This is probably true. There are things definitely less conscious than us. It'll be interesting if it is possible for us to comprehend higher consciousness or if its like a never ending race to the top. Creatures so intelligent they are just beyond our comprehension.
Intuitively we can postulate the humans are more conscientious than a chicken, and the chicken is more conscientious than a bacteria, and the bacteria (maybe it can "feel" pain) is more conscientious than the thermostat (who probably is not conscientious in any way). But conscience is not really measurable, so, we can't be really sure if a rock is more conscientious than us, or than a fellow human is conscientious at all (p-zombies).
Who says? We used to could.not measure light precisely, only vague notions of color. Maybe we are just in a similar state.