Flow and Immersion in First-Person Shooters: Measuring the player���s gameplay experience Lennart Nacke Blekinge Institute of Technology Box 214 Karlshamn, Sweden +46-455-385938 Lennart.Nacke@bth.se Craig A. Lindley Blekinge Institute of Technology Box 214 Karlshamn, Sweden +46-455-385938 Craig.Lindley@bth.se ABSTRACT Researching experiential phenomena is a challenging undertaking, given the sheer variety of experiences that are described by gamers and missing a formal taxonomy: flow, immersion, boredom, excitement, challenge, and fun. These informal terms require scientific explanation, which amounts to providing measurable criteria for different experiential states. This paper reports the results of an experimental psychophysiological study investigating different traits of gameplay experience using subjective and objective measures. Participants played three Half- Life 2 game modifications while being measured with electroencephalography, electrocardiography, electromyography, galvanic skin response and eye tracking equipment. In addition, questionnaire responses were collected after each play session. A level designed for combat-oriented flow experience demonstrated measurable high-arousal positive affect emotions. The positive correlation between subjective and objective indicators of gameplay experience shows the great potential of the method presented here for providing real-time emotional profiles of gameplay that may be correlated with self-reported subjective descriptions. Categories and Subject Descriptors K.8.0 [Personal Computing]: General ��� Games. General Terms Measurement, Design, Theory. Keywords Game design, flow, immersion, gameplay experience, psychophysiology. 1. INTRODUCTION With the growing maturity of game science as a research field, more and more studies are devoted to the empirical investigation of different experiences in gaming. The primary concern is to gain a more thorough understanding of subjective experiences referred in terms such as immersion, presence and flow. Not only do these terms currently lack well-accepted common meanings, but also for game designers, clear and testable definitions of constructs such as immersion and flow would be invaluable, since these are considered to be the holy grail of digital game design. Our own studies focus upon First-Person Shooter (FPS) games, which aim to provide a holistic game experience for the player by removing player representations (like avatars) and putting the player in first- person perspective. In an FPS, the player can fully identify with the game character represented only by weapons and/or hands seen as virtual prostheses that reach into the game environment [14]. This means that in an FPS a player virtually turns into the game character as they feel like they are acting directly in the virtual game world. In addition to the FPS perspective, the consequence and meaning of player action within the environment and its impact on gameplay greatly influence the feeling of immersion [21]. The study of FPS games may simplify the investigation of these factors by removing issues of identification (or not) with a character viewed from a third-person perspective. 1.1 Immersion A qualitative study conducted by Brown and Cairns [3] analyzed players��� feelings towards their favorite game and led them to propose three gradual and successive levels of player immersion: engagement, engrossment, and total immersion. The latter level is used interchangeably with the concept of presence, a state facilitated by feelings of empathy and atmosphere, which links immersion to factors of graphics, plot and sounds in addition to emergent gameplay (since visual, auditory and mental elements are mentioned in this context). While it is plausible to see immersion as a gradual phenomenon that builds up over playing time, this study shows that the lack of a clear definition for presence and immersion causes the terms to be used interchangeably for phenomena that may not be the same. Ermi and M��yr�� [11] subdivided immersion into three distinct forms: sensory, challenge-based and imaginative immersion. ���Sensory immersion��� relates to the audiovisual execution of games. This dimension of immersion is easily recognizable as it can be intensified through intensifying its components, such as creating more compelling graphics or playing on a much larger screen or with a surround speaker system. ���Imaginative immersion��� comes close to the immersion definition used by Brown and Cairns [3], describing absorption in the narrative of a game or identification with a character, which is understood to be synonymous with feelings of empathy and atmosphere. However, atmosphere might be a mix of imaginative immersion and sensory immersion hence, the use of this term in the study conducted by Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. 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Ermi and M��yr�� raises the need for a clearer definition of the concept of atmosphere. Imaginative immersion is held to be most prominent in role-playing games. The dimension of ���challenge- based��� immersion is very close to what Csikszentmihalyi describes as the flow experience [8, 9]. Challenge-based immersion describes the emergent gameplay experience of a player balancing his abilities against the challenges of the game in so far as gameplay is related to motor and mental skills. Challenges in this definition can include different mixtures of physical and mental performance requirements. In the study of Ermi and M��yr�� [11], the game Half-Life 2 (Valve Corporation, 2004) was ranked highest in all dimensions of the SCI model, thus making it a good candidate for studies investigating immersion. The study reported here, based upon Half-Life 2, shows a fluid transition between experiential concepts of immersion and flow. 1.2 Flow The flow model was introduced by Csikszentmihalyi [8] based upon his studies of the intrinsically motivated behavior of artists, chess players, musicians and sports players. This group was found to be rewarded by executing actions per se, experiencing high enjoyment and fulfillment in activity in itself (rather than goals of future achievement, etc.). Csikszentmihalyi describes flow as the ���holistic sensation that people feel when they act with total involvement���. Logically, one could see immersion as a precondition for flow, since immersion involves a loss of a sense of context, while flow describes a level of complete involvement. Csikszentmihalyi specified flow as consisting of several characteristics: balance of challenge and skills, clear goals, explicit feedback, indistinct sense of time, loss of self- consciousness, feeling of enjoyment and control in an autotelic (i.e. self-sufficient) activity. The original flow model was revised by Ellis et al. [10] into a four-channel model, shown in Figure 1, which is used most commonly for describing games and gameplay experience. Defining the balance of skills and challenges is often fuzzy, which led Chen [7] to propose different ���flow zones��� for hardcore and novice players and an optimal intersection, within which the experience converges towards an optimal match of challenges and abilities. However, as a study by Novak et al. [24] shows, there are many different concepts used for studying flow they report 16 flow studies between 1977 and 1996, which all use different concepts and definitions of flow. The only commonly used questionnaire, the flow state scale [16], was designed for sports research and assessed by Kivikangas [17] as usable for game research. In more recent efforts of the EU-funded FUGA (���Fun of Gaming���) project, another better suited scale was developed as part of a game experience questionnaire (GEQ) [15]. Kivikangas was also one of the first to investigate correlations between psychophysiological measures and flow experience, but his results showed flow not to have a significant relationship with psychophysiological measures of basic emotions. 1.3 Psychophysiological measurements Emotions are a vital part of the game experience, motivating the cognitive decisions made during gameplay. Psychophysiological research suggests that at least some emotional states could be quantitatively characterized via measurement of physiological responses. Specific types of measurement of different responses (such as GSR, EMG, ECG and EEG, as described below) are not per se trustworthy signs of well-characterized feelings [4, 5] a de rigueur cross-correlation of all measurements is fundamental to discover the emotional meaning of different patterns in the responses. Furthermore, the often described many-to-one relation between psychological processing and physiological response [6] allows for psychophysiological measures to be linked to a number of psychological structures (for example, attention, emotion, information processing). Using a response profile for a set of physiological variables enables scientists to go into more detail with their analysis and allows a better correlation of response profile and psychological event [6]. The central concern here is the correlation of patterns of measurement characteristics for a set of different measures with subjective characterizations of experience such as emotion and feelings (for example, the feeling of immersion in gameplay). Facial electromyography (EMG) is a direct measure of electrical activity involved in facial muscle contractions EMG provides information on emotional expression via facial muscle activation (even though a facial expression may not be visually observable) and can be considered as a useful external measure for hedonic valence (degree of pleasure/displeasure) [18]. Positive emotions are indexed by high activity at the zygomaticus major (cheek muscle) and orbicularis oculi (periocular muscle) regions. In contrast to this, negative emotions are associated with high activity at the corrugator supercilii (brow muscle) regions. This makes facial EMG suitable for mapping emotions to the valence dimension in the two-dimensional space described in Lang���s dimensional theory of emotion [18]. The valence dimension reflects the degree of pleasantness of an affective experience. The other dimension, the arousal dimension, depicts the activation level linked to an emotionally affective experience, ranging from calmness to extreme excitement. In this kind of dimensional theory of emotion, emotional categories found in everyday language (for example, happiness, joy, depression, anger) are interpreted as correlating with different ratios of valence and arousal, hence being mappable within a two- Skills High Low High Low Challenge Anxiety Apathy Boredom Flow Figure 1. The two-dimensional four-channel model of flow based on Csikszentmihaly and Ellis et al. [8, 10] 82