That is, instinctively and without being aware of it happening. Human male pheromones are given off at quite minute levels so that it is not obvious to a woman recipient why she is suddenly attracted to a man. Yet it is the scent messages of the pheromone which drive her to become attracted. This is because the part of the brain which processes the pheromone by-passes the conscious awareness. To understand how this can happen we must first understand how scents interact with the brain.
Scents are highly volatile molecules which detach themselves from their source and float in the air.
When a pheromone recipient comes within range, the scent molecules of the pheromone rush through the nostrils, over spongy tissue inside the nose which humidifies the air in order to make the scent molecule more focused, and then reach up two narrow chambers, where, just at the entrance to the brain behind the bridge of the nose, those molecules land on the special glands about the size of shirt buttons. There, molecules are translated into electrical signals. Just like your voice is converted into an electrical signal in the telephone so that it can be sent along a wire. The scent signal is then transmitted to the processing part of the brain which sorts the scent into categories. A smell of meat cooking on a barbecue may trigger the desire to eat, for example.