In contrast, it is not observed for more verbalizable
experiences such as the contents of spoken statements.
The boundary conditions associated with VO involve
both situation and individual difference variables. An
important individual difference variable is expertise,
with verbalization impairing performance when per-
ceptual expertise is high (e.g., when individuals have
been perceptually trained with a stimulus) and verbal
expertise is low (e.g., among individuals with high
verbal ability or those trained to describe a stimulus).
A variety of situation variables have been found to
mediate VO during the encoding, postencoding, and
retrieval phases. With respect to encoding, verbaliza-
tion is observed with faces of persons from one’s own
race but not with faces of those of other races (demon-
strating a role of perceptual expertise). With respect to
postencoding, extensive verbalization produces
greater VO than more modest descriptions. With
respect to retrieval, VO is more likely to be observed
when the distractors are highly similar than when they
are dissimilar (and thus more verbally distinguish-
able). VO is more likely to be observed for faces pre-
sented upright than inverted faces (suggesting a role
of holistic processing). Despite the prevalence of VO
across many domains, a number of researchers have
failed to replicate the phenomenon. However, a meta-
analysis including 29 studies and 2,018 participants
found a statistically significant overall effect, indicat-
ing that participants who verbalized a target were 1.27
times more likely than nonverbalizers to misidentify
the target. Furthermore, this meta-analysis also
revealed that verbalization effects are more likely to
be observed when (a) the verbalization instructions
induce detailed and elaborate descriptions and
(b) there is a minimal time delay between the verbal-
ization and the recognition test.
Currently, it is not entirely clear why VO occurs,
and there are three competing accounts proposed to
explain the phenomenon. The content accountasserts
that it is the precise contents of what is said during
verbalization that interferes with memory. In other
words, people create verbalizations that do not quite
match up with the original visual memory, thus inter-
fering with future recognition. The content account
fits well with the effect of expertise on VO (see above)
and helps explain why extensive verbalizations
(which tend to include more inaccuracies) are more
disruptive, but it fails to account for why many studies
have failed to show a connection between the quality
of verbal descriptions and recognition accuracy. Italso has trouble accounting for why describing one
face can interfere with the recognition of a different
face. According to the criterion shift account,verbal-
ization biases participants toward the target-“not-
present” option, leading to reduced recognition accu-
racy when the target is present. Although this account
potentially explains VO results in studies with “not-
present” options, it fails to account for the many times
in which VO has been observed in the absence of a
not-present option. Finally, according to the process
shift account,verbalization changes the individual’s
processing orientation from a more holistic strategy to
a more local one. If, as is often the case, faces are ini-
tially encoded holistically, the verbally induced feat-
ural processing strategy may lead to recognition
processes that are incommensurate with the manner in
which the face was originally encoded. A particular
strength of the processing account is that it does not
require a link between verbalization quality and
recognition accuracy, which as stated above, is often
not demonstrated. Although at present there is some
controversy regarding the relative merits of the con-
tent, criterion, and processing shift accounts of VO, it
seem likely that all three accounts have merit. Further
research is needed to determine when each one is
most likely to apply.
In summary, a large amount of research has shown
VO to be a pervasive effect across many types of visual
memory and other areas of perception. A recent meta-
analysis has shown VO to be a relatively small, but
reliable effect on memory. Furthermore, characteristics
of the verbalizer, the particulars of the description task,
and what occurs between viewing the original stimulus
and retrieval of this stimulus appear to play a role in
the strength of the VO effect. Although the exact
cause(s) of VO remain unclear, that the effect occurs
and that it can significantly effect eyewitness memory
is beyond dispute. From a practical perspective, the
modest size of VO effects combined with its tendency
to dissipate over time suggests that investigators
should not avoid soliciting verbal descriptions from
witnesses. However, investigators may want to avoid
asking participants to make identifications immedi-
ately after providing extensive verbal descriptions of a
perpetrator’s face or voice.Jason M. Chin and
Jonathan W. SchoolerSee alsoEyewitness Memory; Reconstructive MemoryVerbal Overshadowing and Eyewitness Identification——— 831V-Cutler (Encyc)-45463.qxd 11/18/2007 12:44 PM Page 831