450 Semantic Memory and Priming
assumed to be stored in a hierarchy determined by the logic
of class relations. A concept was stored closer to its immedi-
ate superordinates than to its more distant ones. For example,
robinwas represented as a bird,andbirdwas represented as
ananimal,butrobinwas not directly represented as an ani-
mal. The second assumption, which was referred to as “cog-
nitive economy” (Conrad, 1972), held that properties were
stored at the highest possible semantic level to which they ap-
plied. Continuing the example, featheredwould be stored
withbirdbut not with robin,because all birds are feathered,
whereascan flywould be stored with robinbut not with bird,
because robins can fly but not all birds can fly.
These assumptions generate two testable predictions:
First, member-category statements should be verified faster if
the subject is paired with an immediate superordinate, as in A
robin is a bird,than if the subject is paired with a more dis-
tant superordinate, as in A robin is an animal. Second, prop-
erty statements should be verified faster if the subject is
paired with a property stored with it, as in A bird has feathers,
than if the subject is paired with a property stored at a higher
semantic level, as in A bird eats. Both of these predictions
were confirmed (e.g., Collins & Quillian, 1969, 1972).
However, the hierarchical network model soon ran into
trouble. Conrad (1972) observed that Collins and Quillian
(1969) might have confounded hierarchical distance and as-
sociative strength. She argued, for example, that A bird has
feathersmight have been verified faster than A bird eatsbe-
causebirdandfeatheredare more highly associated than are
birdandeats, not because of a difference in network distance.
Conrad independently manipulated (a) the hierarchical dis-
tance between concepts and their properties, as determined
by the assumptions of hierarchical storage and cognitive
economy, and (b) the associative strength between concepts
and their properties, as measured by association norms. She
found that verification time decreased as associative strength
increased, but it was insensitive to hierarchical distance.
Rips, Shoben, and Smith (1973) also found that some mem-
ber-category statements involving immediate superordinates
took longer to verify than those involving distant superordi-
nates. For instance, A dog is a mammaltook longer to verify
thanA dog is an animal. This result conflicts directly with the
hierarchical storage assumption.
Subsequent studies (e.g., E. E. Smith et al., 1974) showed
that the critical determinant of decision times was the
strength of semantic or associative relation between the sub-
ject and the predicate. These studies also demonstrated that
typical exemplars of a category (e.g., robinofbird) were
verified faster than were atypical exemplars (e.g., chicken).
The hierarchical network model did not have mechanisms to
explain such findings.
False Statements and SimilarityAs described earlier, one of the predictions of the feature
comparison theory is that false statements containing similar
concepts should be more difficult to reject than false state-
ments containing dissimilar concepts. Holyoak and Glass
(1975) showed that this prediction was violated for two
kinds of statements. In one kind, similar statements ex-
pressed contradictions that were assumed to be directly rep-
resented in memory (e.g., All fruits are vegetables, Some
chairs are tables), whereas less similar statements did not
(e.g.,All fruits are flowers, Some chairs are beds). In the
other kind of statement, similar statements, but not dissimilar
ones, could be disconfirmed by the retrieval of a salient coun-
terexample (e.g., canaryforAll birds are robins). The impor-
tance of these findings is that they indicate that different
kinds of evidence can be used to make semantic decisions.
This conclusion does not bode well for models, such as the
feature comparison theory, in which a single source of infor-
mation is the basis of all semantic judgments.
In a comprehensive investigation of the processing of false
statements, Ratcliff and McKoon (1982) used a response-
signal procedure to trace the time course of processing. An im-
portant finding was that performance on category-member
statements (e.g.,A bird is a robin) was nonmonotonic: Early in
processing, there was an increasing tendency to respondtrue
to these false statements, but, later in processing, there was an
increasing tendency to respond correctly. This result indicates
that, later in processing, new information became available or
a second stage of processing was invoked. The nonmonoto-
nicity is problematic for the network models of semantic
memory, but it seems to offer support for feature comparison
theory. However, at all points in processing, including the very
earliest stages, subjects were more likely to respondtrueto
member-category statements (e.g.,A robin is a bird) than to
category-member statements, even though these statements
have equal amounts of overall feature overlap. This finding is
not consistent with feature-comparison theory.Contemporary Approaches to Semantic MemoryResearch on semantic memory flourished in the late 1960s
and 1970s but was already languishing in the early 1980s.
Cognitive psychologists did not lose interest in semantic
memory phenomena but, rather, migrated to more specialized
programs of research, such as word recognition (see chapter
by Rayner, Pollatsek, & Starr), language comprehension and
production (see chapters by Treiman, Clifton, & Antje and by
Butcher & Kintsch), and concepts and categories (see chapter
by Goldstone & Kersten). The models developed to account