Impairments of humour comprehension in multiple sclerosis

Sociocognition is an important field of neuropsychology involving human interactions. In relapsing-remitting multiple sclerosis, it was recently demonstrated that sociocognition is severely and precociously impaired. Among sociocognitive abilities, humour has not yet been considered in this disease despite its important social functions, including during doctor-patient communication. Its main functions are to reduce stress when interactions become strained and to convey difficult messages in a gentle form. Thus, the inability to perceive this second degree of language is likely to generate a major social handicap. As humour is a higher cognitive process, its assessment requires the control of lower levels according to a serial model.

The present humour comprehension protocol, based on a serial cognitive model, consisted of a first incongruity detection step (normality identification task) and a second incongruity resolution step (funniness identification task). This protocol was administered using both verbal and visual material (stories and cartoons). For each type of material, the participant had to decide which of three proposed endings was normal (normality identification) and which was funny (funniness identification). A group of 21 relapsing-remitting multiple sclerosis patients was compared to a control group of 38 healthy participants. In view of the severe impairment demonstrated for MS patients in other sociocognitive abilities, we predicted a deficit of humour comprehension in these patients in comparison with healthy participants. In reference to the serial model of humour, and considering the variability of MS lesions, our main goal was to test the hypothesis of a primary deficit in incongruity resolution (selective to funniness identification) in some MS patients whereas others may suffer a non-specific comprehension impairment (affecting both normality and funniness identification).

Group analyses (non-parametric tests, Mann-Whitney) revealed lower scores for relapsing-remitting multiple sclerosis patients compared to controls for the visual tasks (normality and funniness). No significant difference was found in the verbal tasks. At the individual level, 62% of relapsing-remitting multiple sclerosis patients showed impairment compared to controls for the funniness tasks. Moreover, 38% presented a selective deficit in the funniness tasks.

These preliminary results suggest that a high proportion of relapsing-remitting multiple sclerosis patients may be impaired in humour comprehension, some as a primary deficit and others as a secondary deficit to more general comprehension difficulties. On a theoretical level, the dissociations obtained between verbal and visual material do not support an amodal humour comprehension model.