I can't seem to find anything in the rule book for how to do perception checks for the Palladium systems (Palladium Fantasy RPG, Rifts, Dead Reign, etc). How do you do them? Is there a base attribute that can provide bonuses for this?
The obvious base attribute is intelligence.
I'd recommend adopting the system used for stat check in Basic Role Playing (aka BRP, Chaosium's house system), especially given Palladium does not conform to the 3d6 for all stats.
Perception is IQ x 5 as a percentage. If you want to make something harder to perceive drop the 5 to a lower number. If they are trying to perceive a person hiding have both roll and the highest successful value succeeds. So someone with hide of 40% versus someone with an IQ of 12 (60% perception) could see the following:
Roll of 30 vs roll of 20: both succeed but the character is not seen. Roll of 40 vs roll of 41: both succeed but the character is seen...this shows and advantage of the system, higher skill gives you a better chance to beat the lower skill if both succeed.
Perception is covered in Palladium in 2 other products- Dead Reign and Rifts Unlimited Edition, page 367. To sum:
Roll on D20-
Perception & Skills: Skills such as Prowl, Concealment, etc add to Perception. + 1 every 10 points of skill. Use common sense… prowl does not help in discovering a secret door.
Bonuses are from ME or IQ, depending on GM's preference- most use ME with the save vs. Psionics progression table.
cmcculloh adds some more Palladium references - Beyond the Supernatural, page 170:
There are several methods you can use or adopt:
Key things to remember are that there are specific detection skills representing training for finding certain things (such as secret doors), and there are specific skills for stealth. Stealth-related skills, when rolled indicate success or failure and do not invite an opposed roll or other contest between two or more characters for detection.