Experiment - Rubber Pencil

I conducted the "Rubber Pencil" experiment. This experiment was conducted on a Mac laptop. I noticed that when I waved the pencil vertically, it would seem to be heavy, or appear to be dominant on the left side than the right. Almost as if the pencil was real on the left side and a reflection on the right. When the experiment was performed horizontally, the result was not as noticeable as when performed vertically. It was observed though it was more pronounced when lowered, than raised high.