Handbook of Psychology, Volume 4: Experimental Psychology

Conclusions 467

of perceptual manipulations such as changes in size, location,
direction of face, color, and illumination (e.g., Biederman &
Cooper, 1991a, 1991b, 1992; Cave, Bost, & Cobb, 1996;
Cooper, Schacter, Ballesteros, & Moore, 1992; Srinivas,
1996a). Some of these findings have been interpreted as evi-
dence that object identification is not sensitive to certain stim-
ulus attributes, and therefore priming is not affected by these
attributes. However, Srinivas (1996b) has shown that picture
priming can be sensitive to size in the context of study and test
tasks that required size judgment. This finding suggests that
repetition priming may be sensitive to the particular process-
ing demands of the tasks in which the stimuli appear, and may
not be a fixed indicator of the stimulus attributes germane to
perceptual processing in general. However, this issue has thus
far received little attention in the repetition-priming literature.

Purity of Repetition-Priming Measures

Despite the large body of evidence suggesting a distinction
between repetition priming and forms of explicit memory,
Perruchet and Baveux (1989) demonstrated that performance
on certain repetition-priming measures, such as word frag-
ment completion and perceptual clarification (participants
identified words that were embedded within a gradually dis-
appearing mask), was correlated with performance on explicit
memory tasks, whereas performance on other repetition-
priming measures, such as perceptual identification and ana-
gram solution, was not. On this basis, Perruchet and Baveux
made a distinction between two classes of repetition-priming
tasks. Some tasks may be successfully solved through the use
of systematic, controlled procedures (strategic tasks, which
may correlate with explicit memory performance). For other
tasks, however, the solution seems to pop out from a diffuse,
undirected exploration (nonstrategic tasks).
The observations made by Perruchet and Baveux (1989)
highlight an important issue in repetition-priming research:
To what extent does a particular measure of repetition prim-
ing reflect what it is intended to measure? Among measures
of perceptual repetition priming, for instance, most include at
least some conceptual component. It can be difficult to com-
pletely separate facilitation based on perceptual features from
facilitation based on meaning when the stimuli themselves
have both perceptual and semantic qualities. To control for
these effects, some researchers have chosen to use novel
stimuli to eliminate the possibility of semantic information
contributing to perceptual repetition-priming performance
(e.g., Musen & Treisman, 1990; Schacter et al., 1990a).
Likewise, some measures of repetition priming may be
open to the use of the same strategies used to make explicit
memory decisions. In some instances, the only distinction
between a measure of perceptual repetition priming and a

measure of explicit memory may be a change in the test in-

struction. For instance, stem completion and cued recall dif-

fer only in that participants in a stem completion task are

instructed to complete the stems with the first word that

comes to mind, rather than with a previously presented word.

Of course, this does not imply that participants are always

using explicit memory strategies to perform priming tasks,

but it does highlight some of the difficulties in establishing a

pure measure of repetition priming in a normal population.

Summary

As should be evident from this survey of repetition priming

research, one of the hallmark characteristics of repetition

priming is that it is robust. Repetition-priming effects have

been demonstrated in patients with neurological disorders

as well as in normal populations, and at a wide range of in-

tervals across the lifespan, using a vast array of different

measures. Although repetition priming research is still a rela-

tively new science, researchers have amassed a rich data

store of knowledge on the subject. Despite the fact that much

of what we know about repetition priming comes from re-

search designed to address the multiple-systems versus pro-

cessing debate, a focus on supporting one view over the other

may not be the most fruitful path toward achieving an under-

standing of the mechanisms that underlie repetition priming

and other memory phenomena. The more integrated perspec-

tive afforded by both views may allow for a more compre-

hensive understanding of these mechanisms.

CONCLUSIONS

In this chapter, we tried to provide an historical overview of

the major theoretical and empirical advances in our under-

standing of semantic memory, semantic priming, and repeti-

tion priming. Significant progress has been made on both the

theoretical and the empirical fronts in each domain.

Although the concept of semantic memory remains

heuristic, semantic memory is no longer a coherent domain

of inquiry, as nearly all of the phenomena originally associ-

ated with semantic memory, such as how word meanings are

mentally represented and how language is understood, have

become separate research endeavors. The most important

recent theoretical advances have been the development of

distributed network models and high-dimensional spatial

models of knowledge representation. A promising direction

for future research is to explore these models in more depth.

Another important target of future research is the connection

between perceptual systems and semantic representations.

This issue is fundamentally important, yet it has received