Ants and Grass
"Indeed, there's no wind," Grisha licked her finger before pointing it in the air, trying to feel any sensation of moving air, shuddering as she looked at the grass, "Why are they swaying like there's a wind here?"
"Hmm," Compass Carburettor took out a kerchief from his pocket, rolled it into a ball and threw it onto the lawn, observing if anything happened to it. After all, he didn't receive any Mental Energy from the grass.
That was normal, since only organisms capable of sentient thoughts generated any Mental Energy. Those that simply act based on sensory pulses through their nerve synapses didn't have any cognitive thoughts. And hence, they never generated any Mental Energy.
Plants were the best example of this.