There's actually objective tests you can perform with people with agnosia, example: http://m.nautil.us/issue/47/consciousness/we-need-conscious-robots http://m

There's actually objective tests you can perform with people with agnosia, example: http://m.nautil.us/issue/47/consciousness/we-need-conscious-robots http://m.nautil.us/issue/47/consciousness/we-need-conscious-... > In fact, even our sensation of the present moment is a construct of the conscious mind. We see evidence for this in various experiments and case studies. Patients with agnosia who have damage to object-recognition parts of the visual cortex can’t name an object they see, but can grab it. If given an envelope, they know to orient their hand to insert it through a mail slot. But patients cannot perform the reaching task if experimenters introduce a time delay between showing the object and cueing the test subject to reach for it. Evidently, consciousness is related not to sophisticated information processing per se; as long as a stimulus immediately triggers an action, we don’t need consciousness. It comes into play when we need to maintain sensory information over a few seconds.