502 Procedural Memory and Skill Acquisition
independent. Moreover, after finding that speed instructions
affect whether or not people learn to ignore irrelevant infor-
mation, Haider and Frensch (1999) argued that skill acquisi-
tion is neither passive nor “low-level,” but at least partly
under the influence of intention.
It seems obvious that knowing what to attend to will in-
crease the chance that the right events are experienced such
that useful instances are created, and that the allocation of at-
tention at encoding and retrieval determines to a large extent
both the nature of what is learned and the influence of previ-
ous experiences on performance in the present. There is,
however, much to be said, and even more to be learned, about
the interplay between intention and attention, and about how
much we learn without really intending it.
IMPLICIT LEARNING
Learning without intention, and without conscious awareness
of what is being learned, is a topic that has received much at-
tention in recent decades. Models of skill typically emphasize
early processing of task instructions and goal-directed learn-
ing, and paying attention to the correct elements in a task sit-
uation is considered crucial to eventual skilled performance.
The topic of this section is implicit learning(also referred to
asincidental learning), that is, learning without intention, or
the unintended by-product of experience with a task.
Consider a relatively simple task, that of pressing an as-
signed key whenever a stimulus appears at one of four partic-
ular locations on a screen. The instructions are simple: Press
the rightmost key when the rightmost stimulus appears, the
second key to the right for a stimulus in the corresponding lo-
cation, and so on. One aspect of performance in such a task is
that, despite the simplicity of the task, performance improves
as a function of practice. Reaction times become faster and
error rates lower (Dutta & Proctor, 1992; Proctor & Dutta,
1993), with improvements in accuracy and reaction time typ-
ically following a power function (Newell & Rosenbloom,
1981; see Figure 18.1 and the chapter by Proctor & Vu in this
volume). These improvements can be attributed to intentional
learning of key and stimulus locations and of the stimulus-
response associations. Performance can be considerably im-
proved if elements are repeated within the sequence of trials.
One sort of repetition is just that: A particular stimulus may
be repeated in two successive trials (see the chapter by
Proctor & Vu for a discussion of the basis of such repetition
effects). However, even when the repetition occurs across a
longer sequence of trials, benefits of repetition can occur.
Nissen and Bullemer (1987) provided practice with the
task described above, in which keys are pressed according to
the spatial location of targets. Within the sequence of trials,
certain stimuli were repeated (designating the positions from
left to right as A, B, C, and D, the repeating sequence was
D-B-C-A-C-B-D-C-B-A). People who practiced this serial
response time(SRT) task with the 10-element repeating
sequence showed vastly more improvement than those who
practiced the task with a random presentation of stimuli, even
though the participants were not informed that there was a re-
peating sequence or instructed to look for repetitions while
performing the task.Implicit Learning and AwarenessThe participants in Nissen and Bullemer’s (1987) study evi-
dently learned something (the repeating sequence) even
though they were not instructed to do so. Organizing and
making sense of the environment is, however, something that
comes naturally to most of us. The question is, then, whether
participants in Nissen and Bullemer’s study either con-
sciously looked for or somehow noticed that there was a
repeating sequence and used this explicit knowledge to im-
prove task performance. In order to separate intentional and
incidental learning in this task, and in order to assess the role
of awareness in the performance of the task, Nissen and
Bullemer asked participants whether they were aware of
any sequences in the stimuli. All of the participants in the
repeated-sequence condition reported being aware of the
sequence. Thus, awareness was coupled with the improve-
ment of performance for this group. In order to address the
question of whether awareness was necessary for the perfor-
mance benefit to occur, Nissen and Bullemer repeated the
experiment with a group of individuals characterized by a
profound amnesia that prevented them from recognizing and
recalling material to which they had been exposed: Korsakoff
patients. As predicted, the Korsakoff patients reported no
awareness of the repeating sequence. More interesting, their
performance showed a degree of learning of the sequence
comparable to that of controls (see Figure 18.2). This shows
that learning can and does occur without awareness.
Later work (Willingham, Nissen, & Bullemer, 1989)
showed that the degree of awareness of the sequence is cor-
related with performance for normal participants: People
who showed more awareness (as indexed by explicit recall of
the sequence) also showed more performance improvement.
However, when anticipatory responses (i.e., pressing the
response key before the next stimulus appeared) were elim-
inated from the analysis, the difference in performance
between those who reported full or partial knowledge of the
sequence and those who could evidence no explicit knowl-
edge was minimal.