Game Background and Data

3.2.1. Game Play

We study intrinsic motivation using data collected from Wordsplay.com, a free online im- plementation of the word-hunting game Boggle. Each round of play (a “game”) features a randomly generated grid of letters (see10) and lasts for three minutes. Players score points by finding words in sequences of adjoining letters where no letter is used more than once in a given word and consecutive letters in the word must be adjacent on the game board. The number of points awarded for each word is a non-linear increasing function of the length of the word.

Players have the option to join a team, which will be scored and ranked alongside the individual players. At the end of a round, each player and team receives a final score for the game equal to the cumulative total of points scored for each word that was found. The same word found by two or more players on a team cannot be counted more than once towards

the final score for the team, though the word does contribute for the individual players’ scores. Players and teams are then ranked together so that for each game, an individual is able to determine the number of points scored, the fraction of total possible points scored, his or her individual ranking, and the ranking of his or her team (conditional on being part of a team). The winner for a game is the player or team with the highest final score (number one ranking). Once a round is complete, players must wait an additional 30 seconds before the next round begins with a new random game board.

3.2.2. Data

Our data provides player-game level information for all games played on Wordsplay.com in 2009. For each observation, the data includes game-specific information on all possible words and possible points for the associated game board as well as player-specific information on the actual points scored by the player and the points scored by the players team (conditional on being on a team). Games are indexed by a timestamp for when the round was played. The data allow us to link games over time for a given individual using a unique identifier that must be created by individuals in order to play. Similarly, a unique team identifier allows us to link players in the same team.

Table 32 presents summary statistics for the 24,433 players in our sample. Players play on average 454 games over the course of our sample period; however, as Figure 11 shows, this distribution is highly skewed with the median number of games played being 16. The distribution of the number of games played also differs by whether the player is participating on a team during the given round with the mean and median number of games played as part of a team far lower than when played individually. This difference is driven primarily by the large fraction of players who never play on a team (i.e. play zero games as part of a team). The degree to which players participate on a team is in general quite stark with over 82 percent of players either never playing on a team or always playing on a team during our sample period.

Because we are able to link observations across time for players, we can observe not only features of a particular game but also a players pattern of play over time. We define a spell as a sequence of consecutive games where a score appears for that game. As Figure 12

shows, the distribution of the number of spells played over the course of our sample period is highly skewed. While the mean number of spells is quite large at 89, the median is 4 spells. The mean length of a spell for players is five games with on average 1.2 days between spells. The distribution of spell lengths and distribution of days between spells are shown in Figures13 and 14.

Players score on average 30 points in a game or roughly eight percent of possible points that can be scored. Games vary widely in the number of possible points available so that the variance in the share of possible points scored is far greater than the variance in the absolute number of points scored. Figures 15 and 16 show the distribution of points in the first game every played by a player in our sample period and the distribution of points scored in all games, respectively. Comparing across the two distributions, the number of points players score changes as they play additional rounds. Specifically, the distribution of points scored shifts to the right suggesting that player performance increases on average after the first round of play. Section 4.3 discusses the extent to which we observe evidence of learning across rounds of play.

Table33presents team-level summary statistics on the number of games played and points scored. Because not all individuals play on teams or on the same team during the entire sample period, the number of games played by teams is on average smaller than the number of games played by individual players. The mean number of points and share of possible points scored in a game are higher for teams than for individual players, however, reflecting the fact that teams scores are always weakly better than the scores of the teams individual players.