Academic journal article Canadian Journal of Experimental Psychology

Indirect Learning of Event Sequences: The Effects of Divided Attention and Stimulus Continuity

Academic journal article Canadian Journal of Experimental Psychology

Indirect Learning of Event Sequences: The Effects of Divided Attention and Stimulus Continuity

Article excerpt

Abstract In a serial reaction time (SRT) task, the learning curve is steeper when the stimuli are presented in a repeating sequential manner rather than in random order (Nissen & Bullemer, 1987). This is true even when subjects report being unaware of the presence of the repeating sequence. The present study examines the nature of this learning under conditions designed to reduce attentional resources and to disrupt the continuity of stimuli. In the first three experiments, subjects were trained in the SRT task, with or without the addition of a secondary tone counting task, and with repeating or non-repeating sequences. The results suggest that some sequence learning occurred despite the presence of a secondary task. Experiment 4 examined the extent of sequence learning when the inter-stimulus interval was varied between trials. The overall results suggest that despite reduced attentional allocation and discontinuous stimulus presentation, some sequence learning occurs. This result supports other work suggesting a dissociation between learning when measured explicitly, and when assessed through performance indicators.

There is growing evidence suggesting that subjects can learn complex tasks over time without being able to verbalize the rules and processes used during such learning. This dissociation between task performance and verbalizable knowledge has been demonstrated across a wide range of conditions including artificial grammar learning (see Reber, 1989, for a review), complex simulation tasks (Berry & Broadbent, 1984, 1988; Broadbent, Fitzgerald, & Broadbent, 1986; McGeorge & Burton, 1989; Stanley, Mathews, Buss, & Kotler-Cope, 1989), the detection of stimulus covariations (Lewicki, Czyzewska, & Hoffman, 1987; Lewicki, Hill, & Bizot, 1988), and the learning of event sequences (Nissen & Bullemer, 1987; Hartman, Knopman, & Nissen, 1989; Willingham, Nissen, & Bullemer, 1989). This has led some workers to argue that, at least for some tasks, learning can occur implicitly, in the absence of conscious awareness. There is much discussion as to what extent knowledge acquired implicitly is available to conscious awareness. Reber (1967), referring to artificial grammar learning, initially maintained that such knowledge was completely unavailable to conscious awareness. More recently he has modified this conclusion such that knowledge acquired from implicit processes is now considered knowledge that "in some raw fashion, is always ahead of the capability of its processor to explicate it" (Reber, 1989, p. 229).

In a serial reaction time (SRT) task designed to demonstrate implicit learning, Nissen and Bullemer (1987) showed subjects an asterisk in one of four designated positions horizontally along the bottom of a computer monitor. Subjects were required to respond to this stimulus by pushing as quickly as possible the designated key positioned directly below it. A correct response erased the stimulus and, after a 500 ms delay, a new stimulus appeared in one of the 3 other locations. In the repeating conditioning of the SRT task, the location of the stimuli appeared in a 10-trial continuously repeating sequence. Subjects were not informed of the presence of the sequence. In the random condition, subjects performed the same task but the stimuli appeared in random order. All subjects were trained over 800 trials and learning was inferred from a reduction in RT over trials.

At the conclusion of this task, subjects in the repeating condition were questioned about their knowledge of the sequence. On the basis of their responses they were divided into those who reported full explicit knowledge of the sequence, partial knowledge (able to specify at least 4 but fewer than 10 consecutive positions), and virtually no explicit knowledge (unable to specify more than 3 correct consecutive positions). Of primary interest was that even subjects who reported no explicit knowledge of the sequence were able to reduce RT over trials more so than subjects in the random group. …

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