| intuitive(adjective, passionate, violent, abrupt, instinctive) |
| knee-jerk(adjective, natural, instinctive, unwilling, automatic) |
| mechanical(adjective, natural, instinctive, automatic, inherent) |
| native(adjective, natural, instinctive, automatic, inherent) |
| normal(adjective, natural, instinctive, automatic, inherent) |
| regular(adjective, natural, instinctive, automatic, inherent) |
| rooted(adjective, natural, instinctive, automatic, inherent) |
| second-nature(adjective, instinctive, automatic, innate, inherent) |
| typical(adjective, natural, instinctive, automatic, inherent) |
| unlearned(adjective, natural, instinctive, automatic, inherent) |
| automatic(adjective, simple, violent, natural, casual) |
| instinctual(adjective, natural, instinctive, unwilling, automatic) |
| unasked(adjective, natural, spontaneous, freely, voluntary) |
| informal |
| unbidden(adjective, simple, natural, casual, impulsive) |
| unconscious(adjective, simple, natural, casual, impulsive) |
| unguided(adjective, impulse) |
| unplanned(adjective, simple, natural, casual, impulsive) |
| unpretentious |
| unrehearsed(plain, impulsive, spur-of-the-moment) |