Arrange your fingers like the image below, and then look at them closely.
From Bertamini (2019) i-Perception
Do you notice anything odd?
Psychologist Marco Bertamini of the University of Liverpool describes this test in a fun new paper. According to Bertamini, seven of the ten people he surveyed reported that their little fingers clearly appeared to be ‘too far away’, to the extent that they did not appear to be part of their hands.
Bertamini suggests that the illusion is caused by