<h1>Optical Illusion</h1><a class='_ac _lb' lightbox='http://www.niehs.nih.gov/kids/illusion/images/illus10.jpg '><img class='_ac _di img-fluid' style='width:583px; height:inherit; background: inherit;' data-delaysrc='http://www.niehs.nih.gov/kids/illusion/images/illus10.jpg' src='http://www.niehs.nih.gov/kids/illusion/images/illus10.jpg' /></a><br/>How many human faces can you find in this picture?<br/>There are probably more than you first see, so keep trying.<br/>How did you do?<br/><br/>Answer Seeing 4 or 5 is average; 6 or 7, above average; 8 or 9, very observant; 10 or 11, extraordinarily observant.