That's not categorically true. Although a placebo inherently relies on a patient's subjective understanding of receiving a treatment, that understanding can change any number of very objective outcomes. That's why so many studies that measure objective metrics use placebos to begin with.
a good point, and one that highlights the fact that people are unironically relying on "objective"/"subjective" distinctions in this thread - when this division is not necessarily a straightforward one in neurology or philosophy/language. putting a neurological implant in someone's brain doesn't strike me as an act that immediately clarifies this issue, to put it mildly. but this technology is still in its infancy. thus, the more people to "review" it, the better... doesn't mean the benefits they are giving people or the work has to stop... it just doesn't mean some skepticism isn't warranted either...
