Semantic Priming 455over a network of units, and that semantically similar concepts
have similar patterns of activity. However, in these models
semantic priming is caused by incremental learning. Each pre-
sentation of a word causes all of the network connections par-
ticipating in recognition to be altered, so as to increase the
probability of producing the same response to the same input.
This learning facilitates processing of the word if it reappears,
but it also facilitates processing of words with similar repre-
sentations (e.g., a semantically related target). Learning decays
very slowly and is permanent unless undone by additional
learning. This class of models, unlike all other models of prim-
ing, predicts that semantic priming should occur over very long
lags between presentation of the prime and the target. Data rel-
evant to this prediction are reviewed in a subsequent section of
the chapter. Proximity may also play a role in these models, es-
pecially in explaining priming at short lags.
Major Issues and Findings
Neely (1991) provides the best comprehensive review of re-
search on semantic priming prior to 1991. Our review uses
Neely’s as a launching point. We focus on empirical issues
and findings that have turned out to be especially important
for testing models of semantic priming.
Automatic Versus Strategic Priming
Automatic processes are traditionally defined as those having
a quick onset, proceeding without intention or awareness,
and producing benefits but not costs. Strategic processes are
slower acting, require intention or awareness, and produce
both benefits and costs (e.g., Posner & Snyder, 1975).
Semantic priming almost certainly is not caused solely by
strategic processes (cf. C. A. Becker, 1980). Semantic prim-
ing occurs even when there is only one related prime-target
pair in the entire test list (Fischler, 1977a). In addition, at
short SOAs, semantic priming occurs between a category
name prime and exemplars of that category (e.g., body-leg)
even when subjects are told to expect members of a different
category (e.g., parts of buildings) to follow the prime (Neely,
1977). Findings such as these are difficult to reconcile with a
purely strategic account of priming. Semantic priming, how-
ever, is also not purely automatic. Two types of strategic
processes have been identified.
Under the appropriate conditions, semantic priming seems
to be affected by an expectancy process (e.g., C. A. Becker,
1980; Neely, 1977). Subjects use the prime to generate ex-
plicit candidates for the upcoming target or at least expect
primes to be followed by semantically related targets. Priming
can be amplified because of a speeding up on related trials or
a slowing on unrelated trials. Two factors seem to influence
the extent to which expectancy processes are used:1.The SOA between the prime and the target must be suffi-
ciently long to allow expectations to develop. A com-
monly used index of expectancy is inhibition, or longer
response latencies following unrelated primes than neutral
primes (e.g., a row of xs, or the words blankorready). The
reasoning is this: An expectancy process will yield an in-
congruent outcome on unrelated trials because the target is
unrelated to the prime. Responses should therefore be
slow in the unrelated condition relative to a condition in
which expectancies are not generated. A neutral prime
condition should provide such a baseline because neutral
primes are repeated many times in the test list and are ef-
fectively meaningless in the context of the experiment. It
is well documented that inhibition is small or nonexistent
for SOAs shorter than 300 ms (e.g., de Groot, 1984; den
Heyer, Briand, & Smith, 1985; Neely, 1977). In a direct
test of expectancy-based priming, Neely (1977) instructed
subjects to generate members of a specified category
when given a different category name as the prime; for ex-
ample, subjects were told to generate parts of the body in
response to the prime building(and building parts in re-
sponse to the prime body). Expectancy-based priming
occurred at a 700-ms but not at a 250-ms SOA.
2.The second factor that influences expectancy is the relat-
edness proportion (RP), which is typically defined as the
proportion of related trials out of all word prime–word
target trials (e.g., Neely, Keefe, & Ross, 1989). At long
SOAs, semantic priming and inhibition both increase in
magnitude as the proportion of related trials increases; at
short SOAs, the effects of RP are reduced or eliminated
(e.g., de Groot, 1984; den Heyer, Briand, & Dannenbring,
1983; Tweedy, Lapinski, & Schvaneveldt, 1977). Priming
in the naming task also increases with the RP (Keefe &
Neely, 1990), suggesting that naming is also influenced by
expectancy. It is unknown how low the RP must be to
eliminate expectancy. Low values of RP in published stud-
ies typically range from .10 to .33.The second type of strategic process is semantic matching
(e.g., de Groot, 1983; Forster, 1981; Neely, 1977; Neely et al.,
1989; Seidenberg, Waters, Sanders, & Langer, 1984). Under
the appropriate conditions, subjects seem to check for a rela-
tion between the target and the prime, responding quickly if
such a relation is detected, and slowly if no such relation is
detected. In the lexical decision task, the existence of a
semantic relation is always informative about the lexical sta-
tus of the target, as only word targets have related primes.