HUMOR, TICKLE, and PAIN Facial Expressions, Smile Types, and Self
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Facial Expressions 1 Running head: HUMOR, TICKLE, AND PAIN Facial Expressions, Smile Types, and Self-report during Humor, Tickle, and Pain: An Examination of Socrates’ Hypothesis Christine R. Harris Psychology Department University of California, San Diego Nancy Alvarado Center for Human Information Processing University of California, San Diego Author Contact: Christine R. Harris, Ph.D. Department of Psychology - 0109 University of California, San Diego La Jolla, CA 92093-0109 Phone: (858) 822-4507 Email: [email protected] Word Count (main text and footnotes): 4028 Facial Expressions 2 Key words: emotion, facial expressions, laughter, humor, pain, tickling Facial Expressions 3 Abstract The nature of ticklish smiling and the possible emotional state that accompanies it have been pondered since the ancient Greeks. Socrates proposed that tickle induced pleasure and pain. Others, including Darwin, have claimed that ticklish laughter is virtually the same as humorous laughter. The present study is the first to systematically examine facial behavior and self-reports of emotion in response to tickling. Using a within-subjects design, 84 subjects’ responses to being tickled were compared to their responses when experiencing a painful stimulus and their responses to comedy. Overall results for both self-report and facial action coding showed that the tickle condition elicited both pleasure and displeasure. Facial action during tickling included “Duchenne” smiles plus movements associated with negative emotions. Results suggest that tickle-induced smiling can be dissociated from positive affect. Tickle may be a type of complex reflex or fixed-action pattern. Facial Expressions 4 Facial Expressions, Smile Types, and Self-report during Humor, Tickle, and Pain: An Examination of Socrates’ Hypothesis Tickling and the smiling it induces, at first blush, seem like child’s play. However, tickle, along with crying and startle responses, falls into the category of poorly understood affective phenomena. One intriguing aspect of tickle is that a physical stimulus can elicit a response that appears to closely resemble that of humor. The apparent similarity of the smiling and laughter induced by tickle and by humor has led many writers to assume that the two reflect the same internal state. One champion of this view was Charles Darwin (1872), who noted that “the imagination is sometimes said to be tickled by a ludicrous idea; and this so-called tickling of the mind is curiously analogous with that of the body” (p.199). Darwin described several similarities between tickle and humor. First, he claimed that a pleasant hedonic state was necessary to elicit laughter: “in this case, [humor] and in that of laughter from being tickled, the mind must be in a pleasurable condition; a young child, if tickled by a strange man, would scream in fear” (p.199). Second, he noted similarities in the elicitor of both states, “The touch must be light” in tickle and “an idea or event must not be of grave import” in humor. Finally, he pointed out that an element of surprise is required to elicit laughter to jokes or to tickle. In essence, tickle was simply a physical joke. Much contemporary writing on the topic echoes the view that ticklish laughter and smiling is the result of a positive affective state (e.g. Keith-Spiegel, 1972; Panksepp, 2000; Weisfeld, 1993). In contrast, Francis Bacon (1677) proposed that when tickled “men even in a grieved state of mind, yet cannot sometimes forbear laughing” (p. 151). This view suggests that ticklish smiling and laughter can be dissociated from a humorous state. Moreover, Bacon suggested that “tickling is ever Facial Expressions 5 painful, and not well endured” (p.161). The possibility that tickle elicits an unpleasant state was noted as far back as the ancient Greeks. Socrates suggested that tickling elicited pleasure but to a greater degree pain (cited by Gregory, 1924). Despite centuries of speculation, only a handful of empirical studies have investigated tickle, most within the past few years. For example, neuroscientists have employed light tickling in fMRI studies to explore the neural activation of anticipation of sensory stimuli (Carlsson, Petrovic, Skare, Petersson, & Ingvar, 2000; Blakemore, Wolpert, & Frith 1998). The remaining researchers have focused on trying to understand the nature of tickle.1 Observations such as those by Bacon have led some to propose tickle-induced smiling may have little to do with a positive emotional state such as amusement or happiness. Instead the tickle response may be a type of complex reflex or fixed action pattern (e.g. Black, 1982; Harris, 1999; Stearns, 1972), or perhaps a species-typical stereotyped motor pattern that requires a particular releasing stimulus (Provine, 1997). Recent findings provide some support for this view. First, while previous work has shown a warm-up effect of humorous stimuli (the first few jokes in a series are not as funny as later jokes), warm-up does not seem to transfer between humorous stimuli and tickle (Harris & Christenfeld, 1997). Second, ticklish laughter and smiling does not require the belief that another person is performing the tickling. Responses were as intense when people were alone and believed they were being tickled by a machine as when they were being tickled by another person (Harris & Christenfeld, 1999). Third, in Pavlovian conditioning, tickling has served as the unconditioned stimulus that elicits laughter (Newman, O’Grady, Ryan, & Hemmes, 1993) and tickle-induced smiling emerges in infants even when it has been not paired with playful interactions (Leuba, 1941). Facial Expressions 6 Despite this burgeoning interest in tickle, several questions remain unanswered. What is the connection between the facial expression of tickle and the internal subjective state? Is the smiling elicited during tickling completely disconnected from the internal emotional state as suggested by Bacon and advocates of a reflex explanation? Is the facial expression a mixture of pleasure and pain as claimed by Socrates? Do people who find tickle pleasurable display different facial expressions than those who find it unpleasant? Present Research The aim of this study was to explore these basic questions. The speculation that the tickle response is due to amusement has been based primarily on the assumption that the smiling that occurs during tickling is indeed the same as that occurs during humor. However, while only four of the studies described above specifically measured smiling/laughter during tickling; none of them closely examined these nonverbal displays to determine whether they differed from those evoked by humor. This study offers the first microanalysis of the facial movements that occur during tickling. It also systematically examined the emotional state that people reported experiencing during tickling, an aspect neglected in previous work. A within-subjects design was used to examine behavior and self-reported emotional responses of 84 subjects across three conditions: (1) being tickled for 10 seconds, (2) listening to a series of recorded comedy routines, and (3) immersing one hand in a bucket of circulating cold water for as long as tolerable. Comparing the facial expressions and self-report of the experience of tickle is of interest in its own right, and may shed light on the previously mentioned hypotheses regarding the nature of tickle. Including painful and humorous conditions enables us to examine whether tickle simply resembles amusement or has painful or unpleasant aspects. Facial Expressions 7 Method Subjects Eighty-four healthy University of California, San Diego students (61 females), who had not taken pain medicine, participated to fulfill a class requirement. Procedures Each subject participated alone and was exposed to three conditions: tickle, comedy, and pain. Order was counter-balanced across subjects. After each condition, the subject filled out an emotion inventory. Facial behavior was recorded by a videocamera placed in front of the subjects. Only the lens of the camera was exposed; the rest of the camera was hidden behind a large board, which contained colorful pictures. Tickle Condition. The female research assistant stood behind the subjects and tickled them on their sides (from the armpits to the waist) for 10 seconds. Subjects were informed that they could stop the tickling if the sensation became too intense. No subject asked to stop. Comedy Condition. Subjects listened to an audiotape of a series of twelve jokes by various comedians (e.g. Seinfeld, Cosby). The first 2 jokes were used as practice stimuli. Pain Condition. The subject’s left hand was immersed in a bucket of circulating cold water (1-5 Cº). Subjects were instructed to press a button when they first started to feel pain and then to press it again when they could no longer tolerate the pain, at which point they withdrew their hand from the water. If the subject had not pressed the intolerable pain button after 3 minutes, the experimenter terminated the task. One subject continued for the entire 3 min. Facial Expressions 8 Dependent Measures Facial Action Coding. Subjects’ facial movements were coded using Ekman and Friesen’s Facial Action Coding System (FACS; 1978). FACS provides a method for objectively describing movement in the face. It catalogs distinct combinations of observable muscle movements into 44 numbered appearance changes called “action units” (AUs). Ten seconds of facial behavior were coded during each condition as follows: the 10 sec during tickling, the 10 sec immediately before removing the hand from the cold water; and one second following each of the punchlines of the ten jokes (a total of 10 sec). Self-report ratings. After experiencing each condition, subjects described their subjective states using a series of rating scales labeled with the names of emotions and feelings. They used a scale of 0 (not at all) to 7 (extremely) to rate how much they had felt: anxious, happy, angry, embarrassed, and amused. They similarly rated how much they found the experience unpleasant and painful.