Idiot Savant

Idiot Savant is a perk in Fallout 4.

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

When the perk activates, you will see a laughing Vault-Boy above the compass, and hear a laughing sound. The experience you would have 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 and the probability of it triggering is currently unknown. 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, it is worth comparing the returns you get. 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 is mentally challenged due to neurological disorders or brain injuries, but displays exceptional skill in a specific field such as art, arithmetic, music, or memory, far beyond what most neurotypical people can accomplish, such as recalling specific dates and times or re-playing a piece of music perfectly on piano after hearing it only once.

Bugs

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

Савант