466 Semantic Memory and Priming
simply a matter of emphasis. Shimamura points out that a
processing theory becomes a systems view when it attempts
to identify the neural circuitry associated with a process.
Likewise, a systems view becomes a processing view when it
attempts to identify the process that is subserved by some
neural circuitry.
Thus, it may make little theoretical difference whether
memory is characterized in terms of multiple brain systems or
cognitive processes. Ratcliff and McKoon (1996), however,
have pointed out that focusing on multiple memory systems has
movedmemoryto the foreground, and put into the background
an understanding of themechanismsthat mediate memory per-
formance. Likewise, the debate between systems and process-
ing views of memory has moved to the foreground research
focused on supporting one view over the other, rather than
using the broader perspective afforded by both views taken to-
gether to forward our understanding of memory phenomena.
Conceptual Versus Perceptual Priming
Primarily on the basis of the processing demands of a repeti-
tion-priming task, researchers have made a distinction be-
tween conceptual and perceptual repetition priming (e.g.,
Roediger & Blaxton, 1987; Roediger et al., 1989). Tasks that
involve analysis of stimulus meaning engage conceptual
processes, and tasks that involve analysis of stimulus form
engage perceptual processes.
Conceptual repetition priming is largely unaffected by
changes in the perceptual qualities of a stimulus between
study and test, and it is greater following conceptual elabora-
tion at study, such as encoding the meaning of study items.
Test tasks that have been used to measure conceptual repeti-
tion priming include category exemplar generation and an-
swering general knowledge trivia questions (e.g., Blaxton,
1989; Rappold & Hashtroudi, 1991). Although conceptual
processes are thought to also underlie performance on most
explicit memory tasks, dissociations between implicit-
conceptual and explicit-conceptual tasks have been reported
in normal and brain-damaged participants (e.g., Graf,
Shimamura, & Squire, 1985; McDermott & Roediger, 1994).
Although these results have been taken to suggest that sepa-
rable processes underlie conceptual implicit and explicit
memory, relatively little is known about the processes under-
lying conceptual priming (Vaidya et al., 1997).
Although the majority of research on perceptual repetition
priming has been in the visual domain, repetition prim-
ing has also been examined in the auditory domain. For
instance, Schacter, Church, and their colleagues (Church &
Schacter, 1994; Schacter, Church, & Treadwell, 1994;
Schacter, Church, & Bolton, 1995) undertook a systematic
investigation of repetition priming across changes in a variety
of auditory dimensions. Their participants listened to lists of
words recorded from a single speaker. At test, they attempted
to identify old and new words embedded in noise. Repetition
priming in this paradigm is evidenced by improved accuracy
for old words (Jackson & Morton, 1984). They found that
repetition priming was reduced (but not eliminated) by
changes in speaker, emotional or phrasal intonation, and fun-
damental frequency, but not by changes in volume (Church &
Schacter, 1994). Repetition priming was attributed to the
operation of an auditory word-form system specialized to
encode frequency information. Whether auditory repetition
priming is consistently sensitive to frequency information is
still uncertain; the effects of speaker are not observed in am-
nesic patients (Schacter et al., 1995) and are sometimes not
seen in normal participants (Jackson & Morton, 1984).Perceptual Specificity in Repetition PrimingAs mentioned previously, the majority of repetition priming
research has focused on perceptual repetition priming in the
visual modality. Common tests for visual perceptual rep-
etition priming include word-stem completion, fragment
completion (word and picture), lexical decision, perceptual
identification (word and picture), and picture naming. Gener-
ally, perceptual repetition priming at test is unaffected by
conceptual elaboration of study items (e.g., shallow vs. deep
processing) but is reduced when perceptual characteristics are
changed between study and test. For instance, changes in pic-
torial exemplar (e.g., from jet to biplane) can reduce per-
ceptual repetition priming, as can changes in symbolic form
(e.g., from picture to word) or presentation modality (e.g.,
from auditory to visual; e.g., Biederman & Cooper, 1991b;
Blaxton, 1989; Weldon, 1991).
Interestingly, Easton, Srinivas, and Greene (1997) demon-
strated robust repetition priming for words between visual and
haptic modalities (words were printed in raised characters that
were felt-like to the touch). Easton et al. speculated that vision
and haptics may both be adapted for spatial or object discrim-
ination and may share many of the same processing de-
mands and representational characteristics. Specifically, vi-
sion and haptics may share geometric representations, unlike
the phonological representations in audition. Thus, repetition
priming can occur across modalities if the modalities share
common representations (or representational characteristics),
but repetition priming is attenuated if the representations of a
stimulus in different modalities are also different (for addi-
tional discussion of visual-haptic interactions, see the chapter
by Klatzky & Lederman).
Despite the strong evidence for perceptual specificity in
priming, some studies have indicated that repetition priming
involving pictorial stimuli may be unaffected by a broad range