Reciprocity on the Hardwood: Passing Patterns among Professional Basketball Players

Past theory and research view reciprocal resource sharing as a fundamental building block of human societies. Most studies of reciprocity dynamics have focused on trading among individuals in laboratory settings. But if motivations to engage in these patterns of resource sharing are powerful, then we should observe forms of reciprocity even in highly structured group environments in which reciprocity does not clearly serve individual or group interests. To this end, we investigated whether patterns of reciprocity might emerge among teammates in professional basketball games. Using data from logs of National Basketball Association (NBA) games of the 2008–9 season, we estimated a series of conditional logistic regression models to test the impact of different factors on the probability that a given player would assist another player in scoring a basket. Our analysis found evidence for a direct reciprocity effect in which players who had “received” assists in the past tended to subsequently reciprocate their benefactors. Further, this tendency was time-dependent, with the probability of repayment highest soon after receiving an assist and declining as game time passed. We found no evidence for generalized reciprocity – a tendency to “pay forward” assists – and only very limited evidence for indirect reciprocity – a tendency to reward players who had sent others many assists. These findings highlight the power of reciprocity to shape human behavior, even in a setting characterized by extensive planning, division of labor, quick decision-making, and a focus on inter-group competition.     

Selfish Play Increases during High-Stakes NBA Games and Is Rewarded with More Lucrative Contracts

High-stakes team competitions can present a social dilemma in which participants must choose between concentrating on their personal performance and assisting teammates as a means of achieving group objectives. We find that despite the seemingly strong group incentive to win the NBA title, cooperative play actually diminishes during playoff games, negatively affecting team performance. Thus team cooperation decreases in the very high stakes contexts in which it is most important to perform well together. Highlighting the mixed incentives that underlie selfish play, personal scoring is rewarded with more lucrative future contracts, whereas assisting teammates to score is associated with reduced pay due to lost opportunities for personal scoring. A combination of misaligned incentives and psychological biases in performance evaluation bring out the “I” in “team” when cooperation is most critical.     

A longitudinal analysis of technical-tactical and physical performance of the teams in the Spanish LaLiga Santander: An eight-season study

The aim of this study was to describe in the way teams played for the last eight seasons (from 2011–12 to 2018–19) in the Spanish Football First Division (Spanish LaLiga Santander), taking into account team match performances (n = 5,518). Ten technical-tactical and physical variables grouped into five dimensions were used: final behaviour (shots and crosses), set piece (corners and fouls), match volume (passes), physical performance (total distance covered) and collective use of the space (team width, team length, team defence height and distance from the goalkeeper to their defence). The main results were that the number of passes and team width showed a stable trend as the seasons passed. Nevertheless, the number of shots, crosses and corners, total distance covered, team length and distance from the goalkeeper to their defence showed a descending trend. The main conclusion was that over the seasons studied, the Spanish LaLiga Santander teams were characterized by an indirect style of play that, being the usual in this league, presented some evolution. The trend in the evolution of the game is that defence is put before attack. The findings of the study may be of interest to professional football staff to know more about the particular way teams play in competition, as well as its evolution, so as to focus on the training process according to the trend that is taking place in the game.     

Predicting performance and injury resilience from movement quality and fitness scores in a basketball team over 2 years

The purpose of this study was to see if specific tests of fitness and movement quality could predict injury resilience and performance in a team of basketball players over 2 years (2 playing seasons). It was hypothesized that, in a basketball population, movement and fitness scores would predict performance scores and that movement and fitness scores would predict injury resilience. A basketball team from a major American university (N = 14) served as the test population in this longitudinal trial. Variables linked to fitness, movement ability, speed, strength, and agility were measured together with some National Basketball Association (NBA) combine tests. Dependent variables of performance indicators (such as games and minutes played, points scored, assists, rebounds, steal, and blocks) and injury reports were tracked for the subsequent 2 years. Results showed that better performance was linked with having a stiffer torso, more mobile hips, weaker left grip strength, and a longer standing long jump, to name a few. Of the 3 NBA combine tests administered here, only a faster lane agility time had significant links with performance. Some movement qualities and torso endurance were not linked. No patterns with injury emerged. These observations have implications for preseason testing and subsequent training programs in an attempt to reduce future injury and enhance playing performance.     

THE RELEVANT USE OF THE TRADITIONAL TUNISIAN GAME ‘‘RAQASSA’’ FOR CARDIOVASCULAR STIMULATION IN SCHOOLCHILDREN

The aim of this study was to investigate the heart rate (HR) responses, the rate of perceived exertion (RPE), and the feeling during physical education schooling while performing traditional games activities compared to intermittent exercise. Nineteen pre-pubertal children randomly performed on different days two types of lessons (intermittent running mode vs. traditional Tunisian “Raqassa” game) lasting 12-min each. HR was continuously recorded during both lessons, while ratings of perceived exertion and Feeling values were recorded after the sessions. The mean HR value during the traditional game was significantly higher than during intermittent exercise (p<0.05). Conversely, the perceived exertion score was significantly higher after intermittent exercise than the traditional exercise game (p<0.05), showing that the higher cardiovascular strain of the game was perceived as “lighter” than the run. Simultaneously, the children''s Feeling was significantly higher after the traditional game than intermittent exercise (p<0.001), showing a higher satisfaction from playing with respect to running. Exercise based on the “Raqassa” traditional game could be used in pre-pubertal children as an alternative or as an additional method for suitable cardiovascular stimulation during physical education lessons with lower perceived exertion and better feeling compared to intermittent running.     

Osmosensitivity of Sucrose Uptake by Immature Pea Cotyledons Disappears during Development

Sucrose uptake was studied in isolated, immature pea cotyledons (Pisum sativum L. cv Marzia) in relation to their developmental stage. During the developmental period examined the water content of the cotyledons decreased from ≈80% “stage 1” to ≈55% “stage 2”. When assayed in an isotonic medium (400 osmoles per cubic meter) the influx capacity per gram fresh weight for sucrose was almost constant during this developmental period. The influx could be analyzed into a saturable component (K_m ≈ 9 moles per cubic meter; V_max ≈ 150 nanomoles per minute per gram fresh weight) and an unsaturable component (k_i ≈ 0.5 nanomoles per minute per gram fresh weight [per mole per cubic meter]). Incubation in a hypotonic medium reduced the sucrose influx in stage 1 cotyledons, up to 80% reduction at 0 milliosmole (medium without mannitol), but had no effect on sucrose uptake by stage 2 cotyledons. Reduced uptake in a hypotonic medium (100 osmoles per cubic meter) could be attributed to a lowering of the V_max from 150 to 36 nanomoles per minute per gram fresh weight. During incubation of stage 1 cotyledons and stage 2-cotyledons in a hypotonic medium (200 osmoles per cubic meter) their volume increased by 16% and 5.6%, respectively, while the calculated turgor pressure increased from 0.2 to 0.6 megapascal for cotyledons of both developmental stages. Reduced sucrose influx in hypotonic medium, therefore, seems to be related to cell swelling (membrane stretching) rather than to increased turgor pressure.     

Basketball Teams as Strategic Networks

We asked how team dynamics can be captured in relation to function by considering games in the first round of the NBA 2010 play-offs as networks. Defining players as nodes and ball movements as links, we analyzed the network properties of degree centrality, clustering, entropy and flow centrality across teams and positions, to characterize the game from a network perspective and to determine whether we can assess differences in team offensive strategy by their network properties. The compiled network structure across teams reflected a fundamental attribute of basketball strategy. They primarily showed a centralized ball distribution pattern with the point guard in a leadership role. However, individual play-off teams showed variation in their relative involvement of other players/positions in ball distribution, reflected quantitatively by differences in clustering and degree centrality. We also characterized two potential alternate offensive strategies by associated variation in network structure: (1) whether teams consistently moved the ball towards their shooting specialists, measured as “uphill/downhill” flux, and (2) whether they distributed the ball in a way that reduced predictability, measured as team entropy. These network metrics quantified different aspects of team strategy, with no single metric wholly predictive of success. However, in the context of the 2010 play-offs, the values of clustering (connectedness across players) and network entropy (unpredictability of ball movement) had the most consistent association with team advancement. Our analyses demonstrate the utility of network approaches in quantifying team strategy and show that testable hypotheses can be evaluated using this approach. These analyses also highlight the richness of basketball networks as a dataset for exploring the relationships between network structure and dynamics with team organization and effectiveness.     

An Ecological Approach to Prospective and Retrospective Timing of Long Durations: A Study Involving Gamers

To date, most studies comparing prospective and retrospective timing have failed to use long durations and tasks with a certain degree of ecological validity. The present study assessed the effect of the timing paradigm on playing video games in a “naturalistic environment” (gaming centers). In addition, as it involved gamers, it provided an opportunity to examine the effect of gaming profile on time estimation. A total of 116 participants were asked to estimate prospectively or retrospectively a video game session lasting 12, 35 or 58 minutes. The results indicate that time is perceived as longer in the prospective paradigm than in the retrospective one, although the variability of estimates is the same. Moreover, the 12-minute session was perceived as longer, proportionally, than the 35- and 58-minute sessions. The study also revealed that the number of hours participants spent playing video games per week was a significant predictor of time estimates. To account for the main findings, the differences between prospective and retrospective timing are discussed in quantitative terms using a proposed theoretical framework, which states that both paradigms use the same cognitive processes, but in different proportions. Finally, the hypothesis that gamers play more because they underestimate time is also discussed.     

The relationship between violent video games,acculturation, and aggression among Latino adolescents

Multiple factors are involved in the occurrence of aggressive behavior. The purpose of this study was to evaluate the hypotheses that Latino middle school children exposed to higher levels of video game playing will exhibit a higher level of aggression and fighting compared to children exposed to lower levels and that the more acculturated middle school Latino children will play more video games and will prefer more violent video games compared to less acculturated middle school Latino children. This study involved 5,831 students attending eight public schools in Texas. A linear relationship was observed between the time spent playing video games and aggression scores. Higher aggression scores were significantly associated with heavier video playing for boys and girls (p < 0.0001). The more students played video games, the more they fought at school (p < 0.0001). As Latino middle school students were more acculturated, their preference for violent video game playing increased, as well as the amount of time they played video games. Students who reported speaking more Spanish at home and with their friends were less likely to spend large amounts of time playing video games and less likely to prefer violent video games (p < 0.05).     

A Biotic Game Design Project for Integrated Life Science and Engineering Education

Engaging, hands-on design experiences are key for formal and informal Science, Technology, Engineering, and Mathematics (STEM) education. Robotic and video game design challenges have been particularly effective in stimulating student interest, but equivalent experiences for the life sciences are not as developed. Here we present the concept of a "biotic game design project" to motivate student learning at the interface of life sciences and device engineering (as part of a cornerstone bioengineering devices course). We provide all course material and also present efforts in adapting the project''s complexity to serve other time frames, age groups, learning focuses, and budgets. Students self-reported that they found the biotic game project fun and motivating, resulting in increased effort. Hence this type of design project could generate excitement and educational impact similar to robotics and video games.

This Education article is part of the Education Series.

Hands-on robotic and video game design projects and competitions are widespread and have proven particularly effective at sparking interest and teaching K–12 and college students in mechatronics, computer science, and Science, Technology, Engineering, and Mathematics (STEM). Furthermore, these projects foster teamwork, self-learning, design, and presentation skills [1,2]. Such playful and interactive media that provide fun, creative, open-ended learning experiences for all ages are arguably underdeveloped in the life sciences. Most hands-on education occurs in traditionally structured laboratory courses with a few exceptions like the International Genetically Engineered Machine (iGEM) competition [3]. Furthermore, there is an increasing need to bring the traditional engineering and life science disciplines together. In order to fill these gaps, we present the concept of a biotic game design project to foster student development in a broad set of engineering and life science skills in an integrated manner (Fig. 1). Though we primarily discuss our specific implementation as a cornerstone project-based class [4], alternative implementations are possible to motivate a variety of learning goals under various constraints such as student age and cost (see supplements for all course material).Open in a separate windowFig 1We developed a bioengineering devices course that employed biotic game design as a motivating project scheme. A: Biotic games enable human players to interact with cells. B: Conceptual overview of a biotic game setup. C: Students built and played biotic games. Image credits: A C64 joystick by Speed-link, 1984 (http://commons.wikimedia.org/wiki/File:Joystick_black_red_petri_01.svg); Euglena viridis by C. G. Ehrenberg, 1838; C Photo, N. J. C.Biotic games are games that operate on biological processes (Fig. 1) [5]. The biotic games we present here involve the single-celled phototactic eukaryote, Euglena gracilis. These microscopic organisms are housed in a microfluidic chip and are displayed in a magnified image on a video screen. Players interact with these cells by modulating the intensity and direction of light perpendicular to the microfluidic chip via a joystick, thereby influencing the cells’ phototactic motion. Software tracks the position of individual euglena with respect to virtual objects overlaid on the screen, creating myriad opportunities for creative game design and play. For example, in a simple game, points might be scored when a cell hits a virtual box (see S1 Video).The biotic game design project we developed was intended to motivate all the broad categories of theoretical and hands-on skills for creating any integrated instrument intended to house and to interface with biological materials, i.e., optics, electronics, sensing, actuation, microfluidics, fabrication, image processing, programming, and creative design. We termed the synthesis of these skills “biotics” in analogy to mechatronics. Our intended audience for this course was bioengineering undergraduate students at Stanford University who already had some programming experience but little to no experience in device design, fabrication, and integration. We also incorporated bioethics into the curriculum to emphasize the social responsibility of every engineer and demonstrate the potential for the biotic game project to motivate multiple fields. The course we taught spanned ten weeks, divided roughly equally into a set of technical units and the biotic game project, with two 4-hour lab sections and a single 1.5-hour lecture each week. For details and all course documents, please refer to the supplemental material.The technical section of the course focused on developing hands-on skills and theoretical understanding related to devices in a conventionally structured laboratory setting. We introduced students to fundamental electronics concepts and components such as voltage, current, resistors, capacitors, LEDs, filters, operational amplifiers, motors, microcontrollers (Arduino Uno), and breadboards. We followed a similar traditional approach in introducing optics, presenting the thin lens equation, ray tracing, conjugate planes, basic optical system design, and Köhler illumination. We covered additional topics in less detail: MATLAB programming, particle tracking, computer-aided design (CAD), fabrication, and microfluidics (learning objectives are provided at the beginning of each unit in the supplemental material).During the project-based section, students built their own biotic games. We left specific choices of implementation, architecture, and design to the students to encourage creativity and exploration but required students to revisit the technical skills they learned in the first section by integrating some specific requirements into their games (Fig. 2). Students built a bright field microscope with Köhler illumination and projected their images onto a webcam (optics). Glass and polydimethylsiloxane (PDMS) components comprised the microfluidic chip (microfluidics) and housed the euglena (microbiology). The holder for the chip and euglena-steering LEDs was designed in Solidworks (CAD) and 3-D printed (fabrication). The students constructed a polycarbonate housing for the game controller using a band saw and drill press (fabrication). The students revisited electronic breadboarding and soldering when creating the electronic circuits to communicate between the LEDs, joystick, microcontroller, and computer. Finally, they used MATLAB to program the microcontroller, implement real time image recognition, and provide the user interface for the game experience (image processing and programming).Open in a separate windowFig 2Biotic game-based courses encourage students to integrate a versatile set of relevant STEM topics.Image credits: Taken by N. J. C. (credit for the work and artifacts to the students who took the course).We challenged students to consider the ethical implications [6] of manipulating life in a game context before building their projects. Although phototaxis experiments with euglena are commonplace in education, and have hitherto raised no ethical concerns, the equivalent manipulation in the form of a game warrants its own ethical analysis as provided by Harvey et al. [7]. The students read and discussed this paper, then wrote a 200-word essay on whether they found it permissible or not to make and play biotic games. Students had the choice to switch to a nongame project of equivalent complexity. All students found euglena-based games permissible, pointing out that “they are nonsentient and cannot feel pain,” followed by a diverse range of considerations such as “the euglena are still free to act as they please,” “there needs to be an educational intention,” or “a pet…provides a way…to work on responsibility and caring.” Based on further student-initiated discussions that spontaneously emerged throughout the course, we believe that biotic games are effective in providing a stimulating, student-relevant, in-class context for bioethics.We motivated the game design project to the students as having educational potential at two levels, i.e., learning by building and learning by playing; we lectured them about the needs and opportunities for new approaches to K–12 STEM education [8,9]. The students were then asked to consider building a game that had educational value for the player. Educational value has many aspects, which was reflected in students’ statements regarding their intended educational outcomes for their games on their course project websites. These ranged from more factual learning objectives (“learn about…” “…inner working,” “…structural detail,” “… light responses,” “…euglena behavior”) to objectives affecting attitude (“spark interest,” “generate fascination,” “encourage to explore,” “respect for life”). We also had a game designer give a guest lecture to the students. For pragmatic reasons, we requested the students keep games very simple (ideally having just a single in-game objective) and cap game duration at one minute. Before, during, and after their projects, students received feedback from instructors as well as from their peers on their games from technical and user perspectives.The games that the students ultimately produced were diverse and creative (Fig. 2 and S1 Video), including single and multiplayer scenarios, games where euglena hit virtual targets, and games where euglena pushed virtual objects. Games that involved pushing objects across the screen (relying on collective motion of many organisms) were generally more consistent at correlating player strategy to scored points than those that involved hitting target objects. The quality and robustness of these integrated projects naturally varied, and individual groups placed more or less emphasis on different aspects based on personal preferences and learning goals (for example, fabricating a more elaborate housing for the game controller versus programming more complex game mechanics). A key point was that the students did not rely on prepared materials or platforms to develop their games but rather had to design, build, and test their game setups from scratch, thereby revisiting and deepening the primary learning goals of the course with some freedom to follow their own learning aspirations (Fig. 2). The final project deliverables were a two-minute project demonstration video, a website describing the elements of the project, and a game that all instructors and students played on the final day (Fig. 1B), which led to lots of laughter as well as in-depth discussions on technical details.Many students self-reported that they enjoyed the project and that it led to increased motivation and effort during the course. In response to the question “Do you think you were motivated to try harder or had more fun (and thereby learned more) during your final project because you were making a game (rather than just building a technical instrument, for example)? If so—please give some examples:” 15 out of 17 students responded “Very/definitely” on a five point scale. As examples, students listed: “wanted to make the best game,” “want to make it clever and cool in the eyes of classmates who are play testing,” “motivated during final push,” “willing to put in more time,” “was fun”/”made it fun,” “create a game that actually works,” “reinforced what was learned before,” and “provided room for creativity.” These comments reflect the overall excitement we saw for the biotic game project. While these responses do not constitute rigorous proof regarding course effectiveness (which will require more detailed and controlled assessments in the future), we consider this course a success based on our teaching experiences.45 students have now taken this class over the past three years, with 18 students in our most recent offering. We used each year to iterate and improve our implementation. For example, we changed the organism and stimulus from Paramecia galvanotaxis [5] to Euglena phototaxis, which gave more reliable long-term responses. We also added a simple microfluidics unit enabling students to build more robust organism housing chambers. We changed the microscope structure from LEGO to Thorlabs parts (essentially trading the emphasis on 3-D structural design, flexibility, and cost for a more in-depth focus on high-end optics and their alignment). Finally, we explicitly asked the students to design and fabricate a housing for the game controller to better incorporate fabrication skills like using a band saw and tapping screw threads. So far, we primarily used MATLAB as the programming component given its widespread use in education and research and the available Arduino interface. However, MATLAB is not particularly well-suited to support game design and is also not free, making translation into lower resource settings challenging. For the future, we are considering moving to smartphone-based control (such as Android) given that these mobile environments are very flexible and increasingly used for control of scientific and consumer instruments and are becoming more widespread in education. We also see the opportunity to better emphasize and teach the approach of iterative design; for example, by letting students prototype and test their game ideas on paper [10] and simple programming environments like Scratch [11] first, before attempting the full implementation. It would likely also be very rewarding for the students to be able to take their project home at the end of the course. In summary, many different course design decisions can be made based on specific intended educational outcomes. Not all of these can be fit into one course at the same time, and clear decisions should be made on how to balance covering a breadth of topics with depth on a selected few.As a preliminary test of another age range, time frame, and budget, we taught a greatly simplified 3-hour workshop where high school and middle school students assembled a low-cost microscope and microfluidics chamber, attached it to a smartphone, and stimulated euglena using a preprogrammed Arduino-based controller (see supplements). We had no game interface implemented yet on the phone, but the students could observe the euglena responses to the light stimuli. All students were able to complete the project and take their microscopes home. Over half of our undergraduate student teams also volunteered to present their game projects for this outreach event which took place multiple weeks after their class had ended. This separate experience suggests that the biotic game concept holds promise for reaching a wider age range in a shortened timespan and at a greatly reduced budget, and that completed games can be used in outreach activities. We are currently developing a kit modeled after this unit.In conclusion, we consider biotic games promising in motivating integrated, hands-on learning at the interface of life science and engineering. Our efforts so far indicate that this concept could be adapted to various age groups and learning goals with the potential for wider future impacts on education. We draw upon the analogy to robotics, where microcontrollers went from initially unfathomable as an educational tool to the vision of Papert and collaborators and their use of programmable robotics with children [12], eventually leading to multiple commercial realizations (LEGO mindstorm, Arduino, etc.), a large public following, and a major role in education both in the classroom and through competitions such as First Robotics [1]. We also see additional potential for integrating more creative and artistic aspects into STEM, i.e., leading to generalized Science, Technology, Engineering, Arts, and Mathematics (STEAM) disciplines [13]. We invite others to join us in these endeavors—all instructional materials are available in the appendix for further adaptations and educational use.     

Training load,recovery and game performance in semiprofessional male basketball: influence of individual characteristics and contextual factors

This study examined the effects of individual characteristics and contextual factors on training load, pre-game recovery and game performance in adult male semi-professional basketball. Fourteen players were monitored, across a whole competitive season, with the session-RPE method to calculate weekly training load, and the Total Quality Recovery Scale to obtain pre-game recovery scores. Additionally, game-related statistics were gathered during official games to calculate the Performance Index Rating (PIR). Individual characteristics and contextual factors were grouped using k-means cluster analyses. Separate mixed linear models for repeated measures were performed to evaluate the single and combined (interaction) effects of individual characteristics (playing experience; playing position; playing time) and contextual factors (season phase; recovery cycle; previous game outcome; previous and upcoming opponent level) on weekly training load, pre-game recovery and PIR. Weekly load was higher in guards and medium minute-per-game (MPG) players, and lower for medium-experienced players, before facing high-level opponents, during later season phases and short recovery cycles (all p < 0.05). Pre-game recovery was lower in centers and high-experience players (p < 0.05). Game performance was better in high-MPG players (p < 0.05) and when facing low and medium-level opponents (p < 0.001). Interestingly, players performed better in games when the previous week’s training load was low (p = 0.042). This study suggests that several individual characteristics and contextual factors need to be considered when monitoring training load (playing experience, playing position, playing time, recovery cycle, upcoming opponent level), recovery (playing experience, playing position) and game performance (opponent level, weekly training load, pre-game recovery) in basketball players during the competitive season.     

The Effect of Online Violent Video Games on Levels of Aggression

Background

In recent years the video game industry has surpassed both the music and video industries in sales. Currently violent video games are among the most popular video games played by consumers, most specifically First-Person Shooters (FPS). Technological advancements in game play experience including the ability to play online has accounted for this increase in popularity. Previous research, utilising the General Aggression Model (GAM), has identified that violent video games increase levels of aggression. Little is known, however, as to the effect of playing a violent video game online.

Methods/Principal Findings

Participants (N = 101) were randomly assigned to one of four experimental conditions; neutral video game—offline, neutral video game—online, violent video game—offline and violent video game—online. Following this they completed questionnaires to assess their attitudes towards the game and engaged in a chilli sauce paradigm to measure behavioural aggression. The results identified that participants who played a violent video game exhibited more aggression than those who played a neutral video game. Furthermore, this main effect was not particularly pronounced when the game was played online.

Conclusions/Significance

These findings suggest that both playing violent video games online and offline compared to playing neutral video games increases aggression.     

A dynamic over games drives selfish agents to win–win outcomes

Understanding human institutions, animal cultures and other social systems requires flexible formalisms that describe how their members change them from within. We introduce a framework for modelling how agents change the games they participate in. We contrast this between-game ‘institutional evolution’ with the more familiar within-game ‘behavioural evolution’. We model institutional change by following small numbers of persistent agents as they select and play a changing series of games. Starting from an initial game, a group of agents trace trajectories through game space by navigating to increasingly preferable games until they converge on ‘attractor’ games. Agents use their ‘institutional preferences'' for game features (such as stability, fairness and efficiency) to choose between neighbouring games. We use this framework to pose a pressing question: what kinds of games does institutional evolution select for; what is in the attractors? After computing institutional change trajectories over the two-player space, we find that attractors have disproportionately fair outcomes, even though the agents who produce them are strictly self-interested and indifferent to fairness. This seems to occur because game fairness co-occurs with the self-serving features these agents do actually prefer. We thus present institutional evolution as a mechanism for encouraging the spontaneous emergence of cooperation among small groups of inherently selfish agents, without space, reputation, repetition, or other more familiar mechanisms. Game space trajectories provide a flexible, testable formalism for modelling the interdependencies of behavioural and institutional evolutionary processes, as well as a mechanism for the evolution of cooperation.     

Competition over Personal Resources Favors Contribution to Shared Resources in Human Groups

Members of social groups face a trade-off between investing selfish effort for themselves and investing cooperative effort to produce a shared group resource. Many group resources are shared equitably: they may be intrinsically non-excludable public goods, such as vigilance against predators, or so large that there is little cost to sharing, such as cooperatively hunted big game. However, group members'' personal resources, such as food hunted individually, may be monopolizable. In such cases, an individual may benefit by investing effort in taking others'' personal resources, and in defending one''s own resources against others. We use a game theoretic “tug-of-war” model to predict that when such competition over personal resources is possible, players will contribute more towards a group resource, and also obtain higher payoffs from doing so. We test and find support for these predictions in two laboratory economic games with humans, comparing people''s investment decisions in games with and without the options to compete over personal resources or invest in a group resource. Our results help explain why people cooperatively contribute to group resources, suggest how a tragedy of the commons may be avoided, and highlight unifying features in the evolution of cooperation and competition in human and non-human societies.     

Evolutionary Stability in the Asymmetric Volunteer's Dilemma

It is often assumed that in public goods games, contributors are either strong or weak players and each individual has an equal probability of exhibiting cooperation. It is difficult to explain why the public good is produced by strong individuals in some cooperation systems, and by weak individuals in others. Viewing the asymmetric volunteer''s dilemma game as an evolutionary game, we find that whether the strong or the weak players produce the public good depends on the initial condition (i.e., phenotype or initial strategy of individuals). These different evolutionarily stable strategies (ESS) associated with different initial conditions, can be interpreted as the production modes of public goods of different cooperation systems. A further analysis revealed that the strong player adopts a pure strategy but mixed strategies for the weak players to produce the public good, and that the probability of volunteering by weak players decreases with increasing group size or decreasing cost-benefit ratio. Our model shows that the defection probability of a “strong” player is greater than the “weak” players in the model of Diekmann (1993). This contradicts Selten''s (1980) model that public goods can only be produced by a strong player, is not an evolutionarily stable strategy, and will therefore disappear over evolutionary time. Our public good model with ESS has thus extended previous interpretations that the public good can only be produced by strong players in an asymmetric game.     

Effects of large gatherings on the COVID-19 epidemic: Evidence from professional and college sports

We compare COVID-19 case loads and mortality across counties that hosted more versus fewer NHL hockey games, NBA basketball games, and NCAA basketball games during the early months of 2020, before any large outbreaks were identified. We find that hosting one additional NHL/NBA game in March 2020 leads to an additional 7520 cases and 658 deaths. Similarly, we find that hosting an additional NCAA Division 1 men's basketball game in March 2020 results in an additional 34 deaths. Back-of-the-envelope calculations suggest that the per-game fatality costs were 200–300 times greater than per-game spending.     

Concurrent Bursty Behavior of Social Sensors in Sporting Events

The advent of social media expands our ability to transmit information and connect with others instantly, which enables us to behave as “social sensors.” Here, we studied concurrent bursty behavior of Twitter users during major sporting events to determine their function as social sensors. We show that the degree of concurrent bursts in tweets (posts) and retweets (re-posts) works as a strong indicator of winning or losing a game. More specifically, our simple tweet analysis of Japanese professional baseball games in 2013 revealed that social sensors can immediately react to positive and negative events through bursts of tweets, but that positive events are more likely to induce a subsequent burst of retweets. We confirm that these findings also hold true for tweets related to Major League Baseball games in 2015. Furthermore, we demonstrate active interactions among social sensors by constructing retweet networks during a baseball game. The resulting networks commonly exhibited user clusters depending on the baseball team, with a scale-free connectedness that is indicative of a substantial difference in user popularity as an information source. While previous studies have mainly focused on bursts of tweets as a simple indicator of a real-world event, the temporal correlation between tweets and retweets implies unique aspects of social sensors, offering new insights into human behavior in a highly connected world.     

Adaptive search space pruning in complex strategic problems

People have limited computational resources, yet they make complex strategic decisions over enormous spaces of possibilities. How do people efficiently search spaces with combinatorially branching paths? Here, we study players’ search strategies for a winning move in a “k-in-a-row” game. We find that players use scoring strategies to prune the search space and augment this pruning by a “shutter” heuristic that focuses the search on the paths emanating from their previous move. This strong pruning has its costs—both computational simulations and behavioral data indicate that the shutter size is correlated with players’ blindness to their opponent’s winning moves. However, simulations of the search while varying the shutter size, complexity levels, noise levels, branching factor, and computational limitations indicate that despite its costs, a narrow shutter strategy is the dominant strategy for most of the parameter space. Finally, we show that in the presence of computational limitations, the shutter heuristic enhances the performance of deep learning networks in these end-game scenarios. Together, our findings suggest a novel adaptive heuristic that benefits search in a vast space of possibilities of a strategic game.     

The Hot (Invisible?) Hand: Can Time Sequence Patterns of Success/Failure in Sports Be Modeled as Repeated Random Independent Trials?

The long lasting debate initiated by Gilovich, Vallone and Tversky in is revisited: does a “hot hand” phenomenon exist in sports? Hereby we come back to one of the cases analyzed by the original study, but with a much larger data set: all free throws taken during five regular seasons () of the National Basketball Association (NBA). Evidence supporting the existence of the “hot hand” phenomenon is provided. However, while statistical traces of this phenomenon are observed in the data, an open question still remains: are these non random patterns a result of “success breeds success” and “failure breeds failure” mechanisms or simply “better” and “worse” periods? Although free throws data is not adequate to answer this question in a definite way, we speculate based on it, that the latter is the dominant cause behind the appearance of the “hot hand” phenomenon in the data.     

Short and Long Term Investor Synchronization Caused by Decoupling

The dynamics of collective decision making is not yet well understood. Its practical relevance however can be of utmost importance, as experienced by people who lost their fortunes in turbulent moments of financial markets. In this paper we show how spontaneous collective “moods” or “biases” emerge dynamically among human participants playing a trading game in a simple model of the stock market. Applying theory and computer simulations to the experimental data generated by humans, we are able to predict the onset of such moments before they actually happen.