Humour experience in schizophrenia: relationship with executive dysfunction and psychosocial impairment

Humor processing and its relationship with clinical features in patients with first-episode schizophrenia

Humor, a higher-order social cognitive process unique to humans, is commonly impaired in patients with chronic schizophrenia. However, humor processing and its association with the clinical characteristics in the early stage of the illness remain unknown. In this study, we investigated humor processing and its relationship with clinical features in patients with first-episode schizophrenia (FES). We recruited 45 patients with FES and 44 healthy controls matched for age, sex, and education level. The participants completed the Picture Humor Processing Task (HPT-p) and Video Humor Processing Task (HPT-v), which evaluated humor comprehension and appreciation, and a questionnaire assessing their humor styles. Clinical participants also completed clinical and social functioning measurements. Signal detection theory analysis was used to calculate the d' and β values, which represent the detection of humor signals in the comprehension phase and inner criteria of the humor appreciation phase, respectively. In the HPT-p, patients with FES showed a higher false alarm rate (p = 0.048) than healthy controls, whereas the hitting rate, signal recognition ability (d' value), and intrinsic evaluation criterion (β value) were comparable between the two participants groups. In the HPT-v, patients with FES showed lower within-group coherence in the funniness rating (p = 0.023) than healthy controls. In addition, the false alarm rate in the HPT-p and negative symptoms effectively predicted social functioning in patients with FES (R2 = 0.681, p < 0.001). Our results indicate that impairment of humor comprehension in patients with schizophrenia is generated in the first episode and contributes to social functioning deficits, which require early recognition and intervention.

On the specificity of figurative language comprehension impairment in schizophrenia and its relation to cognitive skills but not psychopathological symptoms - Study on metaphor, humor and irony

People with schizophrenia have difficulty understanding figurative expressions, such as metaphors, humor or irony. The present study investigated the specificity of figurative language impairment in schizophrenia and its relation with cognitive and psychotic symptoms. It included 54 schizophrenia and 54 age and sex-matched healthy subjects who performed a cognitive screening (ACE-III) and figurative language comprehension task consisting of 60 short stories with three types of endings: a figurative one and its literal and an absurd (meaningless) counterparts. Each figurative domain - metaphor, humor, irony - was split into two sub-domains, i.e., conventional and novel metaphors, intended-to-be-funny and social-norm-violation jokes, simple irony and critical sarcasm, respectively. The main findings are: i) in schizophrenia, figurative language deficit manifests itself in each domain; ii) the most pronounced subdomain-specific impairment has been found for novel vs conventional metaphors and irony vs sarcasm; iii) altered figurative language comprehension was related to diminished cognitive abilities but not to psychopathology symptoms (PANSS) or other clinical characteristics. This may suggest that figurative language impairment, as a specific part of communication deficit, may be regarded as an essential characteristic of schizophrenia, related to primary cognitive deficits but independent of psychopathology.

Hypo- and hyper-activation in frontotemporal lobe during humor processing in patients with first episode schizophrenia

BACKGROUND

Patients with schizophrenia present difficulties in humor recognition and appreciation, but the neural mechanism of these deficits remains unclear. This study aimed to elucidate neural substrates underlying humor processing in patients with first episode schizophrenia (FES).

METHODS

This study recruited 40 patients with FES (illness duration ≤ 4 years) and 31 healthy controls matching for age, gender and education level. Participants completed a fMRI verbal humor processing paradigm comprising 96 stories, half for funny punch-line condition and the other half for unfunny condition. Participants were required to judge whether the story was funny or not. Signal detection theory (SDT) analysis was used to calculate d' and β values which represented sensitivity and inner criteria for humor signals respectively. The funny-unfunny contrast was analyzed to identify the brain regions related with humor processing. d' and β values were put into the imaging regression analysis.

RESULTS

Patients with FES showed significantly lower hit rate and sensitivity of humor signals (d'). At the neural level, patients with FES hypo-activated in ventral medial prefrontal cortex (vmPFC) and anterior cingulate cortex (ACC) while hyper-activated in middle temporal gyrus (MTG) and superior temporal gyrus (STG) compared to controls. In addition, activity in vmPFC and ACC was positively associated with d' and β values, while activity in STG was positively associated with β values in the clinical group.

CONCLUSIONS

Patients with FES exhibited decreased sensitivity to humor signals. Hypo-activation in frontal regions and hyper-activation in temporal regions were associated with the humor processing deficits.

The cognitive architecture of verbal humor in schizophrenia

Previous literature showed that people with schizophrenia have difficulties in humor comprehension and might differ from controls in the appreciation of humor, i.e., in perceived funniness. However, the cognitive architecture that underlies humor impairment in this population remains unclear, with humorous items sometimes assessed in the context of the communicative-pragmatic profiling and sometimes included in Theory of Mind (ToM) tasks. Here we enrolled 116 people with schizophrenia and 116 healthy controls, who were administered a task including jokes based on sound aspects and jokes based on mental aspects (Phonological and Mental Jokes task). Both comprehension accuracy (ability to select the funny ending of the joke) and appreciation (ratings of funniness) were evaluated, together with other linguistic, cognitive, and clinical measures. Results highlighted a diffuse impairment in humor comprehension in schizophrenia compared to controls, with mental jokes being more difficult for both groups. Humor comprehension was robustly associated with the patients' global pragmatic and linguistic profile, while the association with ToM was negligible. Another remarkable finding was the increased appreciation of humor in individuals with schizophrenia, who rated jokes (both correctly and incorrectly completed) as funnier than controls did. Funniness ratings were not predicted by any measure, pointing to a dimension untied from cognition or psychopathology. Overall, this study offers evidence - on a considerably large sample - of altered humor understanding and appreciation in schizophrenia, sketching a cognitive architecture where humor impairment stands together with communicative impairment, rather than with social cognition. This has implications not only for the assessment of humor, but also for how to treat it in patients to improve their ability to navigate the social world.

A meta-analysis of the associations between theory of mind and neurocognition in schizophrenia

Theory of mind (ToM) refers to the ability to infer the mental states of others. ToM is impaired in schizophrenia and these deficits seem to hinder functional recovery. ToM is thus an important, but complex treatment target, supported by several processes. A large number of studies report significant associations between ToM and neurocognition (e.g. memory, attention), but the neurocognitive domains that are most closely linked to ToM remain to be identified. A meta-analysis was conducted to estimate the magnitude of the associations between ToM and neurocognition in people with schizophrenia. Correlations were extracted from the relevant literature, transformed into effect sizes Zr and pooled as weighted means. Focused-tests were employed to test for differences between neurocognitive domains and for differences linked to the characteristics of ToM tasks. Ninety-one studies (N = 5462) were included. Moderate associations emerged between ToM and each neurocognitive domain (Zrs 0.27-0.43), with no significant difference between domains (χ2(8) = 11.89, p = 0.156). Within the domain of executive functions, abstraction showed a stronger association with ToM (χ2(4) = 18.93, p = 0.001). Several ToM tasks characteristics (e.g. modality of stimuli, type of mental state), were significantly related to the magnitude of the associations between ToM and executive functions, visuospatial/problem solving, attention and episodic memory. These results suggest that ToM is linked to a wide range of neurocognitive abilities in schizophrenia, and that ToM tasks are a significant moderator of these associations. The assessment and treatment of ToM should consider the neurocognitive profile of each patient to understand his difficulties and to tailor interventions.

Humor perception in schizophrenia appears to be related to disorganization syndrome

Perception of humor seems to be often disturbed in schizophrenia, yet current literature is limited and ambiguous on its relationship to psychopathology. A sample of 40 schizophrenia-diagnosed subjects provided humor comprehension and funniness ratings for 60 cartoons and 60 stories with funny, neutral and absurd punchlines. Disorganization syndrome was found to associate with deficits in humor comprehension and experienced funniness in non-humorous stimuli after controlling for cognitive performance, age, sex and medication. The findings are discussed in relation to previous studies on the topic.

Reduced synchronized brain activity in schizophrenia during viewing of comedy movies

Previous evaluation of brain function in schizophrenia has focused on standard experimental tasks, with cerebral response to natural stimuli less clear. This study employed inter-subject correlation (ISC) analysis to investigate the neural basis of humor processing during free viewing of comedy movies in patients with schizophrenia. We recruited 29 patients diagnosed with schizophrenia and 29 healthy, age- and sex-matched controls. Each participant underwent fMRI scanning during two viewings of three comedy movie clips. The ISC map from each participant pair within each population group and each movie viewing was separately derived. The significance of ISC within a group and between two groups were assessed by bootstrapping. The ISC map from each patient pair were also correlated with the product of Positive and Negative Syndrome Scale (PANSS) rating between the same participant pair in schizophrenia patients. Schizophrenia patients showed significant ISC in bilateral lateraloccipital, bilateral superior frontal, left supramarginal, and right lateralorbiofrontal cortices. Compared with the controls, the schizophrenia group exhibited significantly lower ISC in the left superior temporal sulcus, bilateral supramarginal, and bilateral inferiorparietal cortices. Higher clinical severity (higher total PANSS rating) was associated with lower ISC in the middle frontal and middle temporal regions, and also higher ISC in the visual cortex, inferior temporal gyrus, and anterior cingulate. The findings indicated that patients with schizophrenia are characterized by lower ISC in a frontal parietal network while viewing comedy film clips, which implicated a deficit in the cognitive component of humor processing. The lower synchronization in parts of the frontal parietal network also correlated with symptom severity.

Humour processing deficits in individuals with social anhedonia

Humour processing comprises the humour comprehension and the humour appreciation phases. Patients with schizophrenia have impaired humour processing. However, it is unclear whether such deficits affect subclinical populations such as individuals with social anhedonia. Our study recruited forty-eight individuals with high levels of social anhedonia (HSA, screened by the Revised Chapman Social Anhedonia Scale) and 50 individuals with low levels of social anhedonia (LSA). Participants completed behavioural tasks which tapped into humour comprehension and appreciation, and a set of questionnaires assessing their sense of humour, humour styles and subjective experiential pleasure. Using signal detection theory analysis, the d' and β values were generated to measure the detection of humour signal in the comprehension phase and the inner criteria of the humour appreciation respectively. The results showed that the HSA and LSA groups did not differ in humour signal detection (d') but the HSA group had significantly higher inner criteria of humour appreciation (β) than the LSA group. The β value was correlated with experiential anticipatory pleasure in all participants. The HSA group had significantly lower within-group coherence than the LSA group when processing humour. Our findings suggested that individuals with social anhedonia have impaired humour processing.

Frontal hypoactivation and alterations in the reward-system during humor processing in patients with schizophrenia spectrum disorders

Humor is a ubiquitous human ability with important implications for both social and emotional functioning. Patients with neuropsychiatric disorders, such as schizophrenia, experience difficulties in the comprehension and appreciation of humor. However, the specific neural mechanisms underlying these deficits are unknown. In the current study, we sought to elucidate the neural correlates of humor processing in patients with schizophrenia spectrum disorders (SSD). Functional Magnetic Resonance Imaging (fMRI) was used in thirty-one patients with SSD and a control group, performing a humor processing paradigm. Both regional brain activation and parametric modulation of brain responses via subjective funniness ratings were collected during the scanning procedure. On a neural level, large overlaps in fronto-temporal brain activation was found in both groups. However, patients compared to healthy control subjects showed attenuated responses in frontal brain regions, including the anterior cingulate cortex, medial prefrontal cortex (mPFC), superior frontal gyrus and middle frontal gyrus, as well as in the striatum (i.e. caudate nucleus, putamen). Furthermore, parametric modulation of subjective funniness ratings resulted in attenuated responses in the mPFC, bilateral insula, and left hippocampus. Analysis of functional connectivity revealed alterations in mPFC-caudate nucleus coupling in patients with SSD, which might reflect impairments in reward-related processing. Notably, alterations in mPFC-caudate nucleus coupling in patients were significantly associated to subjective funniness ratings. Our results extend previous findings demonstrating the relevance of frontal hypoactivation for humor processing impairments in patients with SSD and first point towards alterations in humor appreciation processes.

Trait Cheerfulness Does Not Influence Switching Costs But Modulates Preparation and Repetition Effects in a Task-Switching Paradigm

Many studies have shown the beneficial effect of positive emotions on various cognitive processes, such as creativity and cognitive flexibility. Cheerfulness, understood as an affective predisposition to sense of humor, has been associated with positive emotions. So far, however, no studies have shown the relevance of this dimension in cognitive flexibility processes. The aim of this research was to analyze the relationship between cheerfulness and these processes. To this end, we carried out two studies using a task-switching paradigm. Study 1 aimed at analyzing whether high trait cheerfulness was related to better cognitive flexibility (as measured by reduced task-switching costs), whereas Study 2 aimed at replicating the pattern of data observed in Study 1. The total sample was composed of 139 participants (of which 86 were women) selected according to their high versus low scores in trait cheerfulness. In a random way, participants had to judge whether the face presented to them in each trial was that of a man or a woman (gender recognition task) or whether it expressed anger or happiness (expressed emotion recognition task). We expected participants with high versus low trait cheerfulness to show a lower task-switching cost (i.e., higher cognitive flexibility). Results did not confirm this hypothesis. However, in both studies, participants with high versus low trait cheerfulness showed a higher facilitation effect when the stimuli attributes were repeated and also when a cue was presented anticipating the demand to perform. We discuss the relevance of these results for a better understanding of cheerfulness.

Neural circuit of verbal humor comprehension in schizophrenia - an fMRI study

Individuals with schizophrenia exhibit problems with understanding the figurative meaning of language. This study evaluates neural correlates of diminished humor comprehension observed in schizophrenia. The study included chronic schizophrenia (SCH) outpatients (n = 20), and sex, age and education level matched healthy controls (n = 20). The fMRI punchline based humor comprehension task consisted of 60 stories of which 20 had funny, 20 nonsensical and 20 neutral (not funny) punchlines. After the punchlines were presented, the participants were asked to indicate whether the story was comprehensible and how funny it was. Three contrasts were analyzed in both groups reflecting stages of humor processing: abstract vs neutral stories - incongruity detection; funny vs abstract - incongruity resolution and elaboration; and funny vs neutral - complete humor processing. Additionally, parametric modulation analysis was performed using both subjective ratings separately. Between-group comparisons revealed that the SCH subjects had attenuated activation in the right posterior superior temporal gyrus (BA 41) in case of irresolvable incongruity processing of nonsensical puns; in the left dorsomedial middle and superior frontal gyri (BA 8/9) in case of incongruity resolution and elaboration processing of funny puns; and in the interhemispheric dorsal anterior cingulate cortex (BA 24) in case of complete processing of funny puns. Additionally, during comprehensibility ratings the SCH group showed a suppressed activity in the left dorsomedial middle and superior frontal gyri (BA 8/9) and revealed weaker activation during funniness ratings in the left dorsal anterior cingulate cortex (BA 24). Interestingly, these differences in the SCH group were accompanied behaviorally by a protraction of time in both types of rating responses and by indicating funny punchlines less comprehensible. Summarizing, our results indicate neural substrates of humor comprehension processing impairments in schizophrenia, which is accompanied by fronto-temporal hypoactivation.

Do better communication skills promote sheltered employment in schizophrenia?

Alongside various psychopathological symptoms and neurocognitive dysfunctions, communication skill impairments may be considered core feature of schizophrenia. Although many studies examined the relation between employment status and neurocognition in schizophrenia, we still know very little about the role of communication skills in vocational status among people with schizophrenia. The purpose of this study is to identify the most characteristic communication, neurocognitive and social cognition differences which separate the employed schizophrenia outpatients from those who do not work. The study included three groups: 33 schizophrenia outpatients employed in social firms, 29 unemployed schizophrenia outpatients participating in occupational therapy and sex & age matched 31 healthy controls. We assessed communication skills, global cognitive functioning, executive functions, memory, social cognition as well as severity of psychopathology. Our results indicate that the most characteristic differences between employed and unemployed schizophrenia outpatients are associated with selective language and communication skills, i.e. paralinguistic aspects of communication, understanding of discrete meaning of linguistic context and figurative meaning of language. We find no significant differences between both clinical groups with regard to neurocognition and social cognition. Moreover, unemployed group had more severe psychopathology than the employed group, so we re-analyzed results controlling for symptom severity. The only differences that endured were related to general communication skills and explanation of pictured metaphors, but only when controlling solely for positive or negative syndrome. In conclusion, the present study indicates that employment in schizophrenia is associated with better symptomatic remission and communication skills, but not with better neurocognition and social cognition.

A preliminary investigation into theory of mind and attributional style in adults with grandiose delusions

INTRODUCTION

A preliminary cognitive model of grandiose delusions has been put forward suggesting that persecutory and grandiose delusions shared distinct, yet overlapping psychological processes. This study aims to test this model and hypothesises that participants experiencing grandiose delusions may demonstrate a theory of mind (ToM) impairment and differences in attributional style compared to a control group.

METHODS

A cross-sectional design compared the performance of 18 individuals with grandiose delusions to a control group of 14 participants with depression. ToM was measured using a non-verbal joke appreciation task and a verbal stories task. Attributional style was measured using the internal, personal and situational attributions questionnaire.

RESULTS

Participants experiencing grandiose delusions performed significantly worse on both ToM tasks compared to controls. Furthermore, these participants provided significantly more atypical answers when explaining the joke behind the ToM cartoons. No differences for subjective funniness ratings or attributional style were found.

CONCLUSIONS

This preliminary study indicated participants experiencing grandiose delusions have ToM impairments which may contribute to the maintenance of this symptom.

Investigating vision in schizophrenia through responses to humorous stimuli

The visual environment of humans contains abundant ambiguity and fragmentary information. Therefore, an early step of vision must disambiguate the incessant stream of information. Humorous stimuli produce a situation that is strikingly analogous to this process: Funniness is associated with the incongruity contained in a joke, pun, or cartoon. Like in vision in general, appreciating a visual pun as funny necessitates disambiguation of incongruous information. Therefore, perceived funniness of visual puns was implemented to study visual perception in a sample of 36 schizophrenia patients and 56 healthy control participants. We found that both visual incongruity and Theory of Mind (ToM) content of the puns were associated with increased experienced funniness. This was significantly less so in participants with schizophrenia, consistent with the gestalt hypothesis of schizophrenia, which would predict compromised perceptual organization in patients. The association of incongruity with funniness was not mediated by known predictors of humor appreciation, such as affective state, depression, or extraversion. Patients with higher excitement symptoms and, at a trend level, reduced cognitive symptoms, reported lower funniness experiences. An open question remained whether patients showed this deficiency of visual incongruity detection independent of their ToM deficiency. Humorous stimuli may be viewed as a convenient method to study perceptual processes, but also fundamental questions of higher-level cognition.

Validation of the Communication Skills Questionnaire (CSQ) in people with schizophrenia

This present study describes the validation of the Communication Skills Questionnaire (CSQ) in people with schizophrenia. A total of 125 clinically stable people in rehabilitation treatment who were diagnosed with schizophrenia were included. For convergent and discriminant validity the following tests were administered; the Gambrill and Richie (GR) Assertiveness Inventory, the Social Functioning Scale (SFS), Life Skills Profile (LSP), Clinical Global Impression scale for schizophrenia (CGI-S) and the Global Assessment of Functioning (GAF) scale. Internal consistency of the CSQ had a Cronbach׳s alpha of 0.96. Test-retest reliability showed coefficients between 0.60 and 0.70. Convergent validity showed significant relations at p<0.0001 for all instruments assessed. None of the subscales used for assessing discriminant validity showed a significant correlation with the CSQ except for the CGI-S depression subscale. The instrument shows good psychometric properties and demonstrates that it is a useful instrument for evaluating communication skills in people with schizophrenia.

Effectiveness of humor intervention for patients with schizophrenia: a randomized controlled trial

OBJECTIVE

The primary aim of this pilot study was to evaluate the possible therapeutic effects of a 10-session humor intervention program in improving rehabilitative outcomes and the effects of the intervention on patients' sense of humor among patients with schizophrenia.

METHOD

Thirty subjects were randomly assigned into either the intervention (humor skill training) group (n = 15) or the control (doing handwork) group (n = 15). The results were analyzed using descriptive statistics, t-tests and ANOVA.

FINDINGS

Repeated measures analysis of variance (ANOVA) tests were conducted to examine the differences across conditions and time. A group by time interaction effect was observed on all of the outcomes, except positive symptoms of PANSS. The time main effect was also significant on the total score (p < 0.005) and the negative symptoms score (p < 0.001) of the PANSS.

CONCLUSIONS

The implementation of humor skill training in a mental health service can improve rehabilitative outcomes and sense of humor for schizophrenia patients who were in the rehabilitation stage.

The neural basis of humour processing

Humour is a vital component of human socio-affective and cognitive functioning. Recent advances in neuroscience have enabled researchers to explore this human attribute in children and adults. Humour seems to engage a core network of cortical and subcortical structures, including temporo-occipito-parietal areas involved in detecting and resolving incongruity (mismatch between expected and presented stimuli); and the mesocorticolimbic dopaminergic system and the amygdala, key structures for reward and salience processing. Examining personality effects and sex differences in the neural correlates of humour may aid in understanding typical human behaviour and the neural mechanisms underlying neuropsychiatric disorders, which can have dramatic effects on the capacity to experience social reward.

Theory of mind skills are related to gray matter volume in the ventromedial prefrontal cortex in schizophrenia

BACKGROUND

Among individuals with schizophrenia, deficits in theory of mind (ToM) skills predict poor social functioning. Therefore, identifying the neural basis of ToM may assist the development of treatments that improve social outcomes. Despite growing evidence that the ventromedial prefrontal cortex (VMPFC) facilitates ToM skills among healthy individuals, methodological challenges, such as the influence of general cognitive deficits, have made it difficult to identify the relationship between ToM processing and VMPFC function in schizophrenia.

METHODS

We used voxel-based morphometry and a multi-method behavioral assessment of ToM processing, including performance-based (Recognition of Faux Pas Test), self-report (Interpersonal Reactivity Index, Perspective-Taking), and interview-rated (Quality of Life Scale-Empathy score) ToM assessments, to investigate whether ToM skills were related to VMPFC gray matter volume (GMV). Standardized neuropsychological measures were used to assess global cognition. Twenty-one schizophrenia and 17 healthy control subjects participated.

RESULTS

Between-group behavioral analyses showed that, as compared with healthy participants, schizophrenia participants had worse ToM performance and lower self-reported ToM processing in daily life. The between-group analysis of GMV showed that schizophrenia participants had less VMPFC GMV than healthy participants. Moreover, among schizophrenia participants, all three measures of ToM processing were associated with VMPFC GMV, such that worse ToM skills were related to less VMPFC GMV. This association remained strong for self-reported and interview-rated ToM skills, even when controlling for the influence of global cognition.

CONCLUSIONS

The findings suggest that among individuals with schizophrenia, reduced VMPFC GMV is associated with deficits using ToM skills to enhance social relationships.

Theory of mind and paranoia in schizophrenia: a game theoretical investigation framework

INTRODUCTION. Ample evidence already shows that theory of mind (ToM) is impaired in people with schizophrenia. Our aim was to critically review this literature. METHOD. We completed a selected review of the research literature on ToM in schizophrenia. RESULTS. Gaps in ToM research were identified. A specific relationship between impaired ToM and paranoid delusions, although intuitively reasonable from a theoretical basis, has only been demonstrated in a few studies. Psychometric properties of ToM tasks employed in these studies may be a confounding factor in drawing conclusions about the relationship. Because most ToM measures have focused on the third-person perspective, participants are not actively interacting. The tasks fail to capture the cognitive demands faced by individuals in real-life situations, and, in effect, are not a direct measure of ToM. CONCLUSIONS. Potential research areas are discussed. Since game theoretical paradigms require the direct involvement of the first person and situate the participant's interpersonal reasoning within an interactive context, they provide more ecologically valid experimental platforms than conventional questionnaire measures to assess ToM in schizophrenia research.

The use of humor in serious mental illness: a review

There is now a relatively good understanding of the broad range of direct and indirect effects of humor and laughter on perceptions, attitudes, judgments and emotions, which can potentially benefit the physical and psychological state. This article presents a review and discussion of the use of humor and laughter in treating people with serious mental illness, distinguishing between clinical papers on individual and group psychotherapy, and empirical research reports describing humor and laughter interventions. In spite of the exponential growth of the field over the last 30 years, I conclude that empirical studies are still lacking, the studies that do exist have major methodological shortcomings, and the field is in dire need of further investigation.

Diminished humour perception in schizophrenia: relationship to social and cognitive functioning

This study attempted to confirm that humour recognition deficits previously found in schizophrenia are specific to the condition and not attributable to other parameters such as depression or anxiety. Secondarily, we explored any possible cognitive or social functioning correlates to humour recognition deficits. A total of 60 participants (20 outpatients with schizophrenia, 20 psychiatric control participants and 20 control participants) underwent a 64-question humour task in addition to a battery of standard cognitive tests and Social Functioning Scales. In order to compare the three groups of participants, we conducted an analysis of variance (ANOVA) and post-hoc t-tests on neuropsychological measures, social functioning measures, and the primary outcome, humour recognition. The schizophrenia group showed significant and substantial deficits in humour recognition compared to the healthy control group, t(38)=5.1, P<0.001, ES=-1.55 and the psychiatric control group, t(38)=3.6, P=0.001. In the schizophrenia group, humour recognition correlated positively with general intellectual functioning (NART) r=.45, P=0.04, social reasoning (WAIS-III Comprehension) r=.54, P=0.01, executive functioning (WCST-CC) r=.69, P=0.001 and social adjustment ratings (SASS scores), r=.54, P=0.02. These findings support the assertion that humour recognition deficits in schizophrenia are specific to the condition and not attributable to other factors such as depression or anxiety. Furthermore, humour recognition deficits in schizophrenia may perhaps be preferentially associated with deficiencies in set shifting and semantic cognition.

Theory of mind impairment in schizophrenia: meta-analysis

There is now substantial evidence for Theory of mind (ToM) impairment in schizophrenia. Despite this, we know little about how dynamic (state) variables and broad clinical, cognitive and medication characteristics moderate the precise magnitude of the observed ToM deficit during task performance. Meta-analyses were conducted using 36 studies that reported continuous data regarding ToM performances of schizophrenia patients and healthy control subjects. These 36 studies included 1,181 (67% male) patients with schizophrenia and 936 (58.3% male) healthy control subjects. Individual analyses were also conducted for the Hinting and the Eyes tasks. The effects of moderator variables were studied by both subgroup and meta-regression analyses. The effect sizes (Cohen's d) for overall ToM performance and the individual tasks were large (d=0.90-1.08). In "remitted" patients, the degree of ToM impairment was less pronounced than non-remitted patients (d=1.21) but it was still significant (d=0.80). Moreover, the distribution of effect sizes was more homogeneous for the individual tasks, especially in "remitted" patients. General intellectual deficits observed in schizophrenia patients contributed to their ToM impairment only in the remission phase of the illness. While state variables and task specific differences explain a large degree of the heterogeneity of the ToM findings observed in previous studies, the persistence of ToM deficits in "remitted" patients suggests there are trait related mentalising impairments in schizophrenia. Our review also suggests that future research should consider the potential moderating influence of IQ deficits on ToM performance in "remitted" patients, as well as the potential effects of residual symptoms.