Dancer one is clever, trick is in not focusing on the entire silhuette, as that way she will spin for you only in one direction and you just can't imagine it changing direction, since she's clearly spinning in constant motion and you can see her stretched leg clearly going lower in front of the other (meaning it spins clockwise for me btw). Focus on her feet or shadow and imagine it changing direction (constant jerking of the gif helps) - suddenly she spins the other way, lifting her leg up as she spins.