigations related to stuttering or fluency.

  1. Conclusion
Space limitations preclude an in depth assessment of the multiple practical issues which need to be considered when conducting time perception research. Although time perception has been noted as fundamental when assessing and treating fluency disorders, it has been a remarkably poorly researched area. Time perception differs from time pressure or temporal processing, the latter two being derived from the former. Therefore, investigators need to discriminate between time perception and time pressure, either of which might be mixed in error with temporal processing related to motor speech efforts. For those interested in time perception research in people who stutter, this essay has illustrated some -areas of general consideration and potential pitfalls that may alter investigation outcomes and interpretation of those outcomes.

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