What can an octopus see that a vertebrate ca n't due to the blind spot in vertebrate -LRB- including human -RRB- eyes where octopuses have no blind spot ?
`` Where is the best place to hide a small recording device in a person 's backpack -LRB- bag -RRB- so as not to be found ? How ? E.g. at the top-back or mid-back-side ? Is there a '' `` blind spot '' '' in a bag that people do n't tend to see or feel ? ''