Comprehension of metaphor and irony in schizophrenia during remission: The role of theory of mind and IQ
Introduction
In metaphorical and ironical speech, the actual meaning is not identical to the literal meaning, so the comprehension of non-literal language is different from literal language. For example, the understanding of metaphor and irony requires that interpreters go beyond the literal meaning of words to infer the intended meaning of statements (Sperber and Wilson, 1986, Sperber and Wilson, 1998, Seperber and Wilson, 2002). In recent years, studies that have included symptomatically acute and remitted patients have investigated their comprehension of metaphor and irony. Research has indicated that patients with schizophrenia have difficulty in the interpretation of metaphor and irony, but study findings have been inconsistent (Mitchley et al., 1998, Langdon and Coltheart, 2004, Herold et al., 2002).
Drury et al. (1998) found that schizophrenic patients who suffered from acute episodes of illness performed metaphor tasks, but not irony tasks, less competently than psychotic and depressed patients. Mitchley et al. (1998) found that patients with schizophrenia who were not in an acute episode of illness during test periods had specific difficulty in the understanding of irony compared with in-patient psychiatric controls. Herold et al. (2002) showed that remitted patients who had earlier suffered from acute paranoid schizophrenia, demonstrated statistically significant impairment in irony tasks, though not in metaphor tasks, as compared with normal control groups. Langdon et al. (2002a,b) investigated disturbed communication in schizophrenia and found that patients' understanding of irony and metaphor was selectively impaired relative to healthy controls. Symptomatic schizophrenic patients demonstrated a deficit in the comprehension of non-literal language, such as metaphor and irony. However, whether or not patients with schizophrenia can improve their understanding of irony and metaphor during remission was unresolved. The current study addresses this issue.
According to Sperber and Wilson, 1986, Sperber and Wilson, 1998 ‘theory of relevance’, the comprehension of non-literal language, such as metaphor and irony, not only involves semantic and syntactical decoding, but also requires non-linguistic inference. The appreciation of other mental states (e.g., knowledge, intention and belief) plays an important role in the understanding of speech content: for example, the understanding of irony requires an inference that a speaker's expressed intention is contrary to the surface meaning of the speech. The ability to infer and attribute mental states to others has been termed “theory of mind” (Premack and Woodruff, 1978) and is often assessed with the performance of first- and second-order false belief tasks (Wimmer and Perner, 1983, Perner et al., 1987). Happé (1993) demonstrated a strong theoretical relationship between theory of mind ability and an understanding of metaphor and irony. The ability to understand metaphor has been linked to a first-order theory of mind and the ability to understand irony has been linked to a second-order theory of mind. As metaphorical interpretation requires only limited understanding of a speaker's intentions, whereas ironical appreciation requires recognition of the speaker's understanding of a thought about the world, the comprehension of ironical speech requires a more sophisticated theory of mind ability than metaphoric speech (Happé, 1993, Happé, 1995, Longdon et al., 2002a, Langdon et al., 2002b). Colston and Gibbs (2003, Exp. 2) revealed that normal people draw second-order meta-representational inferences about a speaker's intentions and beliefs in the understanding of irony but not of metaphor. Langdon et al. (2002a,b) concluded that a disruption to normal adult mind-reading processes causes selective difficulties with the interpretation of irony in schizophrenic patients and that highly sophisticated normal adult mind-reading processes are not necessary for the interpretation of metaphor. Inhibitory control is required for both theory of mind and for the normal interpretation of metaphor and irony. The role of theory of mind in the understanding of metaphor and irony requires further examination.
Studies have indicated that patients with schizophrenia may exhibit a theory of mind deficit (Frith, 1992, Doody et al., 1998, Frith and Corcoran, 1996). Mazza et al. (2001) showed that chronic patients with normal IQs performed significantly less competently than normal controls in first- and second-order false belief tasks. Frith and Corcoran (1996) found that patients with schizophrenia in their remission group performed less competently than normal controls in second-order false belief tasks, but as competently as normal controls and psychiatric groups in first-order false belief tasks. They argued that patients with theory of mind deficits may make modest recoveries during remission (Frith and Corcoran, 1996). Pickup and Frith (2001) also found patients with behavioral signs and paranoid symptoms performed less competently than normal controls in first- and second-order theory of mind tasks, but that the remitted patients performed as competently as normal controls. Doody et al. (1998) concluded that an impaired theory of mind in second-order tasks is specific to schizophrenia when compared with mild learning disability and affective disorder control groups. Brüne (2003) found that patients with chronic disorganized schizophrenia were impaired relative to healthy controls in theory of mind tasks (e.g., first-order and second-order false belief tasks). In our study, we not only assessed theory of mind performance in remitted schizophrenia to compare findings with previous studies, but we also explored theory of mind in the comprehension of metaphor and irony in schizophrenia.
The role of IQ in the understanding of metaphor and irony warrants attention. Mitchley et al. (1998) demonstrated that even with Raven's IQ as a covariate, there was a significant difference between schizophrenic and control subjects who performed irony tasks. They argued that general intelligence cannot explain the inability of schizophrenic to understand irony. As patients often suffer from cognitive deficit and intelligence decline, it is difficult to completely match their IQs with those of normal controls. IQ may also influence a schizophrenic patient's theory of mind performance. For example, Brüne (2003) found that, when controlled for IQ, there was no theory of mind performance difference between patient's with chronic disorganized schizophrenia and healthy controls. Thus, we also examined the relative contribution of IQ to the understanding of metaphor and irony and a theory of mind in patients with remitted schizophrenia.
The purpose of this study was to investigate whether the ability to understand metaphor and irony in remitted schizophrenia among Chinese patients was impaired. It also aimed to examine the role of IQ and theory of mind in the understanding of metaphor and irony. We hypothesize that: (1) patients with schizophrenia are impaired in the comprehension of metaphor and irony as compared with healthy controls; and (2) in accordance with relevance theory and Happé's argument, a first-order theory of mind is correlated with the comprehension of metaphor and a second-order theory of mind is correlated with the comprehension of irony. If there is a specific deficit in a schizophrenic-patient's comprehension of metaphor and irony, then IQ does not significantly influence the comprehension of metaphor and irony.
Section snippets
Participants
Subjects composed 33 (17 males, 16 females) patients with schizophrenia and 22 (12 males, 10 females) healthy controls. The adults with schizophrenia were in-patients from Beijing's Anding Hospital and were assessed according to DSM-IV criteria (American Psychiatric Association, 1994). The patients determined to be in remission were assessed according to CCMD-3 criteria (Chinese Society of Psychiatry, 2001). Illness symptoms were mild or absent, while patients' scores on positive and negative
Performance on metaphor and irony tasks and theory of mind tasks
The descriptive data of participants' performance in all tasks are presented in Table 2. All participants gave correct answers to the control questions in the theory of mind tasks. Eighty-three and seventy-six percent of the patients gave correct responses in each of the first- and second-order false belief tasks. In the metaphor and irony tasks, the patients and the controls were able to retell the stories. Chi-square or t-test results showed that there were significant differences in the
Discussion
This study examined the comprehension of metaphor and irony in remitted schizophrenia as well as the role of theory of mind and IQ. The results showed that the comprehension of metaphor and irony in patients with remitted schizophrenia was impaired relative to healthy controls, and the impairment remained when IQ and verbal IQ were controlled for. This study also showed theory of mind deficits in schizophrenic patients during remission. The findings indicated that the comprehension of metaphor
Acknowledgements
This research was partially supported by a grant from the China Ministry of Education (01JAXLX014) and a National Science Fund of China (NSFC) project (30370201) to Yanjie Su and Research Initiation Fund to Raymond Chan. We are grateful to the individuals who participated in the study and to Professor Aimin Wang (Miami University, USA) for his helpful comments on earlier drafts of this manuscript. We also thank Miss Qian Wang (University of Illinois at Urbana-Champaign) for her editing
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