Swap the photo you picked as more attractive, and most people won't notice

Petter Johansson and colleagues showed participants two faces and asked them to point to the more attractive one, then handed over that photo using a sleight-of-hand card trick that secretly swapped it for the rejected face. Most participants didn't detect the switch, and many confidently explained why they'd 'chosen' a face they'd actually rejected.

— Petter Johansson, Lars Hall, Betty Sikström, Andreas Olsson, Failure to Detect Mismatches Between Intention and Outcome in a Simple Decision Task — Science, 2005