Uniqueness as an artifact caused by limits on current knowledge is a salient point. To give an idea of the state of the art in the understanding of living brains, this page presents a pie chart of known neuron types by species:
However, if they had a moral code like ours they might instead surmise that rats, mice, and flies are viewed as expendable to the actual "rulers" of the planet and that these have an aversion to slicing themselves up for science. So they might conclude the rulers to be one of the primates given the existence of three close species: human/chimp/baboon in one family (monkey).