Pfungst then examined the behaviour of the questioner in detail, and showed that as the horse's taps approached the right answer, the questioner's posture and facial expression changed in ways that were consistent with an increase in tension, which was released when the horse made the final, correct tap. This provided a cue that the horse could use to tell it to stop tapping. The social communication systems of horses may depend on the detection of small postural changes, and this would explain why Hans so easily picked up on the cues given by von Osten, even if these cues were subconscious.