Academic journal article Perception and Psychophysics

Temporal Preparation Facilitates Perceptual Identification of Letters

Academic journal article Perception and Psychophysics

Temporal Preparation Facilitates Perceptual Identification of Letters

Article excerpt

Recent evidence has suggested that perceptual processing of single stimulus features improves when participants are temporally prepared for the occurrence of the stimuli. This study was conducted to investigate whether the benefit of temporal preparation generalizes to perceptual identification of more complex stimuli, such as letters. In three experiments, participants discriminated masked letters under high- and low-temporal-preparation conditions. Visual discrimination performance in all experiments improved when the participants were temporally prepared. Therefore, the present results support the notion that perception benefits from temporal preparation not only at the feature level, but also at subsequent levels at which feature information is integrated.

Participants respond especially quickly to a stimulus when the temporal occurrence of this stimulus can be anticipated (Woodrow, 1914). This benefit of temporal preparation on reaction time (RT) has been repeatedly demonstrated (Bevan, Hardesty, & Avant, 1965; Klemmer, 1956; Niemi & Näätänen, 1981; Teichner, 1954) and been shown to be a robust phenomenon. For example, the temporal preparation effect is obtained with visual as well as with auditory stimuli (Niemi & Lehtonen, 1982; Sanders & Wertheim, 1973), and also for cross-modal stimulus arrangements (Drazin, 1961; Müller-Gethmann, Ulrich, & Rinkenauer, 2003; Rodway, 2005). In addition, this effect is observed for simple as well as for choice responses (see, e.g., Simon & Slaviero, 1975) and thus is independent of particular response requirements. According to Niemi and Näätänen (1981), a warning signal reduces uncertainty about when an imperative stimulus will occur, which in turn promotes the temporal preparation of the response.

To improve understanding of the temporal preparation effect, several studies have aimed to localize the effect within the processing stream from perceptual input to the corresponding response (for reviews, see Hackley & Valle-Inclán, 2003; Müller-Gethmann et al., 2003). The results of different experimental approaches, however, have revealed different loci of the temporal preparation effect. Specifically, some authors (e.g., Los, Knol, & Boers, 2001, Los & Van Den Heuvel, 2001; Sanders, 1998) and studies employing the additive-factor method (Sternberg, 2001) have argued that temporal preparation does not operate at early perceptual stages (e.g., Frowein & Sanders, 1978; Niemi, 1979; Niemi & Lehtonen, 1982; Raab, Fehrer, & Hershenson, 1961), but instead shortens the duration of late motor processes (Sanders, 1980a, 1998; Spijkers, 1990).

This assumption seems to be supported by studies in which the effects of temporal preparation on the correlates of motor processes have been assessed. For example, studies of this type have investigated such measures as response force (Mattes & Ulrich, 1997), reflex amplitude (Brunia & van Boxtel, 2000), transcranially evoked motoric potentials (Hasbroucq, Kaneko, Akamatsu, & Possamai, 1999; Tandonnet, Burle, Vidal, & Hasbroucq, 2003, 2006), and the contingent negative variation (Loveless, 1973; Van der Lubbe, Los, Ja.kowski, & Verleger, 2004). All of these studies concluded that temporal preparation affects motor processes.

More recent studies, however, have challenged the notion that temporal preparation operates exclusively or primarily at a late motoric level. The first line of evidence for an earlier locus of the temporal preparation effect emerged from chronophysiological studies (Hackley, Schankin, Wohlschläger, & Wascher, 2007; Hackley & Valle-Inclán, 1998, 1999; Müller-Gethmann et al., 2003; Smulders, 1993) employing lateralized readiness potentials to bisect RTs into early and late portions. Contrary to the prevailing view, the results of these studies showed that a reduction of temporal uncertainty shortens the early but not the late portion of RT. …

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