Fallout Shelter – Determining SPECIAL Inheritance in Children

Mating: Bring a male and a female Dweller together into the living quarters. In larger living quarters you can bring in more Dwellers and let them work it out. The higher the Charisma the faster they will mate.

Direct offsprings will not mate, the game prevents incestuous behavior. If you do not keep log of your bloodlines (which you most probably don't) there are two ways to detect blood relationship:

1. By default new borns will get the last name of the father. So if two dwellers have the same last name, they might be related.
2. In case related dwellers are in the living quarters, they will bring up the topic that it is nice to meet with the family.

Pregnancy: While women are pregnant they can work. But they will not take care of any incidents but run into the living quarters instead. Make sure to assign at least one male/non-pregnant Dweller to all stations and don't equip pregnant women with weapons since they don't use them.

Deliver Baby: After mating it takes 3 hours for a baby to be born. You do not have to be in the game for this whole time. Just come back after 3 hours and you'll have a baby.

Make sure to have enough room in your living quarters. If your vault is full, women will simply stay pregnant until there is free room. There won't be an indicator and neither the pregnant dwellers will complain in any way. (Also see maximum population below)

Growing up: It takes another 3 hours until children are fully grown up. In their stats they have a grow-up-bar. During this time they can not be assigned to jobs. Again you do not have to be in the game during this time.

Overpopulation: Take care to not grow too fast. Once a baby is born you will need to feed it. Since children won't work you quickly run out of resources and have to juggle your workforce between your water treatment plants and diners if you get too many babies at once.

Maximum Population: The maximum number of dwellers in the vault is 200 - if you reach 200 dwellers, you have to be very careful placing men and women together in living quarters, or you'll have a whole lot of perpetually-pregnant females.

Do note that nothing has been made official, and this is a compilation of observations/hypotheses.

Strength

• Vault:
  • Decreased timer while working in power plants
• Wastes:
  • Needed to pry open lockers and boxes.
  • May also affect damage done by guns.
  • May increase a Dwellers capacity.

Perception

• Vault:
  • Hit chance in combat
  • Decreases water production timer of the Water Treatment and Water Purification rooms
• Wastes:
  • Find stuff like abandoned buildings
  • Critical attack cross hairs expand and contract slower, making it easier to deal maximum damage (×5) with a critical attack.

Endurance

• General:
  • Health points gained on level up (does not increase hp retroactively, max out endurance to 10+7 outfit and then start leveling to get maximum health)
  • Resist radiation and damage (11 Endurance = immune to radiation)
• Vault:
  • Food and water production timers of the Nuka-Cola bottler room.

Charisma

• Vault:
  • Improved fertility. (Reduced time to get pregnant.)
  • Decreases production timer in Radio room.
• Wastes:
  • Also chance of befriending people in the wastes (Gives the xp but no damage taken)
  • Interaction with groups of slaves

Intelligence

• Vault:
  • Med-bay (Stims and Radaway) production timers
• Wastes
  • Heal/help people

UPDATE:

• Vault/Wastelands:
  • also increases Exp gain (for level and Special stat increasing), extinguishing fire

Agility

• Vault:
  • Food production timer of the Diner and Garden rooms.
  • Increases attack speed.
• Wastes:
  • Run away from unwinnable fights taking less damage

Luck

• Vault:
  • Decreases chance of rush failure.
  • Increases amount of caps earned when resources collected from a production room (also increases chance to earn those caps)
  • Increases critical bar fill up rate.
• Wastes
  • Amount of loot found outside vault

Further reading and sources:

• Reddit: /r/foshelter What does each attribute do?
• Reddit: /r/foshelter Guys, power armor doesn't give any defensive stats in the wastes. ...
• Loading screen tips from Fallout Shelter for iOS

Tip:

• I set my shelter that way, to have the medbay spread in the vault to handle fire faster.
• the difference in having 1 or 2 intelligence is that a dweller with 2 intelligence levels up in half the time
• queuing my new matured dwellers to go to school so they get intelligence 2 or 3 then endurance for max HP and after that their main stat - super efficient

UPDATE: If you want to nerd out on more specifics, I recommend Section 7 of this Fallout Shelter Efficiency Data.

Also, here someone suggests that skills above 10 continue to benefit the dweller/explorer:

• Room efficiency data thread on Reddit