Observer Ratings of Personality
Robert R. McCrae
and
Alexander Weiss
National Institute on Aging, National Institutes of Health, DHHS
Baltimore, Maryland
Running head: OBSERVER RATINGS
Acknowledgement
This research was supported by the Intramural Research Program of the NIH, National
Institute on Aging.
Observer Ratings 2
Long before self-report personality scales were invented—as long ago as Theophrastus'
Characters, 319 B.C.E.—observers described personality traits in other people. Psychoanalysts
and psychiatrists developed formal languages for the description of personality traits in patients
that Block (1961) distilled into a common language in a set of Q-sort items. In psychology,
perhaps the first important use of observer ratings was Webb's 1915 study of trait ratings of
teacher trainees (Deary, 1996), and the discovery of the Five-Factor Model (FFM) of personality
was made through the analysis of eight observer rating studies (Tupes & Christal, 1961/1992).
Yet despite their historical importance, observer ratings are used far less often than self-reports
in personality assessment. This is unfortunate, because self-reports have well-known limitations,
and observer ratings can complement and supplement them. There is now a solid body of
evidence that ratings by informants well acquainted with the target provide reliable, stable, and
valid assessments of personality traits (e.g., Funder, Kolar, & Blackman, 1995; Riemann,
Angleitner, & Strelau, 1997).
There are several methods of obtaining observer-rating data. When members of a group
are asked to assess each other, a ranking technique is sometimes used, in which each group
member ranks every other member. Again, group members may nominate the single individual
who shows the highest level of a trait. Expert raters can be asked to complete a Q-sort to describe
targets (e.g., Lanning, 1994). However, in recent years most informant ratings have been
obtained by the use of questionnaires that parallel familiar self-report instruments. The Big Five
Inventory (BFI; Benet-Martínez & John, 1998) uses a format that can be applied to either selfreports or observer ratings; the Revised NEO Personality Inventory (NEO-PI-R; Costa &
McCrae, 1992) has parallel forms, with "I . . .," "He . . .," and "She . . ." phrasings. The firstperson version is called Form S, the third-person version Form R.
Observer ratings can be used in almost every context in which self-reports are normally
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used, but they are particularly valuable when (1) targets are not available to make self-reports;
(2) self-reports are untrustworthy; or (3) researchers wish to evaluate and improve the accuracy
of assessments by aggregating multiple raters (Hofstee, 1994). In this chapter we will focus on
ratings of personality (including traits, motives, temperaments, and so on), but the method can
also be used to assess psychopathology, moods, social attitudes, and many other psychological
constructs.
A Step-by-Step Guide
Selecting or developing the scale. A researcher or practitioner who wishes to assess a
personality construct needs some assessment instrument. For personality traits, standardized and
validated instruments should be the first choice. The BFI provides a quick assessment of the five
major personality factors, as does the short version of the NEO-PI-R, the NEO Five-Factor
Inventory (NEO-FFI; Costa & McCrae, 1992). The full, 240-item NEO-PI-R provides more
reliable measures of the factors, together with scores for 30 specific traits, or facets, that define
the factors. Goldberg's (1990) adjective scales have been used for observer ratings (e.g.,
Rubenzer, Faschingbauer, & Ones, 2000). The California Adult Q-Set (CAQ; Block, 1961) was
originally intended for quantifying expert ratings, but it has been adapted for lay use (Bem &
Funder, 1978) and can be scored in terms of the FFM (McCrae, Costa, & Busch, 1986).
There are several considerations in selecting among these instruments. The CAQ requires
the rater to sort items from least to most characteristic according to a fixed distribution. This
procedure eliminates certain response biases, but it is a lengthy and cognitively challenging task
relative to completing standard questionnaires. The full NEO-PI-R gives much more detailed
information than the NEO-FFI, but takes correspondingly longer to complete. The Goldberg
adjectives and the BFI are chiefly useful for research, because they do not offer normative
information. The NEO-FFI and NEO-PI-R have norms for observer ratings, and thus can be used
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in assessing individual cases as well as in research.
Observer ratings have generally been the preferred method of assessing temperament and
personality in children. Among the validated measures available are the EASI-III Temperament
Survey (Buss & Plomin, 1975), the Hierarchical Personality Inventory for Children (Mervielde
& De Fruyt, 1999), and the California Child Q-Set (Block, 1971), which can be scored for FFM
factors (John, Caspi, Robins, Moffitt, & Stouthamer-Loeber, 1994).
Because the FFM is a comprehensive model of personality traits, scales from these
instruments will be relevant in most applications. In some instances, however, the construct of
interest will be highly specialized (e.g., expectancy of occupational success) or only weakly
related to FFM dimensions (e.g., religiosity). In these cases, researchers have two options. The
first is to adapt an existing self-report scale for use by observers; the second is to develop a scale
de novo. The first option is clearly preferable; it saves time and effort, and there is now
considerable experience suggesting that observer rating adaptations of self-report instruments
maintain most of the psychometric properties of the original (e.g., McCrae et al., 2005). Research
employing a newly adapted observer rating scale should ideally include established measures
that can be used to provide validity evidence for the new scale.
If no established self-report measure is available, researchers can develop a new scale,
following the same procedures and standards that are used in the development of self-report
scales: Writing relevant items, piloting the scale, examining internal consistency and factor
structure, and gathering evidence of retest reliability and convergent and discriminant validity.
Observer rating scales are subject to biases and response sets much as self-report scales are, and
these biases must be considered in creating new scales. Acquiescent responding (McCrae,
Herbst, & Costa, 2001) is effectively neutralized by including approximately equal numbers of
positively- and negatively-keyed items. Evaluative bias in observer ratings is usually called a
Observer Ratings 5
halo effect, a tendency to attribute desirable or undesirable characteristics indiscriminately to a
target. Such biases can be controlled to some extent by phrasing items in objective terms, by
instructing raters to give a careful and honest description of the target, and by choosing raters
who are unbiased, or whose biases cancel each other out: One's true personality probably lies
somewhere between the descriptions given by one's best friend and one's worst enemy.
Selecting raters. The targets in an observer rating study are usually dictated by the
research question: If one wants to look for personality predictors of heart disease, the targets will
be coronary patients and controls. But there are several possibilities for selecting the raters.
Researchers who are interested in impression formation normally choose unacquainted
individuals and provide them with a controlled exposure to the target. For example, raters may
be shown a videotape of the target in a social interaction and asked to provide ratings (Funder &
Sneed, 1993). More commonly, researchers are interested in obtaining accurate assessments of
the target's personality, and choose raters who are already well-acquainted with the target:
spouses, co-workers, roommates, or friends.
There is some controversy about the effect of length of acquaintance on the accuracy of
ratings. Kenny (2004) goes so far as to say that "acquaintance is not as important in person
perception as generally thought" (p. 265). His conclusions are based chiefly on laboratory
studies, however, where short adjective scales are typically used and correlations across raters
are generally small (Mdn r = .15; Kenny, 2004, Table 1) and remain so after further exposure to
the target. Real life settings and questionnaire measures yield more evidence of an acquaintance
effect. For example, Kurtz and Sherker (2003) used the NEO-FFI on samples of college
roommates tested after two weeks and fifteen weeks and found median self-other agreement rose
from .27 to .43 across the five scales. It is likely, however, that a ceiling is reached fairly soon in
such settings, because self-peer agreement in a study that involved raters who had been
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acquainted with the target for up to 70 years showed a median correlation of only .41 (Costa &
McCrae, 1992).
These correlations are substantially higher than the '.3 barrier' once thought to
characterize the upper limit of personality scale validities, but they are also substantially less
than 1.0, which would indicate perfect concordance. Researchers who want higher correlations
have two choices: They can select intimate informants instead of merely well-acquainted
informants, or they can aggregate judgments from multiple raters. There is evidence from
American (Costa & McCrae, 1992) and Russian (McCrae et al., 2004) samples that spouse
ratings agree with self-reports more highly than do other informants' ratings (Mdns = .58 vs. .40),
presumably because people share more personal thoughts and feelings with spouses. In a Czech
study (McCrae et al., 2004), high self-other agreement (Mdn = .57) was found for ratings by
siblings, other relatives, and friends as well as spouses. Perhaps Czechs are generally more selfdisclosing than are Americans and Russians.
Gathering data from multiple raters of each target has two advantages. First, one can
assess interrater agreement, which gives a sense of the amount of confidence to be placed in the
ratings; it is particularly useful as evidence for the validity of new scales. Second, one can
aggregate (that is, average) across raters to improve the accuracy of the assessment. Agreement
between raters is called consensus in the literature on person perception, and it can in principle
arise from inaccurate shared stereotypes. But correlations between aggregated observer ratings
and self-reports are less likely to be due to stereotypes, and studies show that increasing the
number of raters increases self-other agreement, and thus, presumably, validity. Four raters per
target appears to be the practical maximum, although there are diminishing returns from any
more than two raters (McCrae & Costa, 1989). There has been no systematic research on the
optimal combination of raters; however, it would seem that the fullest portrait would be obtained
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by combining reports from raters acquainted with the target in different ways, for example, a
family member and a co-worker, or a same-sex friend and an opposite-sex friend.
Implementing the study. To this day, the bulk of personality research is conducted by
collecting self-report data from college students. The reason for this is simply convenience:
College students are at hand, and they can give informed consent and complete a questionnaire in
a single sitting. It is perfectly possible to conduct observer-rating studies in the same way, as
long as anonymous targets are used. For example, if one wished to know whether the association
between Openness to Experience and political preferences varied across the lifespan, one could
randomly assign students to think of a young, middle-aged, or old man or woman and provide
ratings of their personality and political beliefs (cf. McCrae et al., 2005).
But more commonly, the researcher wants to know about particular targets:
psychotherapy patients (see Bagby et al., 1998), job applicants, dating couples. In these
situations, the design is a bit more involved. It is first necessary to identify raters, who are
usually nominated by the target, and then in most cases it will be necessary to get informed
consent from both target and rater. In obtaining consent, it would be important to specify what
information from the observer rating, if any, would be divulged to the target: Some targets might
want to participate only if they will receive feedback; some raters might want to participate only
if their ratings were strictly confidential. In preparing instructions, it would be essential to make
it clear to the rater who the intended target was, and to include some check on this—for example,
by requiring the rater to provide the name and age of the target being rated. Beyond that, little
special attention is needed in the instructions: Raters are simply asked to describe the target by
judging the accuracy of personality items. People have very little difficulty with such a task.
Vazire (in press) advocated and illustrated the use of informant reports in Internet assessments.
In clinical practice, a psychotherapy patient may be asked to name a significant other
Observer Ratings 8
who could provide ratings of him or her; that person would then be contacted (perhaps by mail)
and asked to provide the ratings. (Written informed consent would not be required if the data
were used exclusively for clinical purposes, but mutual agreement among clinician, patient, and
rater would probably be needed in order to obtain valid and clinically useful ratings.)
In the 1980s, cross-observer agreement on personality traits was offered as evidence that
traits were veridical, and skeptics sometimes argued that the rater and target may have conspired
to give similar ratings. Usually instructions to avoid discussing the questionnaire with the target
are sufficient; if this is a serious concern, it may be necessary to gather data in a controlled
setting, with the rater physically separated from the target.
Research using couples often gathers self-reports and partner ratings from both partners.
This is a rich experimental design, because it allows the researcher to study such issues as
assortative mating (whether the two have similar personalities) and assumed similarity (whether
people tend to see others as they themselves are). But it also requires particular care in creating a
data file that clearly distinguishes the different method and target data, and that accurately
matches data from the two partners. Variable labels should reflect both the source and target of
the rating.
Examples of Observer Rating Research
Observer ratings can be used in almost any assessment of personality, but there are
several research circumstances in which they are particularly valuable. In some of these, their
value comes from their use in conjunction with self-reports. We provide three examples of these
applications, in personality research, in the interpretation of an individual case, and in latent trait
modeling. For other research problems, self-reports are not feasible, or even possible, and we
illustrate the use of observer ratings for assessing cognitively impaired adults, historical figures,
Observer Ratings 9
and chimpanzees. The use of observer ratings for the assessment of personality in children is
already widely practiced (e.g., Mervielde & De Fruyt, 1999).
Personality Research in the ABLSA
Some of the research that led to the prominence of the FFM was conducted in the 1980s
on members of the Augmented Baltimore Longitudinal Study of Aging (ABLSA). The BLSA
itself was begun in 1958 as a study of aging men; in 1978 women were added to the study, but at
a rather modest rate. Participants visited the Gerontology Research Center every one to two years
to complete a battery of biomedical and psychosocial tests. To increase the number of women in
the study, we augmented the BLSA by inviting the spouses of then-current BLSA members to
complete questionnaires at home (McCrae, 1982). Among the first data gathered from the
ABLSA in 1980 were self-reports on the NEO Inventory, a three-factor precursor of the NEOPI-R, and, a few months later, spouse ratings on a third-person version of the NEO Inventory. As
new versions of the instrument were developed that included scales for Agreeableness and
Conscientiousness, both Form S and Form R were readministered. Beginning in 1983, ABLSA
participants were asked to nominate peer raters, and these individuals in turn were asked to
complete Form R to describe the participant. The NEO-PI-R was administered to peer raters in
1990.
These data, in combination with the other psychological data collected in the BLSA and
ABLSA, led to several key findings:

Different observers agreed with each other and with self-reports at a level that
was both statistically significant and socially important, and the differences in
method made it unlikely that this was the result of artifacts. Personality traits
could be consensually validated, and thus the claim, prevalent in the 1970s, that
traits were mere cognitive fictions could be dismissed (McCrae, 1982).
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
When a self-report scale is correlated with a measure of social desirability, it may
mean that the scale is contaminated by the desire of the individual to present himor herself in a flattering light, or it may mean that the social desirability measure
is actually assessing genuine aspects of personality. Researchers routinely
presumed that the former interpretation was correct, and the dispute could not be
resolved if only self-reports were available. But significant correlations between
self-reported social desirability scales and observer ratings of personality could
not plausibly be attributed to a shared bias, and thus demonstrated that social
desirability scales assess more substance than style (McCrae & Costa, 1983).

Longitudinal studies of self-reports had consistently shown that individual
differences in personality traits are extremely stable in adults, with uncorrected
retest correlations near .80 over six- to ten-year intervals. But perhaps that simply
reflected the effects of a crystallized self-concept; people might be blind to
changes in their basic personality traits. If personality changed with age whereas
self-concept did not, self-reports should become increasingly inaccurate, and selfother agreement should be lower for old than for young targets. Observer rating
data showed that was not the case (McCrae & Costa, 1982), and longitudinal
stability coefficients in observer rating data were as high as in self-reports (Costa
& McCrae, 1988).

In principle, NEO-PI-R facet scale scores contain variance common to the five
factors, variance that is specific to the facet, and error. But unless there is
substantial specific variance, there is no need to assess facets; all personality traits
would simply be combinations of the five factors. It was possible to separate the
specific variance from the common variance by partialling out the factor scores,
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but against what criteria could one validate the residuals? Residuals from observer
ratings of the same facets were the natural choice, and correlations of the residuals
from the two methods in fact demonstrated the consensual validation of specific
variance in NEO-PI-R facet scales (McCrae & Costa, 1992).

The wish that we could "see oursels as ithers see us" (in Burns' language) is based
on the widespread belief that there are noticeably different public and private
selves. Hogan and Hogan (1992) referred to the former as reputation and believed
that the private self, available to introspection, must show a different structure of
personality. But the same FFM is found in self-reports and observer ratings
(Ostendorf & Angleitner, 2004), and agreement among different observers is not
systematically higher than agreement between self and other (McCrae & Costa,
1989). The distinction between public and private selves is thus in some sense an
illusion; there is no perfect consensus on our public self that we could hope to see,
and our self-reports are not based on some direct intuition of our inner nature, but
on self-observations that substantially overlap with what others observe.

The essence of good science is replication, and multimethod replications are
powerful because they reduce the possibility that findings are due to some artifact
of a particular method. In ABLSA studies, we showed that self-reports on the
NEO-PI-R were related to psychological well-being, interpersonal traits, Jungian
types, and ways of coping. All of these findings were replicated when spouse or
peer ratings were used as the measure of personality (Costa & McCrae, 1992).
Interpreting a Case Study: Madeline G
Costa and Piedmont (2003) reported a study of Madeline G, a flamboyant Native
American lawyer who volunteered to be a case study for a variety of personality assessors
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(Wiggins, 2003). She completed Form S of the NEO-PI-R, and her common-law husband
completed Form R to describe her.
Consistent with the general impression that she was a volatile and forceful character,
Madeline G's responses consisted almost exclusively of strongly disagree (33.8%) or strongly
agree (48.8%), and the resulting profile was correspondingly extreme: Four of the five domains
and 25 of the 30 facets were in the "Very Low" or "Very High" range. Such a profile is
statistically very unusual, and in isolation it would have been difficult to know whether it was
meaningful or merely an artifact of extreme responding. A comparison with Form R was
therefore more than usually informative in this case. Although not as extreme, her husband's
descriptions agreed in direction with her self-reports for three factors and 19 facets, suggesting
that her self-reports were exaggerated but not meaningless.
It is possible to assess the degree of agreement between two personality profiles (for
example, Madeline G's self-report and her husband's rating of her), although all the currentlyused metrics have limitations. As Cattell pointed out in 1949, simple Pearson correlations are
problematic because they reflect only the similarity of shape of the profile, not similarity of
level. Cattell's proposed alternative, rp, takes into account the difference between profile
elements, but not the extremeness of the trait. When Madeline G scores T = 16 on Agreeableness
whereas her husband places her at T = 4 (where T-scores have a mean of 50 and standard
deviation of 10), there is more than a standard deviation difference between the scores—yet both
depict her as profoundly antagonistic (recall that she was a lawyer). McCrae (1993) proposed a
different metric, the coefficient of profile agreement, rpa, that is sensitive to both the difference
between corresponding profile elements and the extremeness of the average score.
The computer-generated Interpretive Report (Costa & McCrae, 1992; Costa, McCrae, &
PAR Staff, 1994) for the NEO-PI-R calculates this quantity, and shows in the case of Madeline
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G that agreement is .95, which is very good compared to agreement between most married
couples. The high value is found in spite of major disagreements between the two sources on
some factors and facets, because rpa takes extremeness of scores into account, and Madeline G
has a very extreme profile. In such cases, rpa probably overestimates agreement; this is one of its
limitations. But empirical tests (McCrae, 1993) have shown that it is generally superior to
Cattell's rp as a measure of overall profile agreement.
The Interpretive Report also uses rpa statistics to pinpoint agreement or disagreement on
specific factors and facets. Madeline and her husband disagreed on twelve facets and on two
factors, Neuroticism and Conscientiousness. Madeline regarded herself as very low in
Neuroticism and high in Conscientiousness, whereas her husband saw her as high in Neuroticism
and low in Conscientiousness. Within the six Conscientiousness facets, there was both agreement
and disagreement: Both believed that she was high in C4: Achievement Striving and very low in
C6: Deliberation, but she saw herself as high in C3: Dutifulness whereas he saw her as very low.
Here is a woman with lofty goals who sets out to achieve them without much thought about the
ramifications of her actions. Perhaps she focused on the ends and viewed herself as highly
principled; perhaps he focused on the means, and saw her as unscrupulous.
How should observer rating data be integrated with self-report data in the interpretation
of individual cases? First, they can be used to evaluate the quality of the self-report. Many
validity scales have been devised to assess the trustworthiness of self-reports, but evidence
suggests that they are of limited value (Piedmont, McCrae, Riemann, & Angleitner, 2000). An
independent source of information is preferable. A comparison with her husband's ratings
suggests that overall, Madeline's self-report is valid, but that there are some particular trait
assessments (such as C6: Dutifulness) that are questionable.
Second, the two sources can be combined to provide an optimal estimate of personality
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trait levels. It is probable that Madeline is neither as dutiful as she says or as unethical as her
husband claims; averaging them should give a better estimate of the true level. (In fact, the
Interpretive Report provides an average with a slight adjustment to account for the fact that the
variance of means is reduced; see McCrae, Stone, Fagan, & Costa, 1998).
But there is a third possibility, of particular importance in clinical settings, where the
psychologist expects to interact with the client on repeated occasions. It is not necessary to stop
the assessment after the questionnaires have been scored. Instead, discrepancies between two
sources ought to be explored with the client, the observer, or both. On the one hand, that should
yield a better assessment of the disputed trait; on the other hand, it may offer insights into the
nature of their relationship. It does not bode well for a marriage when one partner thinks the
other is unethical, and in this case, Madeline G's relationship ended shortly after the assessments.
The Estimation of Latent Traits
Riemann, Angleitner, and Strelau (1997) provided an elegant example of the integrative
use of data from multiple observers and self-reports. They assessed personality using self-reports
and ratings from two informants on the NEO-FFI in a sample of mono- and dizygotic twins.
Typically, behavior genetic studies only use self-reports, and partition the variance into genetic,
shared environmental, and non-shared environmental effects. Most behavior genetic studies of
personality have shown that the shared environment (experiences shared by children living in the
same family) accounts for little or no variance; instead, personality is about equally determined
by genetic influences and the non-shared environment (Bouchard & Loehlin, 2001). When
Riemann et al. analyzed self-reports, they reported heritabilities, a measure of the proportion of
variance that arises from genetic differences, of .42 to .56.
In these analyses, however, the non-shared environment term is somewhat mysterious: It
includes real effects on personality that are due to unique experiences of different children in the
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same family (such as the fact that one took piano lessons whereas the other studied the flute), but
it also includes measurement error. It is possible to eliminate random measurement error by
correcting for test unreliability; this typically increases the estimate of genetic effects modestly.
But reliability estimates only deal with random error, not systematic bias. For example, a
rater may think that a target is more extraverted than the target actually is, but because the rater
maintains this view consistently, the misperception does not introduce unreliability. Riemann et
al. used data from two raters to estimate heritability using latent trait analyses, in which both
random error and systematic biases of the two raters were statistically controlled. In this design,
the heritabilities were higher (.57 to .81); and when the latent traits (the "true scores") were
estimated from a combination of self-reports and the two informant ratings, heritabilities were
even higher, .66 to 79. This study suggests that the heritability of personality traits has been
systematically and substantially underestimated by mono-method studies.
Mono-method studies may also have been misleading with respect to factor
intercorrelations. Digman (1997) proposed that the Big Five factors were themselves
intercorrelated yielding two factors he called α, Personal Growth, and β, Socialization. Markon,
Krueger, and Watson (2005) elaborated on this scheme, using data from a meta-analysis of selfreport studies. However, using multitrait, multimethod confirmatory factor analyses of selfreports and peer- and parent ratings, Biesanz and West (2004) found that "none of the Big Five
latent factors were significantly correlated" (p. 865), and suggested that within-method
evaluative biases were probably responsible for the apparent higher-order structure of FFM
factors.
Personality and its Changes in Alzheimer's Disease
Although geriatricians have often observed that there seem to be personality changes in
patients with Alzheimer's disease, there was very little research on the topic until the 1990s. One
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of the major reasons for that was, of course, that the self-report instruments typically used to
assess personality were of dubious applicability. Would dementing patients have insight into
their own personality, or indeed, would they be able to complete a questionnaire at all? Certainly
not in the later stages of the disease.
Siegler and her colleagues realized that observer ratings provided a feasible alternative
(Siegler et al., 1991). They asked caregivers to rate 35 patients with memory impairment on an
older version of the NEO-PI-R in two conditions: as they were now, and as they had been before
onset of the disease (the premorbid ratings). The premorbid profiles were generally in the normal
range, but there were dramatic differences for the current description: Patients were seen as high
in Neuroticism, low in Extraversion, and very low in Conscientiousness. The increase in
Neuroticism was not surprising, because Alzheimer's disease had often been linked to
depression. But no one had anticipated changes in Conscientiousness, although they seem
obvious in hindsight: People who have difficulty concentrating and remembering show behavior
that is poorly organized and not goal-directed.
That ground-breaking study, subsequently replicated by several teams of investigators,
was imperfect in a few respects. First, it was not clear if the premorbid ratings were accurate,
because they depended on the memory of the caregiver and might be distorted by contrast with
current traits. For example, premorbid Conscientiousness might have been overestimated
because it was so much higher than current levels. Strauss, Pasupathi, and Chatterjee (1993)
recruited two independent raters—the caregiver and another friend or relative—and asked for
premorbid and current ratings of the patient. The two raters generally agreed on both ratings,
suggesting that both were accurate reflections of the patient's personality at different times.
In a later study, Strauss and Pasupathi (1994) obtained observer ratings of Alzheimer's
patients on two occasions, one year apart. They showed continuing changes in the direction of
Observer Ratings 17
higher Neuroticism and lower Conscientiousness over the course of the year, suggesting that
observer ratings are sensitive to relatively small changes.
Observer ratings have also been used to study other psychiatric disorders in which selfreports from patients were suspect, including Parkinson's disease and traumatic brain injury. In
addition, Duberstein, Conwell, and Caine (1994) gathered informant reports about suicide
completers as part of a "psychological autopsy," which suggested that suicide completers are
more likely to be closed than open to experience.
Portraits of Historical Figures
Was Abe really honest? Was Washington cold? We cannot ask these men to complete
self-report questionnaires, and it is not clear how much we would learn from reading the many
biographies that have been written about each of them, because the data would not be
standardized in a way that made meaningful comparisons possible. Rubenzer, Faschingbauer,
and Ones (2000) solved this problem by inviting biographers of U.S. Presidents to describe their
subjects using observer rating forms of the NEO-PI-R, the California Adult Q-Set (Block, 1961),
and a set of adjective scales (Goldberg, 1990). (See Song and Simonton, this volume, for another
approach to the assessment of historical figures.)
It is one thing to ask caregivers to rate the personality of an Alzheimer's patient as he or
she was five years ago; it is another to ask historians to rate the personality of an individual who
has been dead for two centuries. How would they respond to items like "[George Washington]
really loves the excitement of roller coasters" or "[Abraham Lincoln] believes that the 'new
morality' of permissiveness is no morality at all," when these are clearly anachronistic?
Fortunately, Rubenzer et al. only identified three such items in the NEO-PI-R, and even those
could probably be meaningfully rated: Does anyone really think that Washington would have
loved roller coaster rides if he had been given the opportunity to try one?
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Rubenzer and colleagues argued that their assessments were valid because they were
internally consistent and showed cross-rater agreement (using the rpa measure) comparable to
that seen in contemporary peer rating studies. Based on descriptions by 10 experts, George
Washington was average in Neuroticism, low in Extraversion, Openness, and Agreeableness, and
very high in Conscientiousness—a portrait that seems to aptly characterize his steadfast but
formal personality. Lincoln was rather more interesting, scoring high on Neuroticism,
Extraversion, Agreeableness, and Conscientiousness, and very high on Openness. The high
Neuroticism scores are consistent with his well-known episodes of depression, and the high
Openness is seen in his legendary love of books. Curiously, although he was generally agreeable,
he was ranked very low in Straightforwardness, being a far shrewder politician than he pretended
to be.
McCrae (1996) reported a case study of the French-Swiss philosopher, composer, and
novelist, Jean-Jacques Rousseau. Figure 1 shows his profile, based on ratings by a political
scientist who had written a book on his political ideology. In this Figure, the five factor scores
are given on the left, and the 30 facet scales are grouped by factor toward the right. Because only
one rater was available, interrater agreement could not be assessed, but this profile is consistent
with the writings of Rousseau's contemporaries, who described both his paranoia and his genius.
Like Madeline G, Rousseau shows an extreme profile, with scores literally off the chart for
several facets (e.g., N4: Self-Consciousness, O1: Fantasy). Perhaps this reflects the rater's use of
extreme response options, but it must be recalled that Rousseau was one of the most
extraordinary figures in history, and these ratings may be completely accurate. If the reader still
feels the need for a second opinion on Rousseau—good. Personality psychologists, clinicians,
and historians should all cultivate a taste for multiple assessments of personality (McCrae, 1994).
Observer Ratings 19
____________________
Figure 1 about here
____________________
Personality Assessment in Chimpanzees
Another chapter (Vazire, Gosling, Dickey, & Shapiro, this volume) has discussed the use
of observer ratings to assess personality in other species, but we feel it is worth focusing on some
issues in observer ratings of the personality of our closest nonhuman relatives, chimpanzees (Pan
troglodytes). King and Figueredo (1997) asked zoo workers to rate individual chimpanzees on a
43-item questionnaire that was based on adjective measures of the FFM. Each adjective was
accompanied by a short description to clarify the intended construct. Factor analysis of the 43
items suggested six factors. The first factor, Dominance, was a large chimpanzee-specific factor
that was indicative of competitive prowess. The remaining five factors were analogous to the
domains of the FFM.
Because the validity of observer ratings of chimpanzee personality cannot be assessed by
comparing them to self-reports, King and Figueredo (1997) had multiple raters assess each target
and used intraclass correlations to show that individual [ICC(3, 1)] and mean [ICC(3, k)] ratings
were consistent across raters (Shrout & Fleiss, 1979). The interrater reliability of individual
ratings can be used to compare reliabilities of similar factors across different species even if the
number of raters differs. The interrater reliability of mean ratings are typically used to describe
the reliability of scores based on multiple raters. Because using a mean of several ratings will
reduce measurement error, it should be no surprise that the reliability of mean ratings will be
higher.
A recent study (King, Weiss, & Farmer, 2005) on the personality of chimpanzees in zoos
and a sanctuary in the Republic of Congo (Brazzaville) challenged Kenny’s (2004) conclusion
Observer Ratings 20
that length of acquaintance has little effect on the reliability of ratings. Raters at zoos knew their
charges for an average of 6.5 years, and there were a mean of 3.7 raters per zoo chimpanzee.
Raters at the sanctuary knew their charges for a mean of only 6.9 months, but each chimpanzee
in this habitat was rated by an average of 16.2 raters (King, Weiss, & Farmer, 2005). Interrater
reliabilities of individual ratings were considerably higher (Mdn = .46) for ratings of
chimpanzees in zoos than for ratings at the sanctuary (Mdn = .26), suggesting that length of
acquaintance does affect accuracy, and that one should be skeptical of any conclusions drawn
from single ratings of chimpanzees based on limited acquaintance. However, the same study
showed that the reliabilities of the mean ratings of the chimpanzees in the African sanctuary
(Mdn = .87) were comparable to or greater than those of chimpanzees living in zoos (Mdn = .77).
In short, the use of more raters per chimpanzee all but eliminated any disparity between the
reliabilities of ratings that arose due to differences in the length of acquaintance.
Observer ratings of chimpanzee personality traits can also be validated by a pattern of
correlations with external criteria. Supporting evidence has been found in two studies that have
related each of the chimpanzee factors to frequencies of relevant behaviors (Pederson, King, &
Landau, 2005), and Dominance, Extraversion, and Dependability (analogous to
Conscientiousness) to ratings of subjective well-being (King & Landau, 2003).
Cautions in the Use of Observer Ratings
We advocate multimethod approaches to personality assessment because no method,
including observer ratings, is perfect. Some of the potential problems with observer ratings are
familiar from the self-report literature. Acquiescence, extreme responding, and random
responding are threats to the validity of observer ratings much as they are to self-reports. Efforts
to identify or correct invalid protocols have so far met with limited success (Piedmont et al.,
Observer Ratings 21
2000), in part because even carelessly completed inventories typically have some useful
information: The validity of most assessments is a matter of degree (Carter et al., 2001). Users of
both Form S and Form R of the NEO-PI-R are thus given four rather conservative rules for
discarding protocols as invalid: (1) more than 40 missing items; (2) a response of disagree or
strongly disagree to the validity check item, "I have tried to answer all these questions honestly
and accurately;" (3) a no response to the validity check item "Have you entered your responses in
the correct areas?;" or (4) random responding, as evidenced by strings of repetitive responses
(e.g., more than six consecutive strongly disagrees). Even in these instances, however, clinicians
are advised to retain the responses, discuss the potential problems with the respondent, and
interpret the profile cautiously. For research purposes, the optimal solution is to score all
protocols (replacing missing items with neutral or the group mean) and report analyses with and
without the exclusion of nominally invalid protocols.
McCrae et al. (2005) extended the assessment of protocol validity to entire samples in
their cross-cultural study of observer-rated personality. Personality questionnaires are familiar to
American and European college students, but they are less widely used in Asia and Africa, so
there is reason to believe that the quality of personality data might be better in some cultures than
in others. McCrae et al. created a Quality Index that took into account random responding,
acquiescence, missing data, the fluency of the sample in the language of the questionnaire, the
quality of the translation, and miscellaneous problems reported by the test administrator. This
index was not used to exclude samples, but to help interpret the data. For example, the factor
structure of NEO-PI-R Form R was less well replicated in African cultures. Was that because
African cultures have a personality structure that is different from that of Americans, or was it
simply due to error of measurement? The fact that the Quality Index was low in most of the
African cultures suggested the latter interpretation, and when noise was reduced by pooling
Observer Ratings 22
responses from the five African cultures, the FFM structure was clearly replicated.
Judging by the attention it has been given by psychometricians, the major concern with
self-reports is social desirability, individual differences in the tendency to exaggerate one's
strengths and minimize one's failings. One of the chief merits of observer ratings is that they do
not share this bias: Mary Jones may be particularly prone to socially desirable responding, but
there is usually no reason to think that her raters will also feel a need to paint a rosy picture of
her.
Although the assessment and control of individual differences in socially desirable
responding is problematic (Piedmont et al., 2000), this does not mean that there are no evaluative
biases in self-reports and observer ratings. Individuals who are applying for a job typically score
higher on self-reports of all desirable traits than disinterested volunteers, and their scores must be
interpreted in terms of job applicant norms, not volunteer norms. Similar biases might well be
found in observer ratings if the observer has an interest in the outcome. For example, spouse
ratings of job applicants might also be unrealistically favorable, because the whole family would
benefit from the job offer.
A striking instance of negative bias in observer ratings was reported by Langer (2004),
who administered Form S and Form F of the NEO-PI-R to 20 couples being evaluated for child
custody litigation. Their mean self-reports for the five factors all fell within the normal range,
although they tended toward higher-than-average Extraversion, Agreeableness, and
Conscientiousness, and lower-than-average Neuroticism scores. Their mean ratings of their
spouses, however, were dramatically different: They described their spouses as high in
Neuroticism, low in Openness, and very low (mean T-scores = 26.3 and 25.2) in Agreeableness
and Conscientiousness. The moral is that in interpreting observer rating data in groups or
individuals, one must take into account normative biases attributable to the situation. (Among
Observer Ratings 23
chimpanzees, situational biases to consider in rater reports may include whether the individuals
live in the wild, sanctuaries, or research labs.) Ideally, this would mean the use of relevant norms
(e.g., from a large sample of spouse ratings of custody litigants); otherwise, clinical judgment
must be used to discount suspicious data. It is of considerable interest that Langer reported Form
S/Form R correlations ranging from .18 to .46 for the five factors, with significant agreement for
Extraversion and Openness. This suggests that some validity in individual differences is retained
even when the mean levels are dramatically distorted.
Future Directions
Research on Ratings
A number of researchers have been interested in the factors that affect agreement
between judges (Funder et al., 1995; John & Robins, 1993). Differences in observability and
evaluation appear to influence cross-observer agreement, and Extraversion is usually found to be
the most consensually rated factor (Borkenau & Liebler, 1995). In a cross-cultural extension of
that work, McCrae et al. (2004) reported similar findings for American and European samples,
but not for Chinese data. Perhaps agreement across raters depends on the salience of the trait in
the raters' culture.
There is ample evidence that ratings from observers who are well-acquainted with the
target provide reliable and valid assessments of the full range of personality traits, but many
questions remain about how to optimize observer rating assessments. Is some particular
combination of raters (e.g., a spouse and a friend) preferable, and should these sources be
differentially weighted? Should special instructions be given, perhaps asking raters to focus on
the person in a particular context (at work, at home), or emphasizing that they should report both
strengths and weaknesses? We know already that observer rating methods and instruments work
Observer Ratings 24
well in translation and across a variety of cultures (McCrae et al., 2005); are any special
problems posed by the use of informant ratings of personality gathered via the Internet (e.g.,
"flaming")?
In most cases, research using observer ratings replicates findings based on self-reports,
but in a few instances, substantive findings differ across these methods. For example, crosssectional ratings of Agreeableness consistently increase across the adult lifespan when selfreports are examined, but not when observer ratings are analyzed (McCrae et al., 2005). How do
we account for such discrepancies, and which set of findings should we believe?
In the assessment of chimpanzee personality, continued work is needed on assessment
instruments. One important question about chimpanzee personality is whether deviations from
the FFM structure previously reported are an artifact of the specific measure. The questionnaire
King and Figueredo (1997) used was based on the human FFM, but it was not a standard
measure, and it was modified for use with chimpanzees. Thus, we do not know whether the
Dominance factor and a unipolar Agreeableness factor found in chimpanzees reflect unique
characteristics of chimpanzees' personality trait structure, or whether these are attributable to the
particular set of adjectives chosen. Observer rating studies need to be conducted in which human
targets are rated on the chimpanzee personality questionnaire and a well-validated measure of the
FFM. Factor analysis of the chimpanzee items in this human sample would indicate whether the
human or chimpanzee structure would be found using this instrument (cf. Gosling, Kwan, &
John, 2003). Correlations with the FFM measure would aid in the interpretation of the
chimpanzee items and factors.
Wider Applications
Observer ratings provide a simple, valid, and still-underutilized source of personality
data. If researchers want to evaluate the correlation of Scale A with Scale B, they typically
Observer Ratings 25
administer them to college students. There is no reason why the students should not be asked to
provide observer ratings rather than (or in addition to) self-reports. With some thought,
researchers may be able to obtain more generalizable findings in this way, by requiring that
raters select targets of specified age, gender, or SES.
Informant ratings can also be used effectively on hypothetical targets. The Personality
Profiles of Cultures Project (Terracciano et al., 2005) included informant reports on the traits of
the "typical" member of each culture, allowing a comparison of national stereotypes (e.g., the
typical Canadian is thought to be more compliant than the typical American). Informants can rate
ideal romantic partners (Figueredo et al., 2005) or preferred roommates. Strictly speaking, these
are not observer ratings, because the hypothetical targets have not been observed. They do,
however, provide useful psychological information using the observer rating methodology.
Observer ratings have one more important feature that makes them especially valuable
for survey research: They require minimal involvement of the target. Survey researchers often
complain that their interviews do not leave enough time to administer a full personality
inventory, and if they assess personality at all, it is likely to be with a handful of questions of
limited reliability. But most survey respondents can easily identify a significant other or friend
who could be asked to make ratings of the respondent's personality and return them to the
interviewer, either in person or by mail (cf. Achenbach, Krukowski, Dumenci, & Ivanova, 2005).
Although those data might not meet the stringent sampling requirements of the study, they would
provide important auxiliary information that could confirm or extend results of the interview
assessment and validate the abbreviated self-report personality assessments. Obviously, the same
advantage should make observer ratings attractive to clinicians or researchers whose current test
batteries already tax the patience of their clients or research participants.
Observer Ratings 26
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Observer Ratings 33
Jean-Jacques Rousseau
Figure 1. Revised NEO Personality Inventory profile for J.-J. Rousseau, as rated by A.
M. Melzer, adapted from McCrae, 1996. Profile form reproduced by special permission of the
publisher, Psychological Assessment Resources, Inc., 16204 North Florida Avenue, Lutz, Florida
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McCrae. Copyright 1978, 1985, 1989, 1992 by PAR, Inc. Further reproduction is prohibited
without permission of PAR, Inc.
Observer Ratings 34
Recommended Readings
Benet-Martínez, V., & John, O. P. (1998). Los Cinco Grandes across cultures and ethnic groups:
Multitrait multimethod analyses of the Big Five in Spanish and English. Journal of
Personality and Social Psychology, 75, 729-750.
Costa, P. T., Jr., & Piedmont, R. L. (2003). Multivariate assessment: NEO-PI-R profiles of
Madeline G. In J. S. Wiggins (Ed.), Paradigms of personality assessment (pp. 262-280).
New York: Guilford.
Funder, D. C., Kolar, D. C., & Blackman, M. C. (1995). Agreement among judges of
personality: Interpersonal relations, similarity, and acquaintanceship. Journal of
Personality and Social Psychology, 69, 656-672.
Kenny, D. A. (2004). PERSON: A general model of interpersonal perception. Personality and
Social Psychology Review, 8, 265-280.
McCrae, R. R. (1994). The counterpoint of personality assessment: Self-reports and observer
ratings. Assessment, 1, 159-172.
McCrae, R. R., Stone, S. V., Fagan, P. J., & Costa, P. T., Jr. (1998). Identifying causes of
disagreement between self-reports and spouse ratings of personality. Journal of
Personality, 66, 285-313.