To use the ready action distract Spellcasters, it is stated the individual must ready an action once a caster starts casting a spell.
The questions, wouldn't you need at least one point in spellcraft/knowledge arcana to identify a spell is being cast for the readied action to trigger? (Why/Why not)
The situation is that a character wouldn't know a spell is being cast based on loud speaking, a movement of a hand, or an component. Individually perhaps they could be used as readied actions. For example, attack anyone reaching into a small pouch... (because it needs to be specific)
Core Rulebook wrote:
You can ready an attack against a spellcaster with the trigger "if she starts casting a spell." If you damage the spellcaster, she may lose the spell she was trying to cast (as determined by her Spellcraft check result).
So, if the only mechanic for identifying a spell is using spellcraft/knowledge arcana, then a check has to be made for "starts casting a spell" to trigger.
I think people in this world encounter magic often and should not have to make the check. Especially when a person in the back, wearing robes, chanting and pointing at things is ready to unleash chaos. Selecting specific actions such as, if the caster moves their hands seems to neglect other casting potential.