Laughter and electroencephalographic activity

The electrical activity of the brain shows rapid changes associated with Information processing. Waveform components within an event-related brain potential (ERP) triggered by a Stimulus are indicators ofsubsequent perceptual and cognitive processing. A positive wave at about 300 milliseconds (P300) following the presentation ofa Stimulus indicates the activity of categorization while a negative wave at about 400 milliseconds (N400) corresponds with a disruption and possible extension of the categorization process. This "incongruity" wave prompted speculation that similar neural activity might occur in humor. In apilot study one participant showed clear evidence of P300 and N400 over the whole cortex when responding to humorous Stimuli. A subsequent experiment attempted to manipulate the mood of additional subjects prior to the presentation of the humorous Stimuli. ERP activity was used to compare jokes that did or did not elicit laughter. Although the mood manipulation resulted in only weak and inconsistent subjective and behavioral changes, there was some evidence ofcortical changes. More significantly, jokes that did notproduce laughter showed no evidence of the N400 while those that elicited laughter did show this electrical pattern ofdisrupted categorization. Evidence from individuals with injuries to various parts of the brain shows that different areas of the cortex play different roles in mental tasks. The whole cortex, however, seems to be involved to some extent in complex Information processing. A high level skill that requires such complex thought is humor appreciation. Brownell and Gardner (1988) have reported that damage to the right cortical hemisphere leads to an acceptance of any incongruity äs funny. Humor 10-3 (1997), 285-300 0933-1719/97/0010-0285 © Walter de Gruyter 286 P. Derks, L.S. Gillikin, D.S. Bartolome-Rull, and E.H. Bogart Damage to the left hemisphere may cause an inability to comprehend the incongruity. The individual tends to take the story seriously. Lefthemisphere problems also cause the person to fail to distance from the aggression in humor and, consequently, not find it acceptable (Gillikin and Derks 1991). In reviewing numerous studies on Stimulation and Inhibition of the cortex, Sackheim et al. (1982) concluded that the right hemisphere is involved in depression and the left in elation. Thus the damaged right hemisphere leaves all incongruities funny and the damaged left hemisphere permits too much seriousness. More specifically, the functioning left hemisphere may be said to recognize the incongruity and the right hemisphere seems to try to find the pattern to resolve the Situation. The left cortex "sets up" the joke and the right "gets it" (McGhee 1983). This general cortical activity works through the pleasure centers of the midbrain and stimulates both the sympathetic and parasympathetic activity. Consequently, neuroendocrine responses could be initiated that might lead to the therapeutic effects of humor suggested by Cousins (1979; 1989). Berk et al. (1989) have supplied experimental evidence to support this position which has been outlined by Grumet (1989), amplified by Fry (1994), and criticized by Goldstein (1987). Much of this Information is, however, indirect and based on deficit. Techniques also exist for the direct examination of brain activity. Brain states have been determined that correspond to the categories of the Diagnostic and Statistical Manual of Mental Disorders (Third Edition revised) (John et al. 1988). Brain activity that matches various Information processing tasks has also been measured (Pope et al. 1995, Posner et al. 1988; Posner and Raichle 1994); however, few studies that directly measure neuroelectrical activity and humor appreciation have been reported. Svebak (1982) found that amused individuals showed less discordant alpha than people who were not amused. Since the nonamused individuals showed more alpha in the right hemisphere, indicating a relaxed state of the brain, it might be concluded that the "joke getting" part of the brain was resting or "bored. " More recently Bick (1989) reported that laughter on command increased alpha in the left hemisphere. In this case the joke may not be set up and the "rational hemisphere" more passive. These studies measured relatively long-term changes. Also of interest is the possibility of an immediate event-related response to incongruity and, perhaps, humor (McGhee 1983; Grumet 1989). Kutas and her associates (Kutas and Hillyard 1980; Van Fetten and Kutas 1990) have measured event-related potentials (ERP) and Laughter and electro 287 found a negative-going cortical activity at 400 milliseconds (ms) that corresponds to an incongruous word in a sentence. This "N400" followed a positive-going wave at 300 ms (P300) that indicated initial categorization of the Stimulus. This response to verbal materials shows the "setting up" of this incongruity (Coles et al. 1990). The initial demonstration of the N400 depended on anomalous sentence completions (Kutas and Hillyard 1980). Even slightly unexpected verbal Stimuli have been found to elicit the N400, though not to the same amplitude (Kutas and Hillyard 1984; Van Fetten and Kutas 1990). Nigam et al. (1992) have proposed that the N400 is more consistently related to any activation of conceptual memory. At least one study has reported that the amplitude of the N400 was related to the storage load in a memory search task (Mecklinger et al. 1992). Chwilla et al. (1995) found that the N400 was limited to a seniantic task. Another study, however, has presented ERPs that seem to show the N400 when errors in a simple discrimination task occur under instructions to be accurate rather than fast (Gehring et al. 1993). In any case, the N400 may be described äs occurring when categorization, usually semantic, is relatively unsuccessful and a search is initiated for better alternatives. The present study, then, investigated the neuroelectrical activity during the perception of incongruity and its resolution, i.e., during jokes and laughter. Since the semantic incongruity is inherent within a punchline, the N400 was expected äs the subject attempted to process the semantic violation.