You can set your primary attributes however you like during character creation, but the total of these attributes cannot exceed 12 during character creation. All attributes can increase or decrease during gameplay (except intelligence) based on your activities in game.
Strength is the physical power of a person, typically measured by how much you can push, pull or lift a physical object.
Creation Value: 1-5
Max Value: 8
Raised by: proper protein intake (animal meat, etc.), executing actions under a load (like carrying a pack full of rocks while walking around).
Lowered by: protein deficiency, loss of muscle mass
Influences: carry weight, melee damage, calorie burning
Brawling
Melee Weapons
Archery
Rifles
Handguns
Constitution or body type defines everything connected with physical endurance and stamina.
Creation Value: 1-5
Max Value: 5
Raised by: moving in general, walking, running, swimming, etc.
Lowered by: not moving, staying still for longer periods of time
Influences: health points, stamina, damage and status (shock, poison, etc.) resistances, immune system, calorie and water consumption efficiency
Running
Endurance
Dexterity determines how skillful you are in performing everyday and/or complicated actions.
Creation Value: 1-5
Max Value: 5
Raised by: calorie deficiency (losing weight)
Lowered by: calorie sufficiency (gaining weight)
Influences: movement speed and action speed including crafting, eating, reloading.
Thievery
Driving
Demolition
Throwing
Motorcycling
Stealth
Piloting
Intelligence is the capability of perception and successfully performing tasks. Currently, it can not be raised nor lowered by in-game activity.
Creation Value: 1-5
Max Value: 5 (again, currently will not increase by in-game activity)
Influences: squad size limit (if you are the leader)
Awareness
Camouflage
Engineering
Sniping
Survival
Medical