A Note on Skills
The fifth edition of the Call of Chthulhu rules does not call for differentiated Skill Checks, so all uncontested tasks are equally difficult and it is only the character’s skill that comes into question. A Dream of Japan alters this notion by listing skill challenges in which the task attempted might be more difficult than another. This can be used to differentiate, for example, Tilda Smith-Chadwick’s chances of successfully driving her Aston Martin at 90 mph while handcuffed versus her chances of cruising Central Park on a Sunday.
When Skill Checks are listed in the text, they will occasionally be followed by a percentile figure, for example, Fast Talk (-50%). In this case the investigator would reduce his chance of success by 50% … and may have to resort to telling the truth! In some circumstances the skill is followed by a bonus – for example, Natural History (+15%). In this instance the character would increase his effective skill by 15%, increasing his odds of success.
In some circumstances, a skill may be elevated above 100% or reduced below 0%. If the Skill Check is important to the game, the investigator should still make the attempt, given that rolls of 0% or 100% are always a success or failure, retrospectively.