My reaction to int scores...
1 The creature will only react to things it experienced in the last round in an "intelligent" fashion. IE most vermin
2 The creatures thoughts are in terms of one word "ideas" - food, hurt, kill, run, pain, ect...
3 Creature can comprehend - to the extent of an individual significantly impaired - language.
4-5 Impaired in terms of thoughtful reasoning process.
If the creature has a wisdom of 15 to 18 and an int of about 4-6... I think of the character "Forrest Gump". One's Brains does not necessarily equal its reasoning capacity. I specifically use the "Vietnam War" scene in that movie as a classic example of how such a charater will reason out situations - even in the heat of battle. The irony of the situation - is that it was BECAUSE that character did not think about his own saftey or how rational his actions were - and got a bit lucky, that they were considered a hero...
6-7 Noticeably below average
8-9 Slightly below the norm. Unable to "get" the concepts of magic.
10-11 Average
12-13 Slightly above the norm
14-15 Noticeably above the norm
16-17 Gifted
18-19 Exceptional
20 + Geinus type intelligence
To put "Einstein" into 3e D and D terms - I would say he would have an effective "intelligence" of 25...