If yes, then here's a challenge for you! This is an optical illusion that has been created to make you observe concealed details in a second. Can you spot the heart in this picture of a swan in 3 ...

For the experiment, they chose “The Swan,” by French composer Camille Saint-Saëns, and “Arpa de Oro,” by Mexican composer Abundio Martínez. By attaching external heart rate monitors ...