Instinctual Skills are competencies that a character would have from birth simply due to being born the way they are. Although that these skills will be impacted by nurture, the fact that the character can use them at all is caused by nature. Examples of such skills are being able to hear, or see or a birds ability to fly or sleep.
Core to the category of instinctual skills are the five sensory competencies. Even though that almost all characters will have these skills, it does not mean that these skills cannot be improved upon by training. Each sensory competency can be improved by pushing the limits of what the character can already do, such as seeing subtle differences between two objects or attempting to overhear a conversation that is almost outside hearing range. Instinctual skills utilize BQ by default, but there are circumstances that the GM could rule a different trait to be used. An example of such a situation would be trying to hear a person speak through gunfire, which would require MQ rather than BQ, reading a person's handwriting would involve IQ rather than BQ whereas attempting to figure out if a person is lying by touch would involve EQ.
Sight: The character's vision. More ranks in sight denote a keener power of observation rather than an actual improvement in eyesight. An accountant with shortsightedness can still spot an error in tax reporting due to higher observation, but would not be able to see the sniper aiming at him 200 meters away due to the limit of his eyesight. A Nephalem with shifted eyes, would be able to see a faraway target easily; as easily as an airborne eagle sees a running rabbit. However, just as mentioned, he might still be distracted or oblivious to the fact that his fuel gauge is running low.
Touch: The sense of touch of a character. With training, any person could become attuned to their sense of touch. A blind man is able to interpret braille by touch due to sharpened senses which is represented by higher ranks in the touch competency.
Hearing: The sense of hearing. Increased ranks in hearing mean that a character can hear tonal differences, such as being able to interpret musical notes. Almost all Incarnate Adepts can hear into the ultrasonic and subsonic ranges where normal humans can't but that does not mean their hearing competency is higher, if they can't discern sounds well.
Taste: The sense of taste. Increased ranks can benefit a character who can differentiate and identify tastes. Characters that work in the hospitality industry, such as a wine sommelier or a chef-cook will most likely have ranks in this skill.
Smell: Olfactory ability. Each higher rank in smell can allow characters to pick up a scent among others or identify smells better. Anubians have canine DNA and have incredible sense of smell and could pick out a man in a crowd just by his odour.