Bonuses may temporarily increase dice pools, and usually represent beneficial circumstances (e.g. a character may have a powerful computer to aid her in a database search) or some special effort on the character's part (an effort of will, a strong desire to succeed, or even a supernatural power).
They also provide players with a physical representation for the modifiers, as real, concrete dice are added to the pool (or taken away from it).
West End Games's Ghostbusters role-playing game by Greg Stafford, Lynn Willis, and Sandy Petersen featured a d6 system with an additive dice pool that was applied to both characteristics and skills.
Shadowrun (1989), designed by Bob Charrette, Paul Hume, and Tom Dowd, used a comparative dice pool, in which players roll a set of six-sided dice and each die rolled was compared to a target number to determine if that die was a success or a failure, with the number of successes determining the outcome of the action taken.
[citation needed] Dowd refined the dice pool system for White Wolf Publishing's Vampire: The Masquerade (1991).
[3]: 123 Vampire: The Masquerade and Over the Edge (1992) were written by Ars Magica designers Mark Rein-Hagen and Jonathan Tweet respectively, the pair having been impressed by the potential of the dice pool mechanic and each having decided to make their own game based on dice pools.
The majority of White Wolf Publishing's subsequent games use variations on Vampire's Storyteller System and use its dice pool mechanic.