liveness through the lens of agency and causality
TRANSCRIPT
Liveness Through the Lens of Agency and Causality
Florent BerthautUniversity of [email protected]
David CoyleUniversity College Dublin
James MooreGoldsmiths, University of
Hannah LimerickUniversity of Bristol
ABSTRACTLiveness is a well-known problem with Digital Musical In-struments (DMIs). When used in performances, DMIs pro-vide less visual information than acoustic instruments, pre-venting the audience from understanding how the musiciansinfluence the music. In this paper, we look at this issuethrough the lens of causality. More specifically, we inves-tigate the attribution of causality by an external observerto a performer, relying on the theory of apparent mentalcausation. We suggest that the perceived causality betweena performer’s gestures and the musical result is central toliveness. We present a framework for assessing attributedcausality and agency to a performer, based on a psycholog-ical theory which suggests three criteria for inferred causal-ity. These criteria then provide the basis of an experimentalstudy investigating the effect of visual augmentations on au-dience’s inferred causality. The results provide insights onhow the visual component of performances with DMIs im-pacts the audience’s causal inferences about the performer.In particular we show that visual augmentations help high-light the influence of the musician when parts of the musicare automated, and help clarify complex mappings betweengestures and sounds. Finally we discuss the potential widerimplications for assessing liveness in the design of new mu-sical interfaces.
Author KeywordsDigital Musical Instrument, Liveness, Agency, Augmenta-tions, Apparent mental causation
ACM ClassificationJ.5 [Computer Applications] ARTS AND HUMANITIES—Performing arts (e.g., dance, music) H.5.5 [InformationInterfaces and Presentation] Sound and Music ComputingJ.4 [Computer Applications] SOCIAL AND BEHAVIORALSCIENCES — Psychology
1. INTRODUCTIONPerformers using Digital Musical Instruments (DMIs) pro-vide the audience with a considerably different experience toacoustic instruments and this is largely due to the complex-ity and diversity of DMIs. A key difference between the two
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lies in the visual information provided to the audience dur-ing a performance. The visual component of a performanceusing an acoustic instrument is rich with information, forexample they can convey emotion to the audience and af-fect the audience’s emotional state [4] [13]. DMIs lack sucha rich visual information transfer to the audience, largelydue to the absence of a direct physical link between the ges-tures and the sound. DMIs tend to produce more complexsounds than acoustic instruments this increased complexitymakes it more difficult to understand how the instrumentsare used.
This paper investigates liveness from the perspective ofthe audience’s perceived causality between the performer’saction and the music they hear. We draw upon the theoryof ’apparent mental causation’ [14] which was formulatedto account for the attribution of causality of one’s own con-scious thoughts and their actions. This is known as theexperience of self-agency - the experience of initiating andcontrolling one’s actions to influence the external environ-ment - but can also be extrapolated and applied to the expe-rience of attributing agency to another agent. We focus onan examination of whether this theory can be used as a validframework for identifying causality between a performer us-ing a DMI, their actions, and the observers’ perception ofthe performance. We believe that this inference of causalitybetween the performer and their actions is central to the au-dience’s perceptions of liveness during a performance. Ourcontribution is two-fold. Firstly, we introduce a psycholog-ical framework based on inferred causality for the analy-sis. Secondly, through the empirical application of visualaugmentations in line with this framework we gain insightsinto audience’s perception of causality in performers’ use ofDMIs.
In Section 2, we describe how related work has shownthat causality is an important part of liveness, and thatvisual augmentations can be used to reveal information tothe audience. Section 3 explains the psychological researchfrom which we derive our framework. The framework is pre-sented in detail, illustrating how DMIs lack enough visualinformation for inferred causality. Later, Section 4 describesthe visual augmentations designed to provide this missinginformation. Additionally, the experimental protocol is out-lined. Finally we discuss our findings and the opportunitiesopened by our approach for the NIME community.
2. RELATED WORKTo our knowledge, no previous research has focused on thestudy of inferred causality in the context of the liveness issuewith DMIs. However, some research have speculated aboutits importance in the perception of liveness.
In [12], the authors discuss the importance of causalityin the perception of liveness. However, they investigate the
evaluation of liveness through the measurement of specta-tor’s emotions, in particular enjoyment. Nonetheless, intheir observations from participants answers, several dimen-sions that have an effect on liveness perception are stronglylinked to the perception of causality, such as visibility ofgestures, miming effect, interaction fidelity and conventionson instrumental control.
A mixed-reality system providing visual representationof the mechanisms of DMIs aimed at improving livenesswas introduced in [1]. The Rouages system displays theconnections between gestures and the sound processes withvisual links, so that spectators can see the gestures andcorresponding sound process of the instrument. This is anexample of visual augmentation aimed at mapping the per-formers’ actions to the resultant sound, however was not de-veloped within a theoretic framework of causality. Becauseof this, the nature of the gestures, such as continuous or dis-crete are not visualised, which can lead to confusion whena similar gesture leads to changes of different type in thesound. Also, the system does not represent which partic-ular parameter of a sound process individual gestures con-trol, which would enable it to be distinguished from thosecontrolled through an automated process. Furthermore, itdoes not account for temporal disruption of musicians’ ac-tions, e.g. delay or quantization. Instead it only representscontrols immediately applied to the sound.
Intentions and prior knowledge regarding DMIs was in-vestigated in [7]. They show that explaining the instrumentto the participant with preliminary videos had a positiveimpact on their enjoyment of the performance. The betterparticipants understood the instrument and the way it wasplayed, the better they were able to appreciate the perfor-mance. The authors suggest that, because it is not alwayspossible to explain an instrument beforehand, interactiondesign should make the instrument and it’s interaction moreobvious. [9] echoes that familiarity with DMIs positivelyimpacts the audience’s experience of a performance. Famil-iarity and understanding are driven by an awareness of howmusicians use DMIs to produce sounds. The audience havea greater experience of liveness when there is a greater ex-posure to the causality between actions and their musicaloutcomes. As pointed out in [3], ”... the onus of justifi-cation of liveness is shifted to the causal link between theperformer’s action and the computer’s response”. Acous-tic instruments are based on the physical properties of el-ements composing the instruments and on the mechanicalenergy transfer between the musicians’ movements and thevibrations produced. For example, when observing a drum-mer hitting a cymbal, the causality between the gestureand sound can easily be inferred because one has seen thearm movement, the collision with the cymbal and heard thesound. These are causal events that humans observe andexperience themselves on a daily basis. However, DMIs in-volve causal events which are far less familiar. This maybe due to the lack of visual information provided to the au-dience about the parameters of sounds and how they areinfluenced by the performer during the live performance.This lack of visual information also provides the audiencewith less familiarity with the instrument in order to infercausality between gestures and sound. Therefore, a disen-gagement occurs between the performer, their actions, themusic and the audience.
In this paper, we look at the liveness issue focusing onthe perceived causality between gestures and the resultantsound. In particular, we propose a theoretical frameworkto analyse how this perception of causality is impaired inDMIs. We also describe visual augmentations that specifi-cally aim at visualizing the causality between gestures and
musical results in DMIs.
3. INFERRED CAUSALITY3.1 Attribution of Agency”When a thought appears in consciousness just before anaction (priority), is consistent with the action (consistency)and is not accompanied by conspicuous alternative causesof the action (exclusivity), we experience conscious will andascribe authorship to ourselves for the action[15]”
The quote above summarises the theory of apparent men-tal causation. According to the current thinking in psy-chology, inferences regarding the causal link between a con-scious thought and action are central to the attribution ofself-agency. Crucially, if the inference about the causalitybetween a conscious thought and an action meets three cri-teria - priority, consistency and exclusivity - the cause ofthe action will be ascribed to the self. This theory has beenshown experimentally, for example, priming people withthoughts corresponding to these three criteria regarding anaction that they did not perform, induced a false sense ofself-agency for the actions [14]. It is widely thought thatthe mechanisms supporting the attribution of agency to theself also support the attribution of agency to others [6] [5].A common system for attributing intentions to the self andothers ”enables us to communicate mental states and therebyshare our experiences” [6]. Here, we extrapolate the criteriaof self-agency attribution and apply them to investigate theaudience’s attribution of agency to a performer.
3.2 Liveness, DMIs and criteria for inferredcausality
Related work suggests that issues with visual informationperformance with DMIs adversely affect the perception ofliveness. More specifically, a lack of visual information mayimpair the audience’s ability to make inferences about theperformer’s intentions, actions and musical outcomes, andthus degrade their experience. For instance, contrary toacoustic instruments, the interfaces used in DMIs do notprovide any visual information on the nature of the soundsthe instrument generates. The same physical interface canbe used to control any parameter of any sound process. Thegestures can also be subtle or hidden, and therefore not per-ceived fully by the audience, but at the same time have astrong impact on the musical result. Finally, with changesin scale and nature between the input and output values,the transfer of energy is very different to that which is vi-sually perceived for acoustic instruments. We hypothesisethat the impaired visual information with DMIs may causedisruption in one or more of the 3 criteria for causal infer-ence and thus result in a diminished attribution of agencyto the performer.
3.2.1 PriorityIn Wegner & Wheatley’s original theory of apparent men-tal causation [14], priority refers to the temporal order ofevents. If a conscious thought occurs before the action, andwithin a sufficiently close time window, priority criterion ismet, which in turn supports an inference of agency. Wesuggest that this criterion can be adapted and applied toinvestigate audience’s attribution of agency to a performer.This can be done by focusing on the temporal nature of theperformer’s actions in relation to the musical outcome.
An example of how priority can be impaired in DMI’s isthe use of quantization, quite common in instruments whichrely strongly on a pulse such as those based on pre-existingor live-recorded loops. In order to keep all loops temporallyaligned, it is easier to delay their activation or manipulation
until the next beat or bar. Thus, although the outcome isoccurring after the action, it may be such a long time afterthe action that the audience cannot infer causality.
3.2.2 ConsistencyConsistency [14] refers to the congruence between the con-tent of intention and the related action. That is, if theaction is consistent with the prior thought, an inference ofself-agency is supported. Here we adapt this criteria forthe purpose of investigating attribution of agency to a per-former by considering the consistency between actions andthe musical outcome.
Musical performances involving DMIs disrupt this cri-teria, through discrepancies between the nature and scaleof the gestures and those of the expected resulting soundevents. For example, instantaneous and continuous excita-tion gestures, as proposed by Cadoz [2], can be easily un-derstood in acoustic instruments, because the musical resultfollows the nature of the gesture. This principle rarely holdsin the case of DMIs. For example, an instantaneous press ona button can trigger a ramp on the pitch of a sinewave. Onthe other hand, continuous gestures can be used to triggerdiscrete changes in the sound, such as jumps between mean-ingful values of a parameter. Differences can also appearbetween the scale of gestures and the scale of the resultingmusical event. For example sometimes turning a knob willresult in a subtle change in the timbre of one sound process,equally, the same gesture can apply a strong change suchas a low-pass filter on the whole musical output of the in-strument. This issue relates to the difference between inputand output complexity of DMIs, as described in [11].
3.2.3 ExclusivityExclusivity [14] refers to the number of possible causes foran action. Attributions of self-agency are supported in sit-uations where one’s intention is the most likely cause ofthe action. This can be applied to attribution of agency toanother in a performance context in several ways. In mul-tiprocess DMIs, several sound processes generate the soundat the same time, some directly from a musician’s gestures,other in a completely automated manner. This results inmusical events for which the origin is not clear. Exclusiv-ity issues also arise in laptop orchestras, where it can bedifficult for the audience to perceive which performer is re-sponsible for the changes in the resulting music. DMIs canalso make use of complex mappings. As described in [10],one gesture can be connected to multiple sound parameters,or multiple gestures can be combined to modify a single pa-rameter. Multiple changes in the sound occur while multiplegestures are being made without a clear connection betweena gesture and its effect.
4. EXPERIMENTSo far we have discussed the theory of apparent mental cau-sation which defines three criteria for attribution of agencyto themselves. We have explained how this theory couldbe extrapolated and applied to the attribution of agencyto others. Here we are focusing on the audience’s attribu-tion of agency to a performer. The related work on livenesshighlights perceived causality as an important feature inliveness. Furthermore this theory could be used to test live-ness in performance with DMIs. This section presents anempirical study where we applied the adapted frameworkfor apparent mental causation to investigate the effect ofvisual augmentations on liveness in a performance using aDMI.
Participants were presented with a set of videos whichshowed a live performance using DMIs. This study intends
to investigate whether visual augmentations have an impacton attributed agency. For each of the three criteria for in-ferred agency, a different DMI was designed. Participantswould watch a video of each DMI being performed with twovisual conditions - with visual augmentations (WithAug)and without visual augmentations (NoAug) (see Figure 1).Participants were asked to make ratings regarding the in-fluence they believed the performer had over the music theyheard (agency ratings). Participants were also asked to ratetheir confidence for their judgements (confidence rating).We hypothesise that for all the criteria, visual augmenta-tions will provide the missing link between required to makecausal inference regarding the performer’s gestures and thusattribute agency. Therefore, the presence of WithAug willresult in participants providing higher ratings about agencyof the performer, compared to NoAug. In addition that theconfidence ratings will be higher in the WithAug conditionsthan in the NoAug condition for all criteria. DMIs involvecausal processes that are unfamiliar to a typical audience.By providing the audience with visual augmentations high-lighting the musical parameters and how they influence themusic, they will become more familiar with the causal pro-cesses and thus have higher confidence ratings as discussedabove in Section 2.
Figure 1: Stills of experiment videos. A) Exclusiv-ity Without Augmentations. B) Exclusivity withAugmentations. C) Priority with Augmentations.D) Consistency with Augmentations.
4.1 Methods and Apparatus4.1.1 Visual Augmentations
To create the visual augmentations, we first represent soundprocesses as 3D shapes placed below the DMI, as depictedon Figure 1. We use a set of audiovisual mappings followingstudies such as [8]. These are: 1) color hue and luminanceassociated to pitch, 2) shape associated to timbre/soundidentity, 3) size associated to loudness, 4) rotation on the Yaxis associated to pattern. These mappings make it possibleto visually discriminate between the parameters that are be-ing controlled on each sound process and between the soundprocesses themselves. More importantly, the connectionsbetween the gestures and sound processes are representedwith specific 3D widgets. One of these widgets is added toeach shape representing a sound process, as shown on Figure1. The widgets are composed of three parts, representingthe input, the core and the output of mappings. An inputsegment is created for each sensor attached to the soundprocess. It appears when a gesture is sensed and represents
the controlled parameter at the sensor value. All the in-put segments are connected to a core segment that appearswhen one of them is activated. While the input segmentsdisappear once the gesture is over, this core segment re-mains visible until the change is applied to the sound. Thecore segment displays the values of the parameters as theywill be set on the sound processes, making changes in scalefrom the sensor values obvious. The output segment of thewidgets goes from the core to the sound process, displaythe output value and appears only when the value is ap-plied to the parameter of the sound process. Overall, these3D widgets will therefore compensate for the disruption ofthe three causality criteria by displaying the connectionsand parameters between gestures and sound parameters.
4.1.2 DMIs and VideosFor the purpose of the experiment, we designed three DMIs,all with the same interface and sound processes, but whichdiffer in the chosen mappings, so that each of them highlighta disruption of one of the criteria for inferred causality andattribution of agency. We filmed short performances witheach DMI from two camera angles front and above, as shownon Figure 1. Two camera angles were chosen here to capturethe reality of viewing a musical performance from differentviewing perspectives. Therefore there were 3 x 2 x 2 videosin total; criteria x camera angle x augmentation condition.
The QuNeo controller was used as the interface for theDMI because it requires generic gestures, such as instanta-neous (hits) and continuous (presses and 1D displacements).On the QuNeo, 16 pressure pads and four touch faders wereused. The three DMIs also rely on the same four sound pro-cesses, designed to be perceptively separable: One low andone high pitched continuous harmonic sounds composed ofsinusoids (respectively between 70Hz and 170Hz, and be-tween 260Hz and 530Hz), with controllable pitch and vol-ume; On low and one high pitched percussive sounds (whitenoise mixed with sinusoids respectively at 80Hz and 260Hz)with controllable velocity. In addition, four different pat-terns were composed for each sound process, at a tempo of120bpm.
For the instrument designed to illustrate the priority cri-teria for inferred causality, our goal was to make it difficultfor spectators to determine temporally when a change inthe musical pattern has been triggered by the performer’sactions. Therefore, the changes in the musical pattern forthe sound processes were applied every 8 beats. The secondinstrument was designed to disrupt the consistency crite-ria for inferred agency, i.e. the spectator’s expectations ofconsistency between action and outcome. We assume thatthe participants expect discrete gestures, such as striking apad, to trigger a discrete change, and the same for contin-uous gestures. Therefore the DMI was designed to matchdiscrete gestures with continuous changes in the music andcontinuous gestures with discrete changes in the music. Thethird DMI was designed to disrupt the exclusivity criteriaby introducing ambiguity over the originating source of themusic - either from the live hand gestures of the performeror pre-programmed, automated processes mediated by thecomputer. This was achieved by the same musical param-eters being controlled by both live gestures and automatedprocesses throughout the video. Automated patterns onpitch and volume of the harmonic sounds and the velocityof the percussive sounds were interrupted by the performerusing the interface. The presence of the laptop in the videowas intended to create the ambiguity between live controland automated processes.
4.1.3 ProtocolThe experiment is a repeated measures design where all par-ticipants viewed all 12 videos. To control for potential ordereffect, we counterbalanced the order that videos and crite-ria were viewed. 17 participants, aged between 18 and 40years completed the experiment and in return they receiveda £10 gift voucher.
Participants were asked to sit in front of a 2x1m screenprojected onto a white wall. The lighting was kept constantfor all participants. We chose a large projection to bestre-create a live music performance. A speaker (BehringerMPA40BT-Pro) was used to playback the sound from theperformance, again to re-create a live performance.
At the end of each video, two rating boxes appeared onthe screen, asking the following questions: 1) How much wasthe music influenced by the performer’s hand gestures ? 2)How confident are you about your judgement ? Participantsthen made their ratings for both questions on a scale from1 to 10. For the agency rating, 1 on this scale representedthe lowest rating corresponding to the judgement that theperformer had no influence over the music. A rating of 10on this scale corresponded to the judgement that the musicwas influenced only by the performer. These ratings wereexplained to the participant before the study.
4.2 Results4.2.1 Consistency
A repeated measures 2x2 ANOVA was performed for Cam-era position X Augmentation condition for both agency rat-ings and confidence score. There was a significant maineffect for the confidence ratings in the augmentation con-dition F(1,16) = 4.480, p = .05. A follow up t-test for allthe NoAug and WithAug irrespective of camera condition(because camera has no effect on the confidence ratings).WithAug condition has significantly higher confidence rat-ings than NoAug t(33) = -2.54, p = 0.016. Therefore thepresence of visual augmentations resulted in a significantlyhigher confidence rating.
4.2.2 ExclusivityA repeated measures 2x2 ANOVA was performed for Cam-era position X Augmentation condition for both agency rat-ings and confidence score. There was a significant maineffect for the agency ratings in the augmentation condi-tion F(1,16) = 7.391, p = .015. To further examine themain effect, we performed a follow up t-test for all NoAugand WithAug conditions irrespective of camera position.t-tests revealed that there was a significant difference be-tween agency ratings NoAug and WithAug; t(33) = -3.19,p= 0.003. Therefore participants rated agency significantlyhigher in the WithAug condition than NoAug.
4.2.3 PriorityA repeated measures 2x2 ANOVA was performed for Cam-era position X Augmentation condition for both agency rat-ings and confidence scores however no main effects werefound.
4.3 DiscussionThe results show that the participants’ perception of theperformances in our study were significantly altered usingvisual augmentations in two of the three criteria examined.Participants’ perception of the videos of a live performanceusing the DMI designed to disrupt consistency showed asignificant improvement of confidence for their agency rat-ings with the visual augmentations. The videos in the con-sistency condition were designed to make the gestures in-consistent with participants’ expectations regarding actions
and their influence over the music. This result suggeststhat the addition of visual augmentations to represent thecausal link between the performer’s gestures and the soundsproduced, increased participants’ confidence in their judge-ments. This finding in the confidence rating is in line withour hypothesis. Our hypothesis was based on the prior re-search suggesting that familiarity with the causal processesinvolved in producing music has a positive effect on au-diences’ experience of liveness [3]. This may explain whythe agency ratings were not altered by the augmentationcondition because in reality the influence of the performerover the music was constant for all four videos. We sug-gest that providing visual information in a context wherethe outcome of gestures during a performance are inconsis-tent with standard expectations gives the audience a betterunderstanding of such processes.
The results regarding the exclusivity condition showed asignificant improvement to the agency ratings with the vi-sual augmentations. This was in line with our hypothesisand suggests that when there are multiple potential causesfor the music, the addition of visual information regard-ing the origin of gestures and their causal influence overthe music improves attribution of agency to the performer.Further, that when the amount of influence the musicianhas over the music is relatively low, visual augmentationassists the audience to distinguish which parts of the musicthe performer is actually controlling.
There was no difference between the NoAug and WithAugconditions for both confidence ratings and agency ratings inthe videos designed for the priority criteria. This may bedue to an incorrect interpretation of the priority criteria,temporal order of events being more central than temporaldelay. Temporality is a complex issue in the context of mu-sic and a more systematic investigation of this is required.
5. CONCLUSIONIn this paper, we used a well-established theory for appar-ent mental causation and agency to design the visual in-formation provided to the audience which conveyed specificparts of causality between the performer and their actions.By isolating three distinct criteria of inferred causality andthen asking participants to rate both their judgements ofagency and confidence about these judgements, we are ableto better understand the nature and application of visual in-formation during a performance. This framework can helpinform the design of new musical interfaces so that they cancompensate for known issues in performances In particularwe have shown that restoring the perception of causalityhelps highlighting the influence of the musician in a perfor-mance where part of the musical result is automated. Wehave also shown that causality helps the audience under-stand the link between musicians’ gestures and the resultingchanges in the music.
We see two main directions for future research. Firstly,a further investigation into the results presented in this pa-per and establish thresholds for the point at which the au-dience’s perception changes. For example, further inves-tigating how inconsistent the action and outcome has tobe before the audience become less confident about theirjudgements of agency. Secondly while the framework wehave discussed is applied to attributed agency, the psycho-logical research that it relies on focuses on self-agency. Alogical follow-up will therefore be to look at the perceptionof causality by the musicians themselves while they are per-forming. This framework could then be used to assess boththe interaction with and perception of new musical inter-faces.
6. ACKNOWLEDGMENTSThis project was partially funded through the Marie CurieFP7 framework (Grant Agreement PIEF-GA-2012-330770).
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