Differential Prosocial Behaviour Without Altered Physical Responses in Mirror Sensory Synesthesia

Transcription

1 Differential Prosocial Behaviour Without Altered Physical Resonses in Mirror Sensory Synesthesia Kallioi Iouma 1 Suervisors: Rob van Lier 1, Tessa M. van Leeuwen 1, Sarah Graham 2 1 Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, The Netherlands 2 Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands synesthetes mirror the ain or touch that they observe in other eole on their own body. It has not been Previous studies have yielded contradictory evidence on whether mirror sensory synesthetes demonstrate sensory synesthesia. We hyothesised that synesthetes would show more emathic and altruistic behaviour and enhanced theory of mind, and that this would relate to the hysiological and rating resonses to arousing ictures. We diagnosed mirror-sensory synesthetes with an established touch-interference aradigm and heart rate, skin conductance, and uil dilation were recorded. Cortisol levels were assessed. Altruism was tested with a one shot Dictator s Game where articiants divided money between themselves and a second layer. Questionnaires on emathy, theory of mind, ersonality traits, and ain ercetion were comleted. Eighteen mirror-sensory synesthetes and 18 controls articiated. Our results show that mirror sensory synesthetes are more altruistic and more strongly imacted by ositive and negative images. The stronger the but makes mirror-sensory-synesthetes develo ersonality characteristics similar to synesthetes of other the emathy measures, highlighting the need for further investigation on the hyothesis. Keywords: mirror sensory synesthesia, emathy, altruism, theory of mind, stress Corresonding author: Kallioi Iouma; iouma.k@gmail.com 25

2 Kallioi Iouma sensory stimuli leading to unusual, additional exeriences. One of the most common examles is graheme-colour synesthesia, where, for instance, the black written letters of a text would have a general oulation and there are three main asects First, the exeriences are elicited by articular stimuli that would not evoke such exeriences in most members of the oulation; the inducing stimuli can be ercetual or concetual. Second, the concurrent exeriences are automatic, involuntary nature of the synesthetic exerience is similar to that of a conscious ercetual event. It has been found that synesthesia is more common among eole (as if they were looking in a mirror, a secular Mirror sensory synesthesia has been related with enhanced emathic behaviour (Banissy & the general oulation, making it one of the most common forms of synesthesia, along with for its cause rooses increased activity in the tactile mirror system above a threshold for conscious tactile ercetion in synesthetes of this tye, causing observed tactile ercetion to be consciously region of anterior insula (Blakemore, Bristow, Bird, rocessing, seems to lay an imortant role along with rimary and secondary somatosensory cortex, common such as enhanced creativity, better memory for verbal material and oenness to exerience is heritable and that there are genetic comonents Emathy, altruism and theory of mind in mirror sensory synesthesia Mirror sensory synesthetes have been shown synesthesia inherited from generation to generation does not necessarily need to be the same (Barnett et imlicated and candidate genes suggested but there is no clear indication about the exact genetic cause The Mirror Sensory tye In this study we focused on the subtye Mirror Sensory Synesthesia, which is characterised by the roduction of conscious exeriences similar to another erson s observed state. Synesthetes of this tye, when seeing or imagining someone else being in ain or being touched, feel the sensation like it would be on their own body (Banissy & Ward, that often co-occur, one for the exerience of each case, synesthetes feel the observed sensation on their own body, localised at the same sot. For some synesthetes an observed touch on the left cheek triggers a synesthetic sensation on their left the synesthetic sensation is felt on the right cheek feelings of symathy and a desire to relieve another s suffering. After witnessing someone else s distress, unleasant emathic arousal can motivate the observer to hel the other in order to reduce his or her own distress and feel relieved as heightened emathy would be exected and logical as individuals exerience on their own body any unleasant sensation observed on others. Thus they would be more sensitive to the misfortunes of others and would be more willing to relieve their suffering. However, a recent study by Baron-Cohen between synesthetes (N enhanced emathic behaviour demonstrated by initial studies was due to their small samle sizes (N N relevant for mirror-sensory synesthesia. It refers to the ability to attribute mental states to other eole

3 EXPLORING MIRROR SENSORY SYNESTHESIA and make sense of their behaviour (Premack & can understand that others have beliefs, desires, intentions, and ersectives that are different from one s own and can make redictions about them. It is considered as a form of social intelligence and overlas with the term emathy as the latter can be seen as a secial form of simulation (Baron-Cohen & the emathy debate for mirror sensory synesthesia, in our study we asked our articiants to comlete emathic behaviour. In an attemt to quantify this henomenological sensitivity to the environment we asked mirror sensory synesthetes to comlete the Emathy is considered to be one of the main reasons why eole adot an altruistic behaviour could be considered as a trait co-inherited with in mirror-sensory synesthesia has not yet been established, but might be exected on the basis of the reorted heightened emathy ratings. In this study we also wanted to exlore this ossibility. Conclusions about human altruism can be drawn by observing human behaviour after natural disasters, in everyday life or through simulations of everyday situations. To stimulate emathic or altruistic behaviour in the laboratory, economical games based on game theory are being used have been used. The basic idea involves one layer dividing a sum of money between him- or herself and a second layer who is either able to accet or send his or her own amount to unish layers, The behaviour of eole who deny small offers in the ultimatum game, give big amounts of money in the Dictator game, or unish unequal sharing, The observed differences do not have to do with altruistic behaviour in mirror sensory synesthesia we asked from our articiants to lay a one shot Dictator s game. Physical reactions when exeriencing mirror sensory synesthesia Exeriencing mirror sensory synesthesia could be unleasant when synesthetes observe others in a ainful situation. Peole resond to challenging situations with changes in their behaviour and autonomic and neuroendocrine arameters, aimed at recovering the disturbed homeostasis. The concet of stress refers to the hysiological mechanisms resonsible to maintain and restore the balance after such changes. One of the main stress-coing strategies involves alterations of release of glucocorticoids such as cortisol (Munck, biochemical analysis of salivary cortisol is a good reresentative of the lasma or serum levels of Physiological resonses like heart rate, uil dilation a good indication of stress resonses (Bradley, aimed to test whether unleasant synesthetic exerience could elicit a hysical stress resonse in mirror-sensory synesthetes. If that were the case, it would be worth investigating whether the strength of the bodily stress resonse would correlate with how emathic a synesthete would be. In order to test that, we asked our articiants to rate ictures with arousing negative context while measuring their heart rate, uil dilation and skin conductance. Cortisol levels were also assessed as an additional measure for stress. Pictures with arousing leasant context were also shown so it could be checked if synesthetes would be more affected hysically by them too. Our articiants also comleted the behaviour. In this way we could examine whether their synesthesia causes deressive symtoms. If that would be the case, differential rates in emathy and in the rest of our measures could have been a result of this deressive behaviour. Aroach In this study we characterised the emathic behaviour, altruistic traits, theory of mind, and stress resonses of mirror sensory synesthetes. We hyothesised that eole with mirror sensory synesthesia would be likely to score higher on tests assessing emathic-altruistic behaviour and theory of mind. Moreover, individuals with mirror sensory 27

4 Kallioi Iouma synesthesia might develo higher cortisol levels, have larger hysiological resonses and be more affected while viewing ictures with arousing context. In order to address these questions, we assessed hysiological resonses (heart rate, uil dilation synesthetes were watching ictures with leasant, unleasant and neutral context. Mirror-sensory synesthetes were diagnosed with an established behavioural interference aradigm (Banissy & Ward, of mind were comleted and a one shot Dictator s game was layed to assess altruistic behaviour. It has not been studied so far whether mirror-sensory synesthesia could result in an altered ain ercetion in synesthetes of this tye. In order to address this question we asked mirror sensory synesthetes to synesthesia, there was no mirror sensory synesthetes taking art. Thus, we asked our articiants to in the effect of this tye of synesthesia. Exloratory analyses for all questionnaires were erformed. Particiants 28 Methods Synesthetes were recruited through synesthesia associations and announcements in the media. Control articiants were recruited through the university latform for recruiting articiants announcements at various locations. We interviewed the eole who contacted us via s, asking whether they exerienced mirror they had exerienced it all their life, and whether the exeriences were consistent and stable over time. We also asked about their age and overall health condition. Only synesthetes exeriencing the observed ain or touch on their own body at the same location as in the observed situation were invited to our laboratory. Some individuals were excluded due to severe comorbid disorders. In our (M age SD M age SD = 1 did not have any gender exclusion criteria during articiants recruitment. The grous did not differ in age (t information about the study rior to articiating and gave informed written consent to the study. Ethics aroval was obtained from the local Ethics Laboratory exeriments During their visit to the laboratory, articiants comleted two behavioural exeriments and a oneshot Dictator s game. The total duration was 2 hours. viewed ictures with a negative, ositive or neutral context and ictures of emotional faces of either a negative or ositive context while their heart rate, skin conductance and uil dilation were recorded to monitor stress resonses for each icture. After the resentation of each icture, they were asked to give a rating on how leasant or arousing they found it. Because this exeriment was hyothesized to affect the overall mood and stress resonse of the articiants, saliva samles for cortisol assessment were collected before and after the exeriment, and a mood questionnaire was comleted before and after the exeriment. There were maximally two time slots to circadian rhythm effects (Kudielka, Schommer, The urose of the second exeriment the Mirror Touch synesthesia tye. We used an reort the real touch that they received from an electrical device while watching videos of other Differences in the error rates and reaction times between synesthetes and controls allowed for the diagnosis of Mirror Touch Synesthetes. Finally, articiants comleted an exit questionnaire with questions about how they felt during each art of the exeriment, and layed a one shot Dictator s game to assess altruistic behaviour. We now turn to each exeriment in detail. Exeriment 1 - Reaction to arousing ictures In this exeriment, articiants were asked to rate arousing ictures on a scale from 1 to 9 for arousal and valence using the Self-Assessment

5 EXPLORING MIRROR SENSORY SYNESTHESIA Fig. 1. At the same time, hysiological resonses (heart rate, Stress resonses and mood alterations induced by this exeriment were additionally assessed. Before leaving the laboratory, articiants also rated the intensity of synesthetic ain and the synesthetic touch that they exerienced during this art, on a Stimuli. There were four stimulus categories: ositive, negative, neutral and emotional ictures. The emotional condition included two subcategories of ictures with faces of ositive and negative or being cut with a knife. In the ositive category ictures of eole exeriencing leasant sensation of touch were included, such as holding hands or touching soft materials. Neutral ictures reresented individuals erforming everyday tasks like washing dishes or reading. Reresentative ictures for these three categories are illustrated in Figure 1. Finally, the emotional ictures included eole with either For the stimuli that we created ourselves, valence and arousal ratings were not yet available, SAM scales for valence and arousal. Stimuli were included ictures with a valence rating (derived from M negative = SD M ositive = SD M neutral SD M emotion_neg SD = 1.2 for the emotional negative condition and M emotion_os SD = 1 for the emotional ositive condition. Subjective ratings. Each icture was initially this time assed, the SAM scale for valence aeared below the icture. Particiants had to tye a number from 1 to 9 and ress enter. After that, the SAM scale for arousal would aear and the articiant had to comlete it in the same way. If the overall duration of the trial at that oint would be less than In the case that after the second rating the trial would trial would start right after the second rating. This counterbalanced for landscae-ortrait analogies and for the sex of actors across conditions, and it was ascertained that the luminance of the ictures the International Affective Picture System ( the rest were created by us. of each icture was imortant for the hysiological resonses measurement as skin conductance needs this amount of time to get back to baseline. Before the actual exeriment, articiants had the chance to familiarize themselves with the task chin rest was used and articiants were instructed to move as little as ossible in order to avoid motion artifacts in the hysiological measurements. 29

6 Kallioi Iouma Physiological resonses. Heart rate, skin conductance and uil dilation were recorded for the duration of the entire exeriment. Heart rate were measured with the BioPack Student Lab heart rate measurement, three electrodes were used. Two of them were laced on the articiant wrists and one on the right ankle. For the skin conductance average, M SD each articiant. We statistically comared the uil icture onset, when the uil dilation had stabilised after the initial resonse to the change in luminance at the touching oints to facilitate the conductance of ions. For the uil dilation assessment, the Heart rate during the resentation of the ictures articiant. Data were analyzed using routines built from icture onset until icture offset. Trials on seconds during icture resentation were excluded from analysis. ECG data for the remaining trials were detrended and the eaks detected in order to calculate the number of beats er minute. On average, M = SD Three synesthetes and one control were removed after cleaning. We statistically comared the heart seconds from icture onset for each exerimental condition and between synesthetes and controls. The eak of the skin conductance resonse was statistically comared across conditions and articiants. Data were analyzed using routines built changes in skin conductance were comuted as the difference between the amlitude of the eak and the value at the beginning of each trial. Trials on analysis. Relative uil dilation was determined for each condition and each articiant by dividing the uil dilation at each moment during the stimulus eriod Cortisol measurements. Saliva samles for obtaining cortisol levels were collected at two time oints during the laboratory visit and one more time took lace right before the start of Exeriment 1 induction of stress we considered that as the best ossible moment for the second measurement, since Before arriving at the laboratory, articiants had already received instructions for the cortisol samling. In order to minimize differences in baseline cortisol levels, we instructed them not to brush their teeth, eat or drink anything but water for 1 hour before and to refrain from drinking alcohol, exercising, and smoking for 12 hours as was instructed by the In order to gain a baseline measurement of to erform an additional saliva collection at their home several days after their articiation in the exeriment. They received a saliva collection tube along with detailed instructions on how to use it during their visit to our laboratory. The saliva collection was done at the exact same time as the the saliva collection tube was mailed back to us via ost. The same restrictions regarding food intake etc. were alied as during the lab visit. Saliva was collected using the commercially available device of Salivette, Sarstedt. Particiants their mouth and chew gently on it for 1 min until it got humid. Then they laced it back in the Salivette until analyzed. The samles were sent to Dresden dilation during a 1 second re-stimulus baseline (-1 30

7 EXPLORING MIRROR SENSORY SYNESTHESIA Mood State. As we hyothesised that the arousing ictures in Exeriment 1 might affect the articiants mood, the mood state of the articiants was assessed using the Positive and the extent to which they exerienced each one of This measure was used at three time oints: two times at the laboratory and one at the articiant s home at the same time as the cortisol baseline saliva took lace right after the articiant s arrival and the otential alterations in the articiants mood due to the resentation of arousing ictures could be detected. Exeriment 2 Diagnosis for Mirror sensory synesthesia In this exeriment, articiants were asked to reort the location of actual touch (left, right, both, for touch felt at both sides and down for no feeling and error rates were recorded. For synesthetes, during a congruent trial the touch was delivered to the same side of the face as the synesthetic exerience. An examle of an incongruent trial would be, receiving an actual touch on the right cheek but due to a synesthetic exeriencing the feeling as being touched on the left cheek as well. In this case the correct answer would be right and a mirror touch error would be answering both. An examle of a no touch trial would be not receiving any actual touch from the device but observing touch in the video. This condition is hard for a synesthete exeriencing the observed touch on his or her body whereas a control can easily rely none. Previous research has shown that synesthetes tend to get confused during the incongruent and no touch trials in this tye of set-u. They make more errors and have longer reaction times than controls. They also seem to be faster at detecting congruent than incongruent touch in eole and congruent being touched. This is an established aradigm for diagnosing mirror-sensory synesthesia (Banissy laboratory articiants also rated the intensity of synesthetic touch that they exerienced during this Set u. Each video showed a boy, a girl, or an ale in one of the following conditions: touch on the right side, touch on the left side, touch on both sides, no touch. At the same time a tactile device alied real touch (left, right, both sides, was erceived as congruent (observed touch same touch, also felt the synesthetic touch on their face, which was the same as what was shown in the video. For otential synesthetes, congruency (secular or after the resentation of ictures involving touching scenes. The tactile stimuli from the device were alied simultaneously with the ones in the videos. Particiants had to reort the location of the real touch by ressing one of the keyboard arrow keys (left for left felt touch, right for right felt touch, u Before the actual exeriment, articiants had the chance to familiarize themselves with the task block, articiants had a break where they could move freely and the white noise, which was layed during the whole block to cancel the sound of the tactile device, was switched off. During the break for cortisol level assessment took lace. Data were analyzed using routines built inwith RTs that were above or below 2 SD from the in the RTs was not different between the two grous (F Stimuli. were used for each articiant. For each one of involved observed touch to an ale. The order of trials was randomised in three blocks. In our initial one synesthete reorted feeling a sensation of 31

8 Kallioi Iouma Fig. 2. with the touch alied from a lastic stick similar to the tactile device to reduce the covariant factors. differences were observed in their results. give their resonse while the video was still being layed. The next video would only start after a Tactile device. The tactile stimuli were administered via an electrical device made in house. The touch was delivered via two lastic arts (one the face. The lastic arts were attached to a surface suorted by a microhone suorting rod. White noise was layed via headhones during the whole exeriment, so articiants could not determine the location of the real touch due to mechanical noise of the device. In order to revent the articiants from moving (so the device would touch them at the rest was used. Dictator s game After the end of, a one shot Dictator s game was layed. Particiants were given a big folder containing a sheet with instructions and two enveloes: one was emty. 32 The instructions informed the articiant that he or she was to be Player A in a game. Particiants always had the role of Player A in the game but they were informed that the role was assigned by a random draw. Having the role of Player A meant that the articiant had the chance to either kee the whole amount of money in the enveloe or give some of it to Player B. The only information that articiants had about Player B was that he or she was also someone articiating in a research exeriment at the same institute and that his or her role had also been assessed randomly. The articiants were reassured that their resonse would be comletely anonymous as neither the exerimenters nor Player B would learn about their identity or about the amount that they had donated. After making their decision, articiants had to lace the money to be given in one of the enveloes and ut it in a box that was laced in the laboratory for this reason. They could kee the rest of the amount in the second enveloe and take it with them. Particiants did not know anything about the existence of this art at the beginning of the exeriment and were only told about it at the moment that the Dictator s game would take lace. They were instructed to oen the folder and follow the instructions. The exerimenter left the room during this art so the articiant would be alone. Questionnaire comletion Particiants received an with a link that led them to several online questionnaires, created hour and articiants could save their resonses at

9 EXPLORING MIRROR SENSORY SYNESTHESIA any time and resume later. For Dutch articiants, the Dutch version of each questionnaire was used while English versions were used for everyone exerience, history of neurosychiatric disorders, emathic behaviour, theory of mind, ersonality characteristics, sensitivity to other eole s states, ain ercetion and stress coing. The questionnaires were comleted in the same order as the one resented below. Personal information - Synesthesia. of sychiatric, neurological, or endocrine disease and current use of sychoactive drugs or corticosteroids were comleted. Particiants were also asked about their synesthetic exerience (van Leeuwen et al., synesthesia, the age of onset and the strength of synesthetic exerience over the course of time were comleted. Emathy assessment. In order to assess higher scores indicate enhanced emathy. For the PD subscale higher scores are translated to selforiented emotional reactivity. Theory of mind. The Reading the Mind in theory of mind test where the articiants ability to ut themselves into the mental state of others can be examined. Particiants were resented with of different actors of both sexes, and were asked to choose one out of four words that was best describing what the individual in the hotograh was thinking or feeling. Higher scores demonstrate enhanced theory of mind. Personality characteristics. The Big Five items and is designed to measure the comonents of the Big Five ersonality traits which are Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Oenness. Individuals have to indicate the extent to which each one of the ersonality traits mentioned describe their own characteristics using ratings from questions and it is designed to measure emathy in Sensitivity to other eole s state. The three main subscales: for cognitive emathy, for emotional reactivity and social skills. Each statement has to be rated on the scale of: strongly disagree, slightly disagree, slightly agree, strongly agree. emathetic behaviour ossible and the maximum behaviour ossible. cognitive and affective asects of emathy: Emathic feelings of symathy and comassion for others in distress, the PD self-oriented feelings of anxiety and distress in resonse to tense interersonal situations, the emotion and affective behaviour of others. The emotions of hainess, sadness, anger, love and fear can be determined. Particiants are asked to rate each one of the statements on how well it alies Pain ercetion. The Situational Pain to evaluate how articiants estimate their own sensitivity to ain. The extent to which a erson is able to differentiate ainful scenarios from neutral measures the tendency to adot the sychological oint of view of others. Each item is rated on Deressive behaviour. Deressive behaviour was assessed with the Zung self-reort scale (Zung, affective, sychological and somatic symtoms that 33

10 Kallioi Iouma have been related with deression. Each question Subjective ratings. indicating more severe levels of deression. Results Exeriment 1 - Reaction to arousing ictures invited to comlete the laboratory tests, one control as the amount of data was too low for inclusion, this articiant was excluded from all analyses. Furthermore, heart rate and skin conductance data were lost for one control due to technical failure and uil dilation data were lost for one synesthete due to a technical failure. excluded as they did not make correct use of the rating scales. Two synesthetes were excluded as they reorted having autistic traits. In a reeated measures ANOVA with the interaction between Condition x Grou was found for both valence F <.001 and (in (F an effect of grou for each stimulus condition (all <. negative condition. The results are lotted in Figure the context of negative and ositive ictures rating Fig. 3. Fig

11 EXPLORING MIRROR SENSORY SYNESTHESIA them as more unleasant and leasant resectively, than control articiants did. According with our hyothesis, synesthetes also rated unleasant ictures as more arousing and neutral ones equally arousing as control articiants. We had not redicted that synesthetes would rate ositive ictures as more leasant than controls. Additionally, we were execting that the ositive ictures would have been rated as more relaxing and calming by synesthetes comared to controls, which was not the case. Regarding the emotional faces conditions, a the ositive and neutral conditions. In a reeated found (F between Condition x Grou (F no Grou effect were found (F hoc aired samle t-tests in which the data from the different conditions were comared showed that the ositive and neutral condition uil dilation did not t Condition x Grou (F valence ratings. A one way ANOVA showed that the interaction was driven by the ositive emotional faces condition for valence F No effects were found for arousal. The results can These results show that synesthetes found the ositive emotional faces more leasant than negative emotional faces more negative, as we had hyothesised. We also did not observe any differences for arousal between synesthetes and controls as we were execting. Physiological resonses. Puil dilation. after cleaning were removed from analysis. In Figure dilation in the negative condition is larger than in from the negative condition (t and t Summarizing, we see the exected effect of the icture context with negative ictures inducing increased uil dilation comared to ositive and neutral ones, while there is no difference in uil dilation resonses between the grous. For the emotional faces conditions, the results were very similar. The results are lotted in Figure effect of Condition (F no interaction between Condition x Grou (F F Heart rate. synesthetes that had the required amount of artifactthe average heart rate across the icture resentation grou. A reeated measures ANOVA was run with Fig

12 Kallioi Iouma Fig. 6. Fig. 7. Fig. 8. Heart rate for arousing ictures of emotional controls. the factors Condition (negative, ositive, neutral F =.12. The results can be found at were found (Condition: F F F =.11. We can see in the lot as well that the interaction Synesthetes and controls seem to show a different attern across conditions with synesthetes heart rate going down moving from negative to neutral condition and the one of controls going u. For the emotional faces maniulation, the results were highly similar. A reeated measures ANOVA was run with the factors Condition (negative, ositive Skin conductance. The galvanic skin resonse data did not yield any usable results. After cleaning of the raw data there were skin conductance data N analyses. We did not consider this amount of Cortisol measurements. Cortisol results were control did not comlete the cortisol measurements and for another control the data from two measurements were missing. Baseline saliva cortisol levels, measured at the were found (Condition: F F and controls (t

13 EXPLORING MIRROR SENSORY SYNESTHESIA were execting that synesthetes mood would be more affected comared to the one of controls after the resentation of ictures with arousing context. In a searate reeated measures ANOVA with negative mood score before Exeriment 1 and during the baseline measurement, difference of ositive mood score before Exeriment 1 and Fig. 9. found (F and indicated that the synesthetes and controls the day that we erformed our exeriments in the laboratory. Thus any differences observed were only due to the exerimental handlings and the tests erformed. Exeriment 2 Diagnosis for Mirror sensory synesthesia Timeoint was observed (F that can be seen in Figure 9. No interaction between Timeoint and Grou was observed (F F The cortisol values after the exeriment are lower than before the exeriment for all articiants. This is unexected, because the arousing ictures should have increased and not decreased the cortisol levels according to our hyothesis. It seems that articiants were stressed in the beginning of the exeriment when coming to the laboratory and observe that the change in salivary cortisol levels over time did not differ between the synesthetes and the controls, which is contradictive to our exectations as well. The baseline measurement at home did not differ from the one in the lab across articiants and no baseline differences were observed between two grous, indicating that synesthetes as a grou do not have higher overall levels and that the measurements on the day of the exeriment at the laboratory were reresentative. Mood state. In a reeated measures ANOVA negative mood score before and after Exeriment 1, difference of ositive mood score before and after analyzed in this art. Data from one synesthete were lost and two synesthetes were excluded for not following the instructions correctly. We analyzed both the error rates and the reaction times across the different exerimental conditions. For the error rates, in a reeated measures Grou was found (F F F that the interaction in the error rates was driven by grou effects in the incongruent (t t conditions, while there were no differences in the error rates for the congruent condition (t can be seen that synesthetes make more errors than controls in both the incongruent and no_touch conditions. This is exected, since if the synesthetes were affected by their synesthesia, confusion would lead to more errors on the incongruent and no_touch conditions, but not on the congruent condition. For the reaction times, in a reeated measures between Mood x Grou was found (F 37

14 Kallioi Iouma Fig. 10. Fig. 11. controls. Condition x Grou (F there was a very clear effect of Condition (F (F Condition is mainly driven by longer reaction times in the no_touch condition, in which eole did not receive a touch to the face but did observe touch in Longer reaction times in the no_touch condition were exected as articiants waited until the end of the video waiting for any actual touch from the device. Synesthetes exerienced synesthetic touch in this condition which was confusing when having to reort what they felt as they had not exerienced actual touch from the device. Synesthetes overall delay that was observed in every condition could be due to an overall high level of confusion for synesthetes during this exeriment. Dictator s game The results from the Dictator s game were controls. Three controls and one synesthete were excluded, as they did not comrehend the instructions. We considered articiants who delivered the enveloe with the money for donation to ourselves and not to the box as instructed - while being alone in the room - as not having comrehended the instructions. In this way the An indeendent samles t-test revealed a between synesthetes and controls (t Fig. 12. The results are lotted in Figure 12. Age was r articiants giving larger amounts. Summarizing, as altruism in synesthetes. Questionnaire comletion The battery of online questionnaires on emathy and ersonal characteristics was comleted by 11 synesthetes and seven controls who articiated in the laboratory tests. Furthermore, synesthetes comleted an exit questionnaire in the laboratory in which they reorted on their exerienced synesthesia during the exeriments. Controls comleted the exit questionnaire without the questions about synesthetic exerience. First of all, the scores on the online questionnaires were comared between synesthetes and controls. Additionally, three sets of 38

15 EXPLORING MIRROR SENSORY SYNESTHESIA (M c ) for each comleted questionnaire. We failed to rating that were comleted during the laboratory tests, the rest of the correlations with all the online questionnaires should be regarded as exloratory. there were correlations between the synesthetes synesthetic touch during Exeriment 2 and their exerience of synesthetic touch and ain during Exeriment 1 in the exit questionnaire. The second set of correlation analyses comared the ratings of exeriencing synesthetic touch in Exeriment 2 and the ratings of exerience of synesthetic touch and ain during Exeriment 1 with the scores on the ictures of Exeriment 1 with the scores on the online questionnaires and this time all articiants were included. For the sake of brevity only the Correlations between strength of synesthesia and valence/arousal ratings in Ex. 1 Particiants who indicated to exerience stronger synesthetic ain during Exeriment 1 rated unleasant images as more unleasant (r r arousing (r reorted exeriencing stronger synesthetic touch exciting (r who indicated to exerience stronger synesthesia for touch in Exeriment 2 were less likely to reort ositive faces as unleasant (marginal effect, r faces as exciting (marginal effect, r = the had hyothesised that the stronger the synesthetic exerience, the more affected by arousing ictures synesthetes would be. Grou Comarisons on Questionnaires We conducted a series of one-way ANOVAs where we comared the Mean scores of the synesthetes (M s Mind in the Eyes exeriment, the Situational Pain scale. The analyses did reveal that synesthetes scored higher on the Emathetic Concern art of M s M c F = IRI score (IRI Total M s M c F higher on extraversion (M s M c F M s M c F scored higher on almost all Emotional Contagion sadness scale. We found the following statistics for the ECS scales: Hainess M s M c F M s = 12.9, M c F M S = 12.1, M c F M s M c F M s M c F our hyothesis synesthetes scored higher on ECS scales, at some arts of the IRI and the BFI scales for extraversion and oenness (in agreement with what is already shown for synesthetes of other tyes Reading the Mind in the Eyes and in other subscales of the IRI, which was not the case. Correlations between strength of synesthesia and online questionnaire scores Particiants who reorted exeriencing stronger synesthetic ain during Exeriment 1 scored higher on the total IRI scale (r articiants exeriencing stronger synesthetic touch subscale (r deression scale (r of exerienced synesthetic touch during Exeriment 2 did not reveal any correlations with any of the questionnaires scores. The observed correlations are exected as the stronger the synesthesia, the more emathic and sensitive to their environment we consider that synesthetes will be. We did not emathy measures as hyothesised. 39

16 Kallioi Iouma Correlations between valence/ arousal ratings in Ex. 1 and online questionnaire scores In these correlations, controls are included as well. Particiants who rated unleasant images as more unleasant scored higher on the total IRI scale (r r (r unleasant images as more arousing also scored higher on the IRI fantasy subscale (r r hainess: Love: (r r r Sadness: (r r Particiants who rated ositive emotional faces as more leasant also scored higher on the total IRI scale (r scale (r excet hainess and sadness. ECS Love: (r r ECS anger: r r as more exciting also scored higher on the emotional articiants who rated negative faces as more arousing also scored higher on the fantasy subscale of the IRI (r subscale of the BFI (r three subscales of the ECS: Love: (r = r r It is exected that more emathic articiants, as indicated from the IRI measure, would have more extreme ratings. It is also not surrising for individuals who are more sensitive to their environment, as indicated from the ECS measure, to have more extreme ratings as well. However we would also exect that more extreme ratings would in the Eyes test scores, which was not the case. Discussion In this study we characterised mirror sensory synesthetes with regard to their emathic and altruistic behaviour, theory of mind, ersonality characteristics and ain ercetion. We also examined whether exeriencing this tye of synesthesia is accomanied by hysical resonses of the body. In the case differential bodily resonses would be observed for synesthetes, our question was whether any enhanced emathic or altruistic behaviour would accomany these effects. We successfully diagnosed mirror-touch synesthesia with an established behavioural rate ictures with leasant, unleasant and neutral context more extreme than controls. These ratings were correlated with the strength of the synesthetic demonstrating an effect of synesthesia in how much synesthetes are affected by other eole s state. We levels for synesthetes during the viewing of arousing ictures. The Dictator s game revealed enhanced altruistic behaviour but a number of questionnaires about emathy, and the theory of mind test did not seem to have no alterations in their ain ercetion and demonstrate ersonality characteristics similar to the ones of synesthetes of other tyes. successful. Synesthetes got confused by the set u that included actual touch as well as synesthetic touch, making more errors than controls in exactly those conditions where their synesthesia was interfering, namely in the incongruent and no_touch conditions. Synesthetes were slower than controls for all stimulus conditions, but we did not observe synesthetes and controls for the different categories as it is reorted in the literature (Banissy & Ward, articiants were not ressured enough to answer very quickly. Thus, synesthetes may have taken more time overall as they found the exeriment the factor of seed been emhasised more, they might have been faster in the congruent condition after all. For a number of synesthetes it was not very hard to distinguish between the synesthetic touch and the actual touch from the device, as the way they exerienced these two forms of touch was very different. Thus, our aradigm did not work otimally for very sensitive synesthetes. In Baronan aim has been made. Further analyses of our data from the ale condition from Exeriment 2 might 40

17 EXPLORING MIRROR SENSORY SYNESTHESIA From the icture ratings in Exeriment 1 we saw that synesthetes were more affected by arousing ictures than controls. After observing a icture with leasant or unleasant context synesthetes were both as an increased sensitivity to other eole s state and enhanced emathic behaviour. The fact that ictures ratings were correlated with the scores We can also see that the strength of the was highly correlated with the extent to which articiants indicated to be affected by arousing ictures. Particiants who indicated exeriencing stronger synesthetic ain rated unleasant images as more unleasant, leasant images as more leasant and unleasant images as more arousing. Also, synesthetes who reorted exeriencing stronger synesthetic touch rated leasant images as more exciting. The synesthesia is thus very imortant for the ratings that were given and the way the articiants exerienced the ictures. Turning to the hysiological resonses that were recorded during the ictures exeriment, it is interesting to observe that for the uil dilation, our maniulation worked, in the sense that there were different resonses for each one of the stimulus categories in the exected direction. The articiants uils were more dilated in the negative condition than in the ositive and neutral conditions, indicating a resonse for the negative condition. We did not see an effect of grou though, similar to the lack of a grou effect in the other hysiological measurements. It is a ossibility that there is no hysical resonse that accomanies the synesthetic exerience. However, there are several reasons why our maniulation may not have been strong enough. It could be the case that our ictures were not negative or ositive enough to elicit hysical resonses and that we would have observed an effect if we would have used ictures with more extreme arousing context. This lack of affect can also be seen in the PANAS scores where synesthetes did not state a different emotional affect than control articiants overall. Moreover as all ictures had a rather comlicated background it can be that other asects of the icture than the asects that we wanted to emhasize have drawn the attention of ratings would not necessarily only corresond to the synesthetic sensations elicited on articiants bodies. An answer to this question could be found by analyzing eye-movements and the location of larger samle size and more extreme ictures might have imroved the set-u and yielded a grou effect. We intend to erform further analyses searately for the hysiological resonses of the most extreme ictures from each condition as this might still reveal differential body resonses in synesthetes and controls. As we had hyothesised, the Dictator s game revealed enhanced altruistic behaviour for synesthetes. We observed a large effect with the altruistic trait is been studied in mirror sensory synesthesia. A ossible exlanation is that because of being more suscetible to other eole s state, misfortunes around them as they are also directly affected themselves. An alternative interretation involves the differential self-other distinction and reresentation of self-identity that has been found in mirror sensory synesthetes (Maister, Banissy & enhanced emathic and altruistic behaviour (Cialdini is demonstrated in in-grou (enhanced self-other mirror sensory synesthetes may be the outcome of a blurred self-other image. Several concerns should be ket in mind when interreting the results of the Dictator s game. Some synesthetes and controls donated more than the exected amount of money, which was actual extreme altruistic act or as a denial to lay the game. A ossible cause for the last exlanation could be that articiants were feeling insulted from this unexected offer of money. Performing the analyses excluding the articiants who donated grou difference (t the grou effect is robust. The effect of age that we found could either be exlained by the fact that older articiants had a smaller need of money or because of altruistic behavior has been enhanced game indeed measured the trait of altruism and that our set u was convincing for the articiants. We cannot exclude the ossibility that other feelings articiants resonse would indeed be anonymous contributed to their decision about the distribution 41

18 Kallioi Iouma of money. Moreover it could be the case that our way of recruiting synesthetes layed a role, as it was more ersonal than the one for controls. Before their visit to our laboratory synesthetes were extensively interviewed via s. Synesthetes scored higher on the Emathetic Concern art of the IRI, on the total IRI score, which can be interreted as an indication for enhanced emathic behaviour. Interestingly, synesthetes scored higher on almost all Emotional Contagion scales with the only excetion being the sadness scale, showing that they are indeed affected more by their environment and the different emotions around them. However, synesthetes did not score in a different way than controls in any other of the emathy measures or in the reading the mind in the eyes test which is in agreement with Baron-Cohen et Acknowledgements Hubert Voogd for their recious hel on constructing the tactile device and arranging the technical set-u. We are also grateful to the synesthesia associations and researchers who heled with recruitment and to all of our articiants for their time and motivation. References of auditory-visual synesthesia reveals evidence of American Journal of Human Genetics, 84 are needed for a concrete conclusion on emathic behaviour in mirror sensory synesthesia. Larger samles and use of alternative measures of emathy might be crucial in shedding more light on the toic. The results of the BigFive ersonality questionnaire revealed enhanced extraversion and oenness to new exerience in mirror sensory synesthetes which are traits that have been observed in the ast for synesthetes with other interesting observation is that exeriencing mirror sensory synesthesia seems not to alter individuals overall ercetion of ain, as it was measured in the were not comleted from all the articiants that were tested in our laboratory we cannot exclude the ossibility of a tye 1 error due to our small samle size. Conclusion not identity recognition, in mirror-touch synesthesia. Society for Neuroscience, 31 E., Walsh, V., eole with synaesthesia: Do synaesthetes have an Personality and Individual Differences, 54 is linked with emathy. Nature Neuroscience, 10 Familial atterns and the origins of individual differences in synaesthesia. Cognition, 106 Baron-Cohen, S., Robson, E., Lai, M.-C., & Allison, C. with Heightened Emathy, and Can Occur with Autism. PloS One, 11 Is synaesthesia more common in autism? Molecular Autism, 4 that mirror sensory synesthesia is accomanied by enhanced altruistic behaviour. Mirror sensory synesthetes indicated to be more strongly imacted by ositive and negative images than control articiants. Their synesthetic exerience does not alter their ain ercetion but results in them develoing ersonality characteristics that synesthetes of other tyes show. Further studies and additional analyses are needed in order to make solid conclusions about emathic behaviour and body resonses in mirror sensory synesthesia. Syndrome or High Functioning Autism, and Normal Sex Differences. Journal of Autism and Develomental Disorders, 34 Adults, and Adults with Aserger Syndrome or Highfunctioning Autism. Journal of Child Psychology and Psychiatry, 42 American Economic Review, 96 42

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