The Neurology of Proverbs · language (e.g. proverbs, idioms, speech formulas, and indirect requests) point to an important role of the right hemisphere (RH). Research describing

Behavioural Neurology, 1990,3, 169-187

The Neurology of Proverbs

DIANA VAN LANCKER

Neuropsychiatric Research Institute and Department oj Neuroscience, University of North Dakota Medical School, and Neurology Service, Fargo V AM ROC, Fargo, North Dakota, USA

Correspondence: Dr. Diana Van Lancker, Department of Neuroscience, University of North Dakota School of Medicine, 1919 Elm Street North, Fargo, ND 58102

Although proverb tests are commonly used in the mental status examination surprisingly little is known about either normal comprehension or the interpre-tation of proverbial expressions. Current proverbs tests have conceptual and linguistic shortcomings, and few studies have been done to investigate the specific effects of neurological and psychiatric disorders on the interpretation of proverbs. Although frontal lobes have traditionally been impugned in patients who are "concrete," recent studies targeting deficient comprehension of non literal language (e.g. proverbs, idioms, speech formulas, and indirect requests) point to an important role of the right hemisphere (RH). Research describing responses of psychiatrically and neurologically classified groups to tests of proverb and idiom usage is needed to clarify details of aberrant processing of nonliteral meanings. Meanwhile, the proverb test, drawing on diverse cognitive skills, is a nonspecific but sensitive probe of mental status.

Introduction

Abilities to recognize and interpret certain kinds of nonliteral language, especially proverbs and idioms, have long been believed to reflect special aspects of cognitive function (Buhler, 1907; Bronner et at., 1927; Piaget, 1923; Benjamin, 1944), and have been used as a tool in evaluation of cognitive and mental status (Lezak, 1983; Fogel, 1965, Cummings and Benson, 1983). Proverbs and idioms are included in intelligence testing (Wechsler Adult Intelligence Scale, 1955; Stanford-Binet Test of Intelli-gence), in formal psychiatric and neurological evaluation of mental status, (Cummings, 1985; Strub and Black, 1985) and in clinical bedside testing. Interpretation of proverbs and idioms is still routinely used in the diagnosis of inter alia, dementia, psychiatric disorders and confusional states.

Viewed as a problem with "abstract thinking" (Goldstein, 1936; Gold-stein and Scherer, 1941), or "verbal abstraction" (Gorham, 1961), a "concrete" interpretation of "People who live in glass houses shouldn't throw stones" (proverb) or "a loud tie" (idiom) is taken as an indication of deficient cognition and/or neurological disease, while a bizzare interpre-tation may be said to reflect thought disorder (Cummings, 1985). Aging has been associated with an increase in "concrete" interpretations of proverbs (Bromley, 1957). However, the conceptual problems inherent in the abstract/concrete dichotomy are reflected in Lezak's (1983) comment that a

0953-4180/90/030169+ 19 $3.50/0 -© 1990 CNS (Clinical Neuroscience) Publishers

170 DIANA VAN LANCKER

mentally dilapidated elderly patient can "express suitable meanings for familiar (proverbs) while being unable to think abstractly" (p. 261) (emphasis mine; see discussion of familiar versus unfamiliar nonliteral expressions below). In their influential book on behavioural-neurological evaluation, Strub and Black (1985) state that "abstract thinking, which is perhaps the highest level of cognition, may be readily assessed by the use of proverbs ... " Indeed, a heady excitement about the "utilization of proverbs as a tool in evaluating mental processes" is reflected in Gorham's (1961) survey of applications of the technique in the 1950s to "psychiatric conditions, LSD, lobotomy, organic damage ... simulated high altitude ... (and) personnel selection" (pp. 57-58).

Despite the ubiquity and robustness of proverbs and idioms as probes of mental function, there is considerable uncertainty among clinicians about how to evaluate patients' performance and what a response means for the differential diagnosis. Little is known about the qualitative details of patient performance, such as the types of interpretative errors that would serve as a signature of certain focal brain lesions or specific psychiatric conditions; nor is the inverse well understood: a predictable effect of brain damage on proverb performance.

The common practice of using proverbs to evaluate mental status highlights our need to know more about how and where nonliteral hnguage is processed in the brain, and what kinds of brain dysfunction interfere with idiom and proverb interpretation. Better knowledge of normal nonliteral language use and the neuropathology of nonliterallanguage deficits would make the proverbs test more useful in clinical assessment, and would further our understanding of brain function underlying communicative and cogni-tive ability. The purpose of this review is to reevaluate issues underlying use of non Ii teral language as a clinical tool.

Previous Work

The most well known previous work on proverb interpretation as a psychological tool is by Gorham (1956 a, b), who published results on his test of proverb interpretation, with performance scores averaged from over a thousand subjects, including adults, servicemen, children, and students. Correlations between the Gorham Proverbs Test and 16 other neuropsychologi-cal batteries were also provided. This test has been used as a model for screening tests in neurology and psychiatry (Strub and Black, 1985; Cum-mings, 1985). It is the one most used in clinical research (Brinton et al., 1985; Carpenter and Chapman, 1982; Elmore and Gorham, 1957) and, recently, for further testing in normal subjects (Nippold et at., 1988; Nippold and Fey, 1983; Penn et al., 1988a, b).

The Gorham Proverbs Test consists of two parts. In the first part, free verbal interpretations are elicited and later scored on a 3-point scale corresponding to degree of "concreteness," as subjectively determined by the examiner. In the second part, subjects select one offour multiple choice answers provided for each proverb. Foils (wrong answers) are designed to provide wrong, partial and concrete responses.

THE NEUROLOGY OF PROVERBS 171

The California Proverb Test, developed by Delis et al. (1984), also using free verbal responses and multiple choice, has also been widely assessed in clinical screening, but normative data have not yet been published. * Expanding the scoring categories from the three levels in Gorham's test, this test provides a set of ten cognitive-linguistic categories for classifying responses.

Strub and Black (1985), following Gorham's format, list five proverbs "in ascending order of difficulty," scoring the "degree of abstraction demonstrated by the patient in explaining the proverb," again as subjecti-vely determined by the examiner.

In clinical practice, for interpretation of idioms, a few standard idioms are given (Cummings, 1985), and clinicians evaluate responses without recourse to published exemplars or standardized scoring criteria.

Two main shortcomings of these tests, touching upon familiarity and evaluation, are reviewed below.

F atniliari ty

The first issue to be addressed is proverb or idiom diificulty, which is related to familiarity. These tests of proverb interpretation are usually meant to include both "easy" and "difficult" (or "simple" and "complex") exemplars (Cummings, 1985), a scale believed to correlate with degree of "abstract-ness." According to Strub and Black (1985), "Don't cry over spilt milk" is simpler than "Rome wasn't built in a day," which, in turn, is less difficult than "A drowning man will clutch at a straw" (p. 131). But the criteria for these "difficulty" levels are not obvious. The most difficult, and therefore allegedly also the most abstract, is said to be "The hot coal burns; the cold one blackens." Reflection on these examples suggests that the operational feature is familiarity.

What makes a proverb difficult is that it is unfamiliar, not that it is more abstract. Indeed, studies investigating this problem have shown that fami-liar and unfamiliar proverbs elicit different kinds of results (Penn et al., 1988; Cunningham et al., 1987; Popiel and McRae, 1988; Kempler and Van Lancker, 1989). As might be expected, unfamiliar proverbs elicit variable responses or no responses from normal subjects. Similarly, people select figurative interpretations only for idioms they are familiar with, and their preference for idiomatic meanings is correlated with degree of familiarity of the test items (Schraw et al., 1988). Normal subjects do not agree in their interpretations of unfamiliar proverbs; instead, subject agreement for nonliteral meanings is found only for familiar items, and only for those in the respondent's native language (Kempler and Van Lancker, 1989).

Surprisingly, the question offamiliarity has not been taken into account in traditional proverb testing. Yet, by definition, proverbs and idioms are made up of afixedform associated to a conventional meaning. It would not seem useful or reasonable to ask a subject to interpret a conventional meaning ofa fixed form that he or she has never heard of before. Taking an example from Strub and Black (1985), it is challenging even for the normal intellect to

* Unpublished data from 86 normal control subjects were analyzed according to age, education, and age-adjusted vocabulary by Mandala (Delis, 1989)


imagine the "right" response for "The hot coal burns; the cold one blackens." Because of a given proverb's unfamiliarity to normal subjects, no consensual agreement emerges, and without such consensual agreement from a sampled population, the patient's response cannot be validly assessed as right or wrong, normal or abnormal, much less, given the intrinsic vagueness of the most pertinent categories, abstract or concrete.

It might be argued that only unfamiliar proverbs should be used in proverb testing since they are not subject to a "learned response," but require a newly created, metaphoric, cognitive invention, thereby more directly probing the "abstract attitude." (Carrying this view somewhat further, one might present the target stimulus in Latin.) This notion, however, misses the point that proverbs and idioms, by definition, mean something other than the standard lexical meanings of their constituent words, and that both the form and meaning must be acquired, or learned. The proverb "While the cat's away, the mice will play" has nothing to say about cats or mice; the idiom "She has him eating out of her hand" is not referring to a meal or a distal body part, if their conventional meanings are appropriately associated to their fixed forms. Attempts to interpret mean-ings of unfamiliar proverbs and idioms, such as those translated out of other languages, result in an array of guesses which usually have little in common with the actual conventional meaning (Van Lancker, unpublished data). The degree of "abstractness" is impossible to discern from these varying responses.

The ability to produce the fixed forms and to recognize the conventional meanings is internalized, but directly interpreting the meanings is not. Such interpretation requires both inference and verbal processing, in order to depict, or to "abstract," the meaning which is not denoted by the constituent words of the expression. (These cognitive skills are discussed below.) Using an unfamiliar proverb or idiom does not make the proverb test more abstract; it makes the task unclear. Requesting or expecting a nonliteral interpretation an unfamiliar expression evokes uncertainty in the su~ject about the task and uncertainty for the examiner about evaluating the response.

Evaluation

Tests of proverb interpretation usually rely upon elicited verbal responses, involving an explanation by the subject of the meaning of the i~em. The examiner says, "Do you know the proverb, 'People who live in glass houses shouldn't throw stones'? What does that proverb mean?" Two problems arise from attempts to analyze these verbal responses, one involving general task demands, and the other involving evaluation. The two problems are interrelated.

First, the task is demanding. As alluded to above, producing an accurate interpretation requires, in addition to knowledge of the nonliteral item, grammatical skills, adequate verbal expression, the metalinguistic ability to provide a definition, and the cognitive process of making an inference. Patients deficient in these skills are at a disadvantage, and a propositional-or literal----Ianguage disorder will surely confound assessment of nonliteral


language, leading to an error in judging cognitive performance. Even more problematical is the challenge faced by the examiner in the evaluation of the response.

Scoring of verbal responses is difficult because they are open-ended, and is compounded by the vagueness of the notions "abstract" and "concrete," as Gorham acknowledged:

The greatest difficulty was presented by the responses which were not clearly good abstractions nor complete failures. In these cases, a value was assigned arbitrarily and sometimes changed during the process of scoring the original population (Gorham, 1956, a, p. 3).

Andreasen (1977) found interrater reliability for the Gorham Proverbs test to be poor, and the validity of the test in a clinical setting to be questionable (p. 471). Examples from the revised Strub and Black version will further illustrate the problem (1985). In the Strub and Black test, for the proverb "Rome wasn't built in a day," the answer "Don't do things too fast" is given as a score of 1 (semi-abstract), while the answer "It takes time to do things well" is given a score of 2 (abstract). It is difficult to see why "Don't do things too fast" is deemed less abstract than "It takes time to do things well."

Efforts at revision in the California Proverb Test have not significantly eliminated the evaluation stumbling block. Instead, the cognitive-linguistic categories for classifying responses have reportedly proven difficult to use reliably in rating actual responses (Delis, 1989).

Norlllative Data

Presumably drawing on Gorham's work, Cummings (1985) states that "Proverbs can be understood by most individuals with a high school education". But there is surprisingly little other, more recent normative information on proverb and idiom interpretation, considering the popular-ity of the tests. Gorham's (1956c) study provides only group means, along with correlations with other psychological tests. From these data, we know only mean performance values for large groups-nothing about types of errors. As mentioned previously, the California Proverbs Test also has provided no published normative information. Thus, qualitative descriptions of typical responses from normal subjects, in comparison with clinical subjects, are absent, and reliable criteria for evaluating responses are not available. Without such criteria, the clinician cannot be confident about how to classify patients' responses, nor can the effects on performance of education, cultural differences, occupational history, or intelligence be taken into account. Much work with normal subjects is needed to establish normative performance on tests of proverb and idiom interpretation.

The Neurology of Proverbs and Idiollls

Given the limited data on normal proverb and idiom interpretation, it is not surprising that little is known about neuro-anatomical substrates or non-literal language function. Deficient processing of proverbs and related


nonliteral expressions has been associated with frontal lobe dysfunction (Benton, 1968, see below p. 179; Stuss and Benson, 1986; Cummings, 1985), right hemisphere (RH) damage (Benton, 1968, see below p. 179; Van Lancker and Kempler, 1987; Winner and Gardner, 1977; Brownell et al., 1986; Weylman et al., 1989) and left hemisphere (LH) damage (based on propositional language deficits).

How to differentiate psychiatric groups using nonliteral language re-sponses has been only sparsely investigated. Gorham (1956a) reported that a large group of chronic schizophrenic patients differed significantly from normal-control subjects in performance on his Proverbs Test, but how the groups differ was not presented. Elmore and Gorham (1957) reported that subjects with "chronic schizophrenic and organic (without functional psychosis) diagnoses" differed from matched normal-controls in the multi-ple choice form of the Gorham Proverbs Test; but, again, the distinguishing features are not described. (See Gorham's 1961 review of the use of proverb interpretation in psychiatric clinics.) Cummings (1985, p. 13) mentions that "bizarre, paranoid, or idiosyncratic responses" are often elicited from psychotic patients, while "macabre, pessimistic, or hopeless interpretations" often come from depressed patients. Cummings' valuable clinical observa-tions have not yet been supported by controlled research studies.

Overall there is a lack of systematic information on the effect of different kinds of brain damage and dysfunction on understanding and interpre-tation of proverbs and idioms. Performance differences in neurological and psychiatric groups on comprehension and interpretation of proverbs and idioms remain to be established. Despite their prominence in the clinic, there is as yet no neurology of proverbs.

Current Status

The foregoing can be summarized as follows: proverb and idiom screening is potentially useful as a clinical tool, and accurate characterization of these verbal and cognitive deficits could aid in neurobehavioral diagnosis and cognitive rehabilitation; however, available tests are flawed, distinguishing features of normal and aberrant responses have not been codified, and the neuroanatomical substrates of nonliteral language function are not well understood.

What is known from psycholinguistic and neurolinguistic studies is that nonliteral and literal language are organized according to different prin-ciples in the mind and represented in different places in the brain. Several sources of information reveal these differences.

In psycholinguistic research, when asked to make judgments, recognize or recall items, people process familiar nonliterallanguage differently from literal language. Swinney and Cutler (1979) showed that subjects were significantly faster at judging a "natural English phrase" when shown idioms than when shown balanced literal phrases; Osgood and Hoosain (1974), Horowitz and Manelis (1973) and Simon (1974) have shown significant differences in recognition and recall of idioms, compared to novel phrases and sentences. Lieberman (1963) and Van Lancker et al. (1981)


reported that subjects could distinguish idiomatic from novel phrases from the acoustic signal alone. Other studies indicate that people process a figurative meaning first, when listening to a familiar idiom or proverb (Ortony et al., 1978; Gibbs, 1980). That is, normal listeners do not first "try" a literal interpretation, and then turn to a figurative meaning when the literal reading fails (Schweigert, 1986; Schweigert and Moates, 1988). For sarcastic and ironic statements, similarly, normal listeners comprehend the nonliteral (ironic) meaning first, and remember it better, than literal uses of the same expression (Gibbs, 1986). These studies support the notion that literal and figurative language are processed by different mental mechan-isms. Therefore, it follows that brain damage, or brain dysfunction, might affect literal and nonliterallanguage abilities differently.

Neurological Dissociation between Nonliteral and Propositional Language

Nonliteral language can be conceptualized as occurring on a continuum from reflexive or overlearned at one extreme and to novel, newly created, or "propositional," at the other (Fig. 1) (see Characterization of Nonliteral Language below, p. 19) (and see Van Lancker, 1975, 1988). Using this schema, whereby nonliterallanguage is made up of "subsets" differing from each other somewhat in specific properties oftheirJixedforms and conventional meanings, the notion that propositional and nonliterallanguage are mediated by disparate brain regions is supported by neurolinguistic data. Clinical studies have shown that various types of language along the propositional-nonliteral language continuum are differentially affected by focal brain lesions. In aphasic patients with propositional language impairments, recur-rent utterances appear (Code, 1982a), which often include nonliteral speech-expletives, social formulas, stereotyped phrases and cliches, serial and memorized speech-Oackson, 1915, 1958; Critchley, 1962, 1970; Benson, 1979; Eisenson, 1962; Espir and Rose, 1970; Van Lancker, 1973, 1975, 1988; Code, 1987). Aphasic patients fluent not infrequently produce nonliteral utterances, but are unable to produce parts of those same utterances in a propositional context; e.g. the patient who says "son of a bitch" cannot volitionally say the word "son" to refer to his male offspring. As the nonfluent patient recovers speech fluency, the repertory of fixed expressions often increases. The progression from a few stereotypies, through a larger number of fixed expressions, to grammatically produced (propositional) speech has been described by Alajouanine (1956). The

Indirect Requests Expletives

Idioms

FIG. I.


repertory of residual utterances varies across patients (Van Lancker, 1975; Code, 1987).

In a few patients, specific abilities to perform better on nonliteral speech than on propositional speech tasks have been observed: completion of idioms was reported by Geschwind et at. (1968) and by Whitaker et at. (1976) in patients with severe propositional language deficits. Using the notion that idioms were completed because they are "overlearned" does not fully account for these observations,. because many idioms are heard and used only occasionally compared to common propositional expressions. A case of nonpropositional inner speech, consisting of fragments of prayers and hymns, activated by brain injury, was recently described (Ellis et at. 1989).

The question about whether the intact left hemisphere mediates residual aphasic speech or whether the right hemisphere might be involved has been addressed by various investigators (Van Lancker 1975, 1988; Code, 1987). Furthermore, the association of an anterior/posterior axis with production versus comprehension of nonliteral language has been suggested by clinical observations of patients with Alzheimer's disease. Alzheimer patients, even in middle and late stages of the disease, produce social formulas with ease and fluency. In most Alzheimer cases studied, posterior cortical areas of the brain have become involved before anterior areas, and, as seen on neurologi-cal examination, frontal cortex and basal ganglia are relatively functional (Cummings, 1982; Cummings and Benson, 1983). This observation suggests that producing at least some kinds of non literal expressions is associated with intact frontal (or frontosubcortical) systems (see discussion of brain model for nonli teral language below).

The Possible Role of the Right Hemisphere (RH) in Nonliteral Aphasic Speech

The level of emotionality, prosodic intactness, and holistic structure of recurrent utterances leads one to implicate the RH in the production of these instances of residual speech, (Van Lancker, 1975, 1987), especially production of real word recurrent utterances (Code, 1982b, 1987), (although probably not production of recurrent consonant-vowel "non-sense" utterances (de Bleser and Poeck, 1985; Code, 1987)). Neurophysiolo-gical observations support Jackson's view that propositional speech can be represented in the LH and nonpropositional (or "automatic") speech is produced also by the RH. In their study of mouth asymmetry during aphasic speech, Graves and Landis (1985) reported greater openings on the right side of the mouth for spontaneous speech, repetition, and word list generation (propositional tasks), in contrast to greater openings on the left for serial speech and singing ("automatic" speech).

Various neurological observations suggest that residual aphasic speech is most likely represented in the RH (Kreindler and Fradis, 1968). Several clinical cases have been reported in which the nondominant RH appeared to be the site of aphasic speech (Landis et at., 1980; Cummings et at., 1979). Studies using the Wada procedure reported continued aphasic output


during anesthetization of the left (dominant) hemisphere (Kinsbourne, 1971; Czopf, 1981), implying that the residual aphasic speech was produced by the right (unanesthetized) hemisphere. Further, there have been reports of callosal-sectioned patients with linguistic expression via RH mechanisms (Levy et ai., 1971; Gazzaniga et ai., 1982; Sid tis et ai., 1981; Butler and Norsell, 1968). More dramatically, severa11eft (dominant) hemispherecto-mized adults with little or no propositional speech have been observed to produce exemplars of fluent, normally intoned nonpropositiona1 speech (Crockett and Estridge, 1951; Hillier, 1954; Smith, 1966, 1974; Bogen, 1973). Although alterations in spontaneous speech patterns following RH damage have not been systematically investigated, there are numerous clinical observations about deficient production of social interaction for-mulas and other instances of nonliterallanguage in such patients (Foldi et ai., 1983; Jaffe, 1978; Myers, 1979). The intrusive prayers and hymns described by Ellis et ai. (1989) followed bilateral, but primarily RH, injury. However, many globally aphasic patients, who have intact right hemi-spheres, do not ever produce significant nonliteral speech (or any other speech beyond nonsense syllables). This fact, in the light of the above evidence for involvement in residual speech, also requires explanation. How active the RH is in spontaneous production of non1itera11anguage remains to be studied.

That the RH does participate in normal speech production has also been suggested by recent advanced radiographic methods of observing brain function during behavior. Using measures of blood flow in the brain during performance of a task, it has been found that the RH is active in normal speech production (Ingvar and Schwartz, 1974; Larson et ai., 1978; Lassen et ai., 1978), and Ryding et ai. (1987) reported that during automatic speech (pronouncing the days of the week), the RH was more active than the left.

The role of the RH in comprehension of idioms and proverbs is more definite than is the picture for production. First, it is well established that the RH recognizes linguistic stimuli, so long as phonological or grammatical analysis is not involved (Zaidel, 1978, 1981, 1982). As idioms and proverbs do not require such analysis, but are recognized holistically, it is possible that the RI-I understands considerably more nonliteral than literal language. Indeed, it is often observed by clinicians and family members that aphasic patients with severe language comprehension deficits seem to understand a great deal more in conversational interaction than can be demonstrated in formal testing of propositional language (Holland, 1980). While some of this comprehension may be attributable to affective and gestural cues (Ross, 1981), it is likely that social formulas, idioms, and conventional expressions used in daily interaction are more available to these severely aphasic persons.

Winner and Gardner (1977) were the first to report that comprehension and interpretation of nonliteral expressions such as "heavy heart" are impaired by RH damage. Since then, other clinical studies have shown that comprehension of idioms and proverbs is significantly impaired by RH damage compared to normal-control subjects (Hier and Kaplan, 1980) or to


patients with LH damage (Myers and Linebaugh, 1981; Dronkers, 1984; Van Lancker and Kempler, 1987; Kempler and Van Lancker, 1989). To study comprehension of nonliteral language (idioms, proverbs and social formulas) without requiring verbal output from subjects, the Familiar and

1. I'd like to give you a piece of my mind (familiar phrase).

-

-

1. The dog's trying to give her a ride on the wagon (novel phrase).

FIG. 2.


Novel Language Comprehension (F ANL-C) test was developed (Kempler and Van Lancker, 1985). Nonliteral expressions were matched with literal sentences in word length, frequency oflexical items, and surface grammati-cal structure, and four line drawings were provided for each test item for a picture-matching response (see Fig. 2). In studies using the FANL-C, LH patients were significantly more impaired on the literal than the nonliteral sub test, while the opposite pattern was seen in patients with RH damage (Van Lancker and Kempler, 1987; Kempler and Van Lancker, 1989).

Another type of nonliterallanguage recently associated with RH func-tion is the indirect request. Indirect requests are conventional expressions which are normally interpreted nonliterally. For example, "Do you know what time it is?" and "Can you open the door?", given the appropriate context, are ordinarily not taken as questions, despite their grammatical form, but instead are interpreted as requests (to say the time or open the door). Deficient use of verbal context in appropriately (i.e. figuratively) interpreting indirect requests is associated with RH damage (Weylman et al., 1989). Other studies similarly suggest RH deficits in utilizing verbal and situational context to recognize conventional meanings. Brownell et al. (1986) found RH damaged subjects to be deficient in making the inferences required to interpret nonliteral meanings in texts. Furthermore, RH damaged patients are less able than normal subjects to use context to interpret humorous meanings in jokes (Brownell et al., 1983; Brownell and Gardner, 1988). Thus deficits in perceiving both the stereotyped form and the conventional meaning of nonliteral expressions have been associated wi th RH damage.

Although evidence for RH involvement in processing of nonliteral language is more convincing, the frontal lobes have also been implicated in the "abstracting" ability thought to be reflected in proverb interpretation (Cummings, 1985; Stuss and Benson, 1986). Only one study using proverbs could be found to support this notion. The study by Benton (1968) mentioned above, using the multiple choice portion of Gorham Proverbs Test, reported significantly worse performance in patients with bilateral frontal lobe damage, compared to patients with unilateral left or right frontal lobe damage. However, in that study, patients with right frontal damage performed somewhat worse (mean number correct of 20.1) than patients with left frontal lobe damage (mean correct of 26.4), again pointing to a special role of the RH in the management of proverbs. (Patients with posterior lesions were not included.) In his discussion of these results, Benton. (1968) notes that "an unexpected difference in the mean scores of the unilateral groups also appeared, the right frontal patients performing at a lower level than the patients with left frontal disease." He goes on to note that had the difference gone in the opposite direction, the results would be explained "by the circumstance that the test is a verbal task," yet analyses of individual subjects reveals that, overall, the LH damaged patients (n= lO) performed better than the RH damaged patients (n=8), with 4 of the 10 LH damaged group "earn(ing) scores that were above the highest score made by the right frontal patients." This result obtained nearly 25 years


ago, then difficult to explain, is compatible with contemporary evidence for the role of the RH in nonliterallanguage abilities.

Characterization of Nonliteral Language

It will be useful at this point to place our topic in its larger context. The larger set of familiar nonliteral language includes idioms ("She has him eating out of her hand," "The coast is clear"), proverbs ("Rome wasn't built in a day," "People who live in glass houses shouldn't throw stones"), slang ("get on the stick") and cliches, ("the pursuit of happiness"), social speech formulas ("How are you," "Say when," "Glad to meet you," "What '!- small world," "I'll get back to you later,") (Lyons, 1968), indirect requests ("Do you know what time it is?") (Clark, 1979), other conventional expressions ("There's always a first time," "I couldn't eat another bite"), and exclamations ("Fancy that!" "Do you mind?") including expletives ("God damn it," "Go to hell," "Son of a gun"). While a numeric estimate is difficult to come by, familiar language comprises a large proportion of normal communication, and familiar expressions are intricately woven into the fabric of propositional language (Bolinger, 1976; Jesperson, 1965; Tyler, 1978; Pawley and Syder, 1980). In an attempt to gather a list of familar nonliteral expressions routinely used in conversation, Fillmore (unpublished) catalogued nearly three thousand interactional speech formulas alone. More than 4000 commonly used expressions including slang, proverbs, idioms and cliches appear in "A Dictionary of American Idiom" (Boatner et al., 1975). Even more importantly, for a person to be judged as a fluent and competent speaker of a language, knowledge and appropriate use of nonliteral lan-guage is essential (Fillmore, 1979; Bolinger, 1976; Pawley and Syder, 1980). Yet this crucial aspect of language has received surprisingly little attention in the linguistic, neurolinguistic and clinical literature (see Chafe, 1968; Weinreich, 1969; Van Lancker, 1973, 1988; Hopper, 1989).

Familiar nonliteral language differs from propositional language in several ways. The defining property of propositional language is that it is constituted of grammatically organized sequences of words. Knowledge of grammatical rules and the lexicon makes it possible to produce and understand a potentially infinite set of sentences. In contrast, although superficially similar to propositional language, nonliteral expressions have unitary and cohesive form, rather than constituent structure (Lyons, 1968), and they make up a finite (although large) set. Both form and meaning are relatively fixed. It must be noted that some familiar phrases are more fixed (or cohesive) than other (Bolinger, 1976; Van Lancker, 1973; Pawley and Syder, 1980; Hopper, 1989; Gibbs and Nayak, 1989), and that in human language cohesion and conventionality in language are best conceived as occurring in degrees, or along the continuum from newly generated to entirely fixed, as discussed previously (Van Lancker, 1987). However, most idioms, proverbs and social formulas are learned, produced and compre-hended as entire units rather than as a sequence of grammatically indepen-dent lexical components. Knowledge of grammar and lexical meanings is


not necessary for successful processing of nonliteral expressions. In fact, applying that knowledge to an idiom or proverb will result in a wrong answer. Thus, stereotyped form and conventional meaning are the cardinal properties of most kinds of familiar nonliteral language. Unfamiliar nonli-terallanguage, such as newly created metaphors and other poetic usage, has very different properties from either literal or familiar nonliteral expres-sions, and would lead us into realms of human artistic expression and creativity about which even less is known.

A Brain Model of Nonliteral Language Processing

A brain model of nonliteral language processing must take into account usage of unfamiliar and familiar exemplars. It must distinguish between production and comprehension modalities, and it must recognize a distinc-tion between natural abilities (understanding and producing familiar nonliteral language "on-line") and additional metalinguistic abilities-those required for test-taking. As mentioned above, how and where poetic metaphor-the ultimate in unfamiliar nonliteral language-might be created and comprehended by the normal language user is much too great a question to ask here. One might speculate that both cortical hemispheres are involved, and a role of the corpus callosum in creativity has been proposed (see Bogen, 1969b).

For familiar expressions, it is likely that in natural language function, form and meaning are processed in the RH. The pattern recognition abilities of the RH (Bever, 1975; Bogen, 1969a; Bradshaw and Nettleton, 1983, Bryden, 1982) store and process the forms, while specialized abilities for contextual and semantic inference (Brownell et ai., 1986; Molloy et ai., 1990; Sidtis, et ai., 1981a, b) of the RH process the special, conventional meanings of familiar nonliteral expressions.

It is further likely that form and meaning in nonliteral language, both processed in the RH, are processed by different cerebral structures in that hemisphere. In normal language behavior, production abilities of nonliteral forms may be associated with anterior structures of the RH, whereas comprehension of nonliteral meanings is likely associated with the posterior RH. This model is based on analogy with the aphasias, whereby motor output is anteriorly programmed and comprehension is processed poster-iorly. As described above, studies by Van Lancker and Kempler (1987) and others have shown that comprehension of idioms and proverbs is strongly associated with RH function, but whether posterior sites are more specifi-cally involved remains to be confirmed.

Studies of natural production arc more difficult to design, but the evidence implicating frontal areas in production of nonliteral form de-scribed above for Alzheimer's speech is suggestive. As mentioned previously, in Alzheimer's disease, motor programs for familiar, nonliteral expressions are intact, despite disturbed comprehension of their meanings and despite disturbed output of propositional language. The preserved ability to pro-duce speech formulas may be attributable to intact frontal and/or fronto-


subcortical systems. In support of this view, Grafman (1989) includes the ability to engage in social communication in the set of abilities mediated by frontal lobes (p. 109). This model, namely, that RH mediates nonliteral language, with production and comprehension associated with anterior (subcortical) and posterior structures respectively, predicts that patients with Parkinson's disease who have advanced frontosubcortical dysfunction will be more impaired in production of nonliteral language forms than comprehension of conventional meanings, the inverse of dementia of the Alzheimer type.

Using this model for processing of familiar nonliteral language, the practice of clinical proverb testing as part of the mental status evaluation can be better understood. First, responses to an unfamiliar proverb or idiom are intrinsically difficult or impossible to assess. Secondly, it is not known where in the brain metalinguistic abilities to "define" are represented. Interpretation of familiar proverbs (whether using a free response or multiple choice format) utilizes the linguistic abilities of the LH as well as inferential abilities of the RH, managed by executive functions of the frontal lobes (Stuss and Benson, 1986; Grafman, 1989). From this perspec-tive, because multiple and diverse higher cognitive functions are called upon for optimum performance, (familiar) proverb testing provides a nonspeci-fic, nonlocalizing but highly sensitive probe of brain state and mental :;tatus.

Acknowledgements

I appreciate the many thoughtful comments and discussion on previous drafts of this article by William Beatty, PhD,joseph E. Bogen, PhD,jeffrey Cummings, MD, Daniel Kempler, PhD, Elliott Ross, MD, and john Sidtis, PhD.

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The Neurology of Proverbs · language (e.g. proverbs, idioms, speech formulas, and indirect requests) point to an important role of the right hemisphere (RH). Research describing