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Examples of XaviX sport game titles include. Powerboxing, Bowling, Tennis, Baseball, Fishing, and the. Jackie Chan Studio Fitness. Players use the appropriate.
A Theory-based Framework for Evaluating Exergames as Persuasive Technology Marc A. Adams, Simon J. Marshall†, Lindsay Dillon, Susan Caparosa, Ernesto Ramirez, Justin Phillips, Greg J. Norman † San Diego State University Center for Wireless and Population Systems University of California, San Diego 5500 Campanile Dr 9500 Gilman Drive (MC#0811) San Diego, CA 92182 La Jolla, CA 92093 {m1adams, ldillon, scaparosa, erramirez, jphillips, gnorman} @ucsd.edu; [email protected]

ABSTRACT Exergames are video games that use exertion-based interfaces to promote physical activity, fitness, and gross motor skill development. The purpose of this paper is to describe the development of an organizing framework based on principles of learning theory to classify and rank exergames according to embedded behavior change principles. Behavioral contingencies represent a key theory-based game design principle that can be objectively measured, evaluated, and manipulated to help explain and change the frequency and duration of game play. Case examples are presented that demonstrate how to code dimensions of behavior, consequences of behavior, and antecedents of behavior. Our framework may be used to identify game principles which, in the future, might be used to predict which games are most likely to promote adoption and maintenance of leisure time physical activity.

Categories and Subject Descriptors J.4 [Computer Applications]: Social and Behavioral Sciences – psychology, economics.

General Terms Measurement, Design, Economics, Theory.

Keywords Exertainment, Exercise, Physical Activity, Video Games, Behavior Analysis, Operant Theory, Public Health.

1. INTRODUCTION There is growing public health concern over the effects of a sedentary lifestyle on the health of young people, particularly in relation to overweight and obesity. Only 42% of children aged 6-11 years meet the national recommendations for physical activity, and this figure

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drops to 8% as they enter adolescence (CDC, 2007). Similar patterns are evident during adulthood--less than 50% of men and women engage in sufficient amounts of leisure time physical activity (Troiano et al., 2008). Although existing efforts to reverse or attenuate these trends have been only marginally effective, novel applications of technology that promote physical activity appear promising. In particular, there has been much excitement over the use of video games that use exertionbased interfaces (referred to as “exergames”) to promote activity, fitness, and gross motor skill development. Unlike traditional games that promote sedentary activities through mainly thumb and finger movements, exergames often include walking, running, sliding, jumping, throwing, and hitting—gross motor skills that are considered the building blocks of complex movement patterns required in many ‘real world’ sports and exercises. Examples of popular exergames include Dance Dance Revolution (Konami, Japan), Nintentdo Wii Sports (Nintendo, Japan), and XAVIX sports (SSD/XaviX Ltd., Japan). Anecdotal evidence suggests that children and adults enjoy these games, but published empirical data have focused almost exclusively on the energy costs or metabolic responses to playing (Baranowski et al., 2007; Mellecker et al., 2008; Anders,F 2008). Although physiologic and metabolic outcome data are useful for evaluating the health benefits accrued while playing, we do not know why people enjoy these activities, and we have limited understanding of the game-related mechanisms that contribute to continued involvement. Exergames are highly complex and programmed virtual environments with graphics, sounds, rules, and social interactions that often necessitate complex behaviors to play them. Within games, there are multiple levels that often present different types of stimuli, rules, and behavioral requirements—factors that contribute to the “game experience.” The game play experience is often described using phrases that represent affective states that result from playing, such as boring, fun, hard, easy, frustrating, and enjoyable. These emotional states are reactions to the explicit and implicit rules or contingencies embedded in the game’s mechanics. From a health-research perspective, behavioral contingencies represent a theory-based game design principle that can be objectively measured, evaluated, and

manipulated to help explain the frequency and duration of game play over time. Understanding and predicting adoption and adherence patterns of exergame play is important because it may help physical activity professionals better select, prescribe, and promote exergame play for health. Therefore the purpose of our research is to (a) develop an organizing framework based on principles of learning theory to classify and rank games according to embedded behavior change principles, and (b) determine which games or principles are most likely to increase the adoption and maintenance of physical activity.

2. HOW EXERGAMES SHAPE BEHAVIOR. Learning or operant theory is a persuasive teaching technology that promotes learning and behavior change through the use of reinforcement (Fogg, 2003). Operant theory proposes that an individual’s behavioral choices over time are primarily (but not exclusively) a function of the relative reinforcing value of each environmental option (Hursh, 1980). The reinforcing value can be changed by manipulating constraints of the options such as the reinforcer amount, reinforcer immediacy, or the schedule of reinforcer delivery. To understand why certain exergames have high reinforcement value, we need to study what constraints exist within a game and which constraints are associated with individual’s lay terminology of their experience.

2.1 Persuading with Consequences. Operant theory emphasizes shaping of complex behavior through temporal relationships known as contingencies (Cooper, Heron, & Heward, 2006). Contingencies describe the functional relationships between behavior, the stimuli that precede it (antecedents), and the stimuli that follow (consequences). Positive and negative reinforcement both refer to a process of using consequences to increase the probability of behavior. Negative punishment (penalty) and positive punishment refer to a process of using consequences to decrease temporarily the probability of behavior. Exergames shape behavior by using these principles and gradually increasing requirements for earning reinforcers through different schedules of reinforcement. Schedules of reinforcement are implicit or explicit rules that describe the delivery of reinforcement. Each schedule induces unique behavioral patterns and each has known limitations for teaching new behaviors and sustaining existing behavior. For a more detailed description of the specific steady states for basic and multiple schedules, as well as the applied limitations of shaping, the reader is referred to Ferster and Skinner (1957) and Cooper, Heron, & Heward (2006), respectively. Therefore, it is important to identify how consequences and their schedules are used within a game, since game designers program these contingencies with or without an awareness of their effect on behavior.

2.2 Persuading with Antecedents Game play behavior also comes under the influence of antecedents. Antecedent stimuli occur before behavior and can be used to instruct or model new behavior or be used as discriminative stimuli that signal a change in consequences or behavioral requirements. Rules -- instructions, advice, and commands -- act as antecedent stimuli. Thus, rules describe contingencies, either explicitly or implicitly. For example, in a boxing game, a player might be instructed with on-screen text to “punch the bag where the target points” (discriminative stimulus) which will result in an unannounced positive outcome (consequence); if the player then follows the instruction by punching at the appropriate time and place, the player earns points, positive visual and auditory feedback, praise, or other outcomes. Additionally, video games use real or virtual characters who demonstrate desirable behavior and how to play games. Behavioral modeling is a mechanism for learning new behaviors common to social learning theory (Bandura, 1986). For example, to learn a new move or to be successful in a game, an individual must imitate or match their behavior to the model’s behavior (match to sample). Matching one’s behavior to the model’s sample can result in positive and negative reinforcement.

3. DEVELOPING A THEORETICAL FRAMEWORK TO IDENTIFY AND CODE CONTINGENCIES IN GAMES. Although game environments are very reliable virtual environments, the graphics, music, sounds, rules, behavioral requirements, and social interactions vary within and between games. Within each game, multiple levels can exist and each level presents multiple types of stimuli, rules, and behavioral requirements. Game designers program these stimuli, their functional effects, and the behavioral requirements for specific purposes, with or without knowledge of their influence on adoption and maintenance of game play and emotional states. The complex nature of games, and the number, types, and temporal order of stimuli can be overwhelming without a clear theoretical foundation and operational definitions of concepts. A theoretical framework is lacking that is rich in behavioral concepts and able to classify the temporal nature and function of game stimuli to explain and ultimately influence adoption and maintenance of physical activity and game play. We will now discuss the important elements of the operant-theory framework.

3.1 Behavior and its dimensions. Exergames teach users to perform various physical activity behaviors (e.g. stepping, dancing, sliding, swinging, hitting, etc.) that form the foundations of many sport and exercise behaviors. Moreover, through interactions with the contingencies over time, games cause players to change the form, frequency, rate, intensity, response time, or duration of these responses. For example, after a few attempts new players may learn that a game does not differentially reinforce the intensity at which a punch is thrown.

Alternatively, experienced players may be aware that a game requires punching at a very high rate to win, yet they might make an error early in the chain of responses and, as a result, not meet the behavioral requirement. After many practice trials, the game should teach players to avoid critical errors early on to reach the behavior requirement. The game shapes players’ behavior by allowing only certain qualities of behavior to control it. These qualities can be described as dimensions of behavior. The dimensions of behavior important to health scientists and game designers are topography, frequency, rate, intensity, latency, and duration (Cooper, Heron, & Heward, 2006). Topography refers to the form of the behavior or ‘what the behavior looks like’. This can be as simple as the repertoire of racquet movements possible in a tennis exergame, such as a forehand, a smash, and a volley. Frequency refers to the number of times a behavior occurs. Rate refers to frequency within a specified period. Rates of behavior can be reported as "responses per second" (e.g. punches per second), "responses per minute," or "responses per day." Intensity refers to the strength or force with which a behavior is emitted. Some games may discriminate and differentially reinforce the force of a player’s swing or punch. Latency refers to the time between a signal or prompt for a response and the incidence of the behavior. Response time tests or games that improve speed are good examples of changing (decreasing) latency. Duration refers to the time from the beginning (onset) to the end (offset) of a response without interruption. Games that require a player to dance for longer and longer intervals without stopping would be an example increasing the duration of behavior.

3.2 Behavioral Contingencies in Exergames The unit of analysis for our framework is a contingency. Many contingencies exist within video games. Once a behavior is identified, contingencies can be identified by starting with the simplest type: a two-term contingency. Two-term contingencies are comprised of 1) a behavior and 2) a consequence. For example, in a boxing exergame, when a player punches (behavior) an object, the game may present or remove stimuli, such as the presentation of a red flash, an audible sound, a verbal statement, and/or the presentation of points. The flash, sound, statement, and change in points all occur after the behavior and are therefore consequences. In our example, one punch (behavior) caused all four of the consequences (flash, sound, statement, and point). Thus, one response can also have multiple consequences. It is important to identify and describe all consequences. Reinforcement that occurs every time a behavioral requirement is met is on a continuous ratio schedule of reinforcement. Behavior can also be reinforced intermittently using fixed or variable schedules. Reinforcement can be based on the number of responses (ratio); the first behavior after a period of time (interval); the continuous performance of behavior over time (duration), among others. Thus, basic schedules include fixed ratio, variable ratio, fixed interval, variable interval,

fixed duration, and variable duration (Ferster and Skinner, 1957; Cooper, Heron, & Heward, 2006). For fixed ratio schedules, a behavior is reinforced after it has occurred a fixed number of times. For example, a player might earn 100 points once they have successfully jumped over three successive barriers. For variable schedules, the schedule specifies the responses on average. For example, a game designer might program 100 points to be earned each time a player successfully jumped over 3 barriers on average, but the points could occur after the player’s first jump or their tenth jump. Games also present stimuli that precede a response; these are known as antecedent stimuli. Thus, the expansion to a 3-term contingency comprised of antecedent-behaviorconsequence relationships. Antecedents can include onscreen instructions, behavioral modeling of the desired response, or images or sounds that signal the player when there will be changes to the consequences for a behavior. For example, the game may present an image of a virtual player punching a bag to demonstrate types of punches or where to aim (modeling). Alternatively, the game may present a special word that signals to the player that their future behavior will result in a different amount of points or special access to a new level (change in consequences).

3.3 What’s Not a Game Contingency. Some stimuli in video games change, but that change is not related to a player’s behavior. In addition, some stimuli remain constant throughout the game. For example, during the game, there may be background audience applause. The audience applause does not change as a result of anything the player does. Or the applause varies, but not as a function of the player’s behavior. Therefore, any game stimuli that is constant, or changes but that change is not contingent on some dimension of the player’s behavior, is not considered a game contingency.

4. METHOD OF CODING VIDEO GAMES. A framework of operant mechanisms in games including many possible antecedents, behavioral dimensions, and consequences was operationalized and documented (available from the first author). Figure 1 provides a sample of the operational definitions and examples. Definitions for the following terms were included: response, response class, stimulus, antecedent, consequences, topography, frequency, rate, intensity, latency, duration, positive reinforcement, negative reinforcement, positive punishment, penalty/response cost (negative punishment), change in reinforcement amount, change in punishment amount, latency of reinforcement, latency of punishment, reinforcement schedules (fixed ratio, fixed interval, fixed duration, variable ratio, variable interval, variable duration). The framework also instructs how to organize the coding of video games. Once the theoretical framework was developed to identify and code game contingencies, game play was recorded and data coders were trained.

A research assistant was instructed to play a game including all levels. Game play was recorded using a DVDR recorder. The assistant tested and recorded multiple outcomes in each game. For example, the player recorded what occurred in the game for a correct player response, an incorrect response, and no response. Once the assistant had developed a comprehensive sample of game play, game stimuli were then coded. Table 1. A sample of the operational definitions developed for the framework.

The first author [MA], a behavioral scientist with expertise in operant theory, coded the first game and described behavioral dimensions and game stimuli that changed as a function of the player’s behavior. Descriptions of every observed game contingency were recorded. For example, “Each time a player hits a red ball, the game presents 1 point increase in the score” or “Before player starts punching, the game presents an image of virtual player hitting a red ball to score points.” The coder identified and described stimuli and their function on behavior for each game. This resulted in several hundred statements. If the coder noticed an aspect of the game that needed further exploration, a research assistant was asked to explore and record that aspect of the game. Once coding of the first game was complete, training of new coders was conducted by having them identify and code behavioral dimensions and contingencies for the game coded by the expert coder, with the goal of matching the first author. The training of new coders was complete when they agreed with the expert coder on greater than 85% of the stimuli and contingencies captured. However, if new coders identified behavioral dimensions or contingences missed by the first coder, these were reviewed and verified by both parties. A master list of dimensions and contingencies was developed for each game. After training, for each subsequent game, two research assistants coded each game independently resulting in every game being coding twice in entirety, with inter-observer agreement measured repeatedly at multiple points for each game. Disagreements in coding were resolved by consensus after reviewing the game multiple times, with the master list refined where appropriate. Depending on the console system and specific game, we have noticed that specific game titles can have multiple subgames (e.g. A bowling game title may include 4 subgames: 3 training games and tournament mode) with multiple levels for each subgame. Moreover, multiple hierarchical levels of contingences can occur within each subgame. Because of the difficulty in describing multiple

levels of contingency analysis and multiple subgames with levels, we chose to adopt a multi-level analysis terminology that was independent of game design. The term “Contingency Point (CP)” refers to a discrete temporal point (a stop in play) where game designers programmed consequences. CP0 includes all of the antecedents-response-consequence relationships that occur for single responses on a moment-to-moment basis while actively playing a game without a discrete stop in play. The behavior and contingencies of interest are the individual responses (e.g. each punch, swing, bowl) and the immediate antecedents and consequences before and after response (e.g. sounds, points, flashes). CP1 is the first discrete break in game play and is considered a second level of contingency analysis. A cumulative behavior requirement (chain or bout of responses) and a temporary or permanent stop in the game are indicators of this level of analysis. Contingencies at CP1 present antecedents and consequences before and after a bout of continuous play (e.g. instructions and modeling of behavior before play begins, and, after a bout of play occurs, the stimuli presented/removed such as points, rankings, or verbal statements). For example, the game stops play to award a player a point or advance them from level 1 to level 2. Sometimes the advancement of levels/rounds is used as a consequence and occurs without a discrete break in game play. In these cases, we coded them as CP0. Contingency Point 2 (CP2) is the next discrete break in game play, within which CP0 and CP1 is nested. Depending on the specific game, there may be as many as five Contingency Points, and there may be multiple occurrences of each contingency point in different levels of a game. A matrix of the qualitative data was used to code each raw statement from the master list of descriptions. In the first column, each coding statement was listed. Subsequent columns were used to code the game title name, subgame name (e.g., Moving Pins), contingency point, antecedents, behaviors, and consequences and their specific types. For behaviors, the coder described if the game changed one or more behavioral dimensions: topography, frequency, rate, intensity, latency, or duration of responses, as well as how the game changed these dimensions by measuring the dimensions across game levels. For stimuli that occurred before and after the behavior, the coder used two super ordinate subheadings: Antecedents and Consequences. For antecedents, each statement was then coded using one or more of the following concepts: discriminant stimulus, prompt, verbal instruction, or behavioral modeling. For consequences, each statement was coded using one or more of the following concepts: positive reinforcement, negative reinforcement, positive punishment, response cost (negative punishment), change in reinforcement amount, change in punishment amount, latency of reinforcement, latency of punishment, reinforcement schedule (fixed ratio, fixed interval, fixed duration, variable ratio, variable interval, variable duration). Depending on its function, one statement could qualify for multiple codes. Specific definitions of these concepts were developed from comprehensive texts on operant conditioning (e.g., Cooper et al., 2006; Chance, 1999).

Once lay descriptions of contingencies have been coded with the appropriate principles, we can begin to examine how games may vary in their use of specific concepts. The most basic data would be descriptive statistics on the use of each concept for each subgame within a game title and for an entire game title. If objective data on physical activity e.g. via accelerometry) or emotional state (e.g. self-report or direct observation) were available in a time-series, it would enable us to correlate the moment-to-moment prevalence of specific contingencies with those intrapersonal events. Such analysis might reveal which game-based behavior change concepts or combinations of concepts were associated with adoption and maintenance of physical activity, or emotional states such as boredom, frustration, and enjoyment.

4.1 Case Examples of Coding Methodology.

that is needed to block an opponent’s punches during tournament play. The most basic part of this topography is the player putting their gloves together in front to form a block. Engaging in blocking behavior right and left, up and down, and through other combinations further expands the forms of blocking taught to players. Figure 1 shows a screenshot of Panel Toucher. Players see an outline of nine panels displayed in a 3x3 matrix. The game highlights panels in chained combinations and the player must put his/her gloves together and pass over the panels on the screen in the same order that the panels are presented. Figure 2 shows that there are 20 different chained topographies of blocking that are taught. Although some look similar, the stating and ending points are different. Panel Toucher also increases the rate of touching panels from levels 1 to 10, starting at 1.73 panels per second to 3.6 panels per second (on average), respectively.

This analysis focuses on coding of contingencies that occur in the XaviXPORT exergame console system (SSD/XaviX Ltd., Japan). The XaviXPORT system is a game cartridge port that connects to a television. Game cartridge applications come with wireless controllers that approximate actual sporting equipment (e.g. boxing gloves, tennis racket). Examples of XaviX sport game titles include Powerboxing, Bowling, Tennis, Baseball, Fishing, and the Jackie Chan Studio Fitness. Players use the appropriate sporting equipment and their body movements to control all aspects of the game play.

4.1.1 Coding Dimensions of Behavior. To demonstrate the coding framework and data collection, we present a number of examples from our own coding.

Figure 1. Xavix Powerboxing screenshot of the Panel Toucher game.

Powerboxing is one of the XaviX sport games. In Powerboxing there are tournament and exhibition modes and a number training games. Punchfast is one of the training games. We observed that this game appears to shape a player’s behavior to punch faster across levels. This would be a dimension of rate. Table 2 shows that after collecting data on each level we discovered that that game shapes higher rates of punching over 10 levels, ranging from 2.0 to 6.67 punches per second on average. The reason for increasing the rate of punching is determined by the game designers, but may be to approximate real boxing or to teach players the requirements for tournament play later in the game.

Figure 2. Topographies (forms) of blocking behavior shaped by Xavix Powerboxing.

Table 2. Shaping the rate of punching across 10 levels in the Powerboxing Punchfast game. Level Hits Time Rate per second 1 20 10 2.00 2 25 10 2.50 3 45 15 3.00 4 55 15 3.67 5 80 20 4.00 6 90 20 4.50 7 125 25 5.00 8 140 25 5.60 9 180 30 6.00 10 200 30 6.67 Another Powerboxing training game is called Panel Toucher. This game teaches player’s ‘blocking topography’

Another Powerboxing game is called Combination Training. This game teaches players various ‘punching typographies’ (right jab, left jab, right hook, and left hook). These four forms of a punch are the most basic topographies. The four topographies can be chained together to create a combination of punches. Figure 3 shows how players must match their punching behavior to the topography of punches displayed on the top of the screen.

Figure 3. Xavix Powerboxing screen shot of the Combination Training game.

4.1.2 Coding Consequences of Behavior. Games teach behavior by using consequences contingent on specific dimensions of the player’s responses. The types stimuli that games use as consequences are broad and include changes in visual and auditory stimuli, social statements (such as praise or criticism), advancement/demotion of levels, points, presentation or removal of special items, etc. We present a number of examples of how Xavix games use consequences. Xavix Bowling is a game that includes regular bowling and tournament modes along with three training games. One training game is called Moving Pins. The game is unusual in that it requires the players to bowl on an extra large lane with pins moving across the screen from both sides. Players must knock over white and gold pins before they fall off the lane, while simultaneously avoid hitting black pins. Figure 4 shows a screen shot of the game. The following is an example of a CP0 contingency for Xavix’s Bowling subgame, Moving Pints: Each time the player knocks down one gold bowling pin, the game presents: 1. 2. 3. 4.

an increment of 120 points. an ‘energizing sound’. the statement “SUPERMODE”. the cumulative number of gold pins that are knocked down during the entire game.

In this example, we can see four consequences contingent on knocking over a gold pin. The increment of 120 points, the increment of 1 count on the cumulative counter of gold pins, and the energizing sound are all feedback associated with correct behavior. Because each of these stimuli can be considered “desirable” and were presented (rather than aversive game stimuli being removed), these consequences would be classified as positive reinforcers. The presentation of the word “SUPERMODE” is also associated with a change in game state; the game temporarily slowed the fast movement of pins (removed an aversive state of the game). Thus, SUPERMODE can be classified as a negative reinforcer for knocking down gold pins. Moreover, we determined that these consequences occur each time a player knocks down a gold pin. Therefore, we know that for each of the four consequences the game is using a continuous schedule of reinforcement (a special case of a ratio schedule). Now let’s consider the following CP1 example for Punchfast in Powerboxing. The behavior requirement to successfully complete level 7 is 125 punches on a boxing bag in 25 seconds (a rate of 5 punches per second, on average). If player passes level requirement, the game presents: 1. 2. 3. 4. 5. 6.

The statement “Succeeded!” ‘Applause’ sound. A ‘victory’ sound. A gold star. An image of Jackie Chan giving the player a ‘thumbs up’. Jackie Chan saying one of three different statements (e.g. “How did you become so fasthanded?!”).

If the player passes the level requirement, we can see that six unique stimuli are presented. Because each of these stimuli was presented and can be considered desirable, these consequences can be classified as positive reinforcers. They also occur each time a player passes the level requirement. It should be noted that advancement through the levels was not contingent upon meeting the behavioral requirement -- a player could start at level 10 – and so advancement is not a consequence for this game. Punishment is also used in the Xavix games. If the player failed to pass the behavioral requirement for the level, the game presents: 1. 2. 3. 4. 5.

Figure 4. Xavix Bowling game screenshot of the Moving Pins game.

The statement, “Failed!” A ‘do do do’ sound effect. A gray star. An image of Jackie Chan with his ‘fists up’ in a defensive position. Jackie Chan saying one of three different statements (e.g. “Keep your punches tight and accurate!”).

In this example, five stimuli are presented. Since the failure message and the aversive sound effect are presented, and are generally negative stimuli that would result in a decrease in the undesirable behaviors performed

(errors during play), these two can be classified as positive punishers. The gray star is really the absence of a gold star, and since gray is not associated with reinforcement, it could be classified as withholding reinforcement or removal of a reinforcer (we believe it is the former). The image of Jackie Chan with his fists up in a defensive position and his instruction about how to perform better may be classified as undesired instructional feedback on the player’s behavior (positive punishment) or as an antecedent instruction on how to perform better in the future.

4.1.3. Coding Antecedents of Behavior. In addition to the consequences games present, games also present stimuli before behaviors occur. As noted earlier these stimuli can be verbal instructions, behavioral modeling, and/or some other stimuli that functions as a signal to players that specific behaviors will be reinforced or punished. Xavix Tennis is another game that includes exhibition and tournament modes, as well as three training games. Serving Aces is one of the training games. The object is to develop a serving topography. To teach players how to serve, the game presents a number of on-screen instructions. Figure 5 shows a screen shot of Serving Aces. The instructions include “Push the button to toss the ball” and “Swing the racquet” followed by “Where the arrow is pointing.” These instructions are presented before the player can perform the required action. A player who pushes the button to toss the ball and then swings the racquet at the correct time will successfully hit the ball over the net (a reinforcing consequence). Before the player has a chance to practice their swing, the tennis game simulates the movement required and gives auditory feedback during those actions. One could easy visualize a real or virtual image of a player performing the serve.

Figure 5. Xavix Tennis game screenshot of the Serving Aces game. Discriminative stimuli are also part of game play. Discriminative stimuli occur before behavior and signal that consequences are now available for performing certain behaviors. For example, in bowling the presentation of the word “SUPERMODE” -- in addition to this word being associated with a change in the speed of bowling pin movement -- was associated with a second consequence: it increased the point values of pins for the next 7 seconds of the game. Thus, SUPERMODE functions as both a

negative reinforcer (knocking down gold pins results in the consequence of slower pin movements) and it functions as a signal that if the player were to knock down white or gold pins over the next 7 seconds, those pins would be worth bonus points. As predicted by operant theory, one stimulus can sometimes have multiple consequence and antecedent functions.

5. DISCUSSION/CONCLUSIONS This article described the background and development of a tool to identify and classify learning theory principles in exergames. Case examples were presented that demonstrate the coding of dimensions of behavior, consequences of behavior, and antecedents of behavior. These samples reveal that many theoretically supported mechanisms are used to influence game playing behavior. Understanding how these mechanisms influence game play can have important implications for the adoption and maintenance of physical activity and individuals’ choice of playing an exergame versus a sedentary alternative (e.g., television viewing). Players’ affect-based descriptions of games, such as, fun, unpredictable, hard, etc. may be explained and possibly changed by manipulating aspects of the game. One could foresee game designers and health researchers working together to promote long-term physical activity habits by manipulating game contingencies, such as changing games to use intermittent schedules of reinforcement, gradually increasing behavioral requirements needed to earn reinforcers, or by providing unique reinforcers that appeal to specific demographic groups (e.g. men, women, youth, older adults, etc.). Slot machines used in casinos use contingencies to get players to adopt and continue their gambling behavior. Contingencies used in gambling machines may be an ideal model for game researchers. The next step in this research is to incorporate the coding into an Exergame Typology. The typology will be used to classify exergames along several dimensions such Easy to Learn, Challenge to Win, or Realistic to Play. The typology will be operationalized from the antecedent, behavior dimensions, and consequences identified in the exergame. From this typology researchers would be able to formulate and test hypotheses about how exergames with different typology profiles should be related to adoption and maintenance of physical activity. For example, one could hypothesize that an exergame categorized as Challenging to Win would include levels that shape very quick reaction times, high rates, or long durations of behavior. This could be done through the use of gradually increasing the behavioral requirements or through the use of variable schedules of reinforcement. Additionally, one could hypothesize that a sport exergame that approximates reality in its rate or topography of behavior is important for sustaining play for adults but not for children. Alternatively, games labeled “Hard to Learn” may include behavior requirements that are too difficult to reach early on, lack sufficient modeling or instructions, or use too many aversive stimuli. Testing these hypotheses in experimental studies would further our understanding of

exergame play and serve to validate and refine the Exergame Typology.

[2] Bandura A. 1986. Social Foundations of Thought and Action. Englewood Cliffs, NJ: Prentice-Hall.

The ultimate goal of this research is to identify highly rewarding games and game components that have the greatest chance of success when competing with many alternative sedentary options such as television viewing and computer and video games that require low levels of energy expenditure. This could be how exergames are identified to have the greatest public health impact on obesity. Studies have demonstrated that while most exergames tend to result in modest levels of energy expenditure (e.g., Tan et al 2002), the metabolic cost is greater than traditional sedentary activities (e.g., Lanningham-Foster et al., 2006). Thus, even modest energy expenditure from exergames can be an important contributor to overall energy balance when time spent playing exergames replaces time spent engaging in sedentary behaviors. However, we hypothesize that regardless of the energy expenditure during exergame play, it is the behavioral principles within the game that will determine its ability to sustain interest and game play for extended periods.

[3] Baranowski, T., Buday, R., Thompson, D.I., Baranowski, J., 2008. Playing for real: video games and stories for health-related behavior change. Am. J. Prev. Med. 34, 1(Jan. 2008), 74-82.

Understanding the behavioral principles in exergames can also inform game developers how to create engaging exergames for specific purposes (e.g., weight loss) or for specific target population segments (e.g., adolescents, older adults). This may result in game players’ behavior becoming generalized to ‘real life’ activities. For example, what instructions, modeling, behavioral dimensions, or consequences should be included in a tennis exergame if the goal is to teach people the skills needed to play real tennis? Finally, exergames may serve as a ‘controlled’ environment where behavior principles could be manipulated (such as by varying the schedule of reinforcement) to better understand how to influence adoption and maintenance of physical activity.

[9] Hursh, S.R. Economic concepts for the analysis of behavior. 1980. Journal of the Experimental Analysis of Behavior, 34, 219-238.

6. ACKNOWLEDGMENTS This work was supported in full by a grant from the Robert Wood Johnson Foundation’s Health Games Research (#414804).

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