Idiot Savant

Idiot Savant is a perk in Fallout 4.

Effects
Increased chance to receive XP bonuses, but only with low Intelligence.

Ranks
For ranks 1 and 2, the perk randomly activates whenever one gains experience from any source. At 1 Intelligence, the chance of activation is 11%, and one loses 1% per added point of Intelligence. The chance minimizes at 1% at Intelligence 11 or higher.

When the perk activates, a laughing Vault-Boy appears above the compass, and one of several possible laughing sounds are heard. The experience that would have been earned will instead be boosted to 3x (for rank 1) or 5x (for rank 2+). This boost is multiplicative with any normally additive experience bonuses from being Well Rested or having a high Intelligence.

The probability for the "kill bonus" from rank 3 appears to be independent of the bonus experience from rank 1 and 2. The effect lasts 60 seconds.

Comparison to Intelligence

 * $$IntMulti = 1 + (Intelligence \times 0.03)$$


 * $$AvgIdiotSavantExpMulti = 1 + \Bigg(\frac{min(2,IdiotSavantPerkLevel) \times %Chance}{50}\Bigg) $$


 * $$OverallExp = IntMulti \times AvgIdiotSavantExpMulti$$

When comparing a perk point to put into higher Intelligence or Idiot Savant, one can compare benefits above. Each point in Intelligence improves experience gain by 3%. Consulting the above table, it can be seen that with two levels of this perk, average experience gain is optimized at 2 INT and actually drops with each additional Intelligence point until very high levels of Intelligence (15+).

Behind the scenes
The term "idiot savant" is an obsolete term in psychology for Savant syndrome, where a person with neurological disorders or brain injuries displays exceptional skill in a specific field.

Bugs
If the Idiot Savant perk activates when turning in a quest, one will sometimes not get the 3x or 5x multiple of experience points.