Editing M&M Revised (v1.5) System Resource Document (section)

===HOW SKILLS WORK===
When you use a skill, make a skill check to see how you do. Based on the
circumstances, your result must match or beat a particular number to use
the skill successfully. The harder the task, the higher the number you need
to roll. (See Checks, page 9, for more information.)
UNTRAINED SKILL CHECKS
Generally, if you attempt a task requiring a skill you don’t have, you make
a skill check as normal. Your skill modifier doesn’t have a skill rank added
in because you don’t have any ranks in the skill. You do get other modifiers,
though, such as the ability modifier for the skill’s key ability.
Many skills can only be used if you are trained in the skill. Skills that
cannot be used untrained are marked with a “No” in the “Untrained” column
on the Skills table and listed as “Trained Only” in their descriptions.
Attempts to use these skills untrained automatically fail.
INTERACTION SKILLS
Certain skills, called interaction skills, are aimed at dealing with others
through social interaction. Interaction skills allow you to influence
the attitudes of others and get them to cooperate with you in one way
or another. Since interaction skills are intended for dealing with others
socially, they have certain requirements.
First, you must be able to interact with the subjects of the skill. The
subjects must be aware of you and able to understand you. If you don’t
speak the same language, or they can’t hear you for some reason, that’s
the same as working without the proper tools, a –4 on your skill check.
Interaction skills work best on intelligent subjects, ones with an Int
score of 3 or better. You can use them on creatures with Int 1-2, but with
a –8 penalty; they’re just too dumb to get the subtleties of your point. You
can’t use interaction skills at all on subjects lacking one or more mental
ability scores. (Try convincing a rock to be your friend—or to be afraid of
you—sometime.) The Immunity power (see page 89) can also render some
characters immune to interaction skills.
You can use interaction skills on groups of subjects at once, but only to
achieve the same result for all. So you can attempt to use Bluff or Diplomacy to
convince a group of something, or Intimidate to cow a crowd, for example, but
you can’t try to convince some individuals of one thing and the rest of another,
or to intimidate some people and not others. The GM decides if a particular
use of an interaction skill is effective against a group, and may apply modifiers
depending on the situation. The general rules for interaction still apply: everyone
in the group must be able to hear and understand you, for example, or you
suffer a –4 on your skill check against them. Mindless subjects are unaffected.