 Bigfin reef squids exhibit strong positive phototactic behaviour ( attraction to light ) and will move readily within a certain distance of a light source . Studies have proposed that this might be an involuntary stimulus behaviour , as the squids immediately stop all other movements once a light source is switched on . The colour of the light does not matter , but it has been shown that they react more strongly to underwater lights between the intensities of 1 @.@ 5 to 2 @.@ 5 lx , with peak ranges of 2 @.@ 5 to 10 @.@ 0 lx . 
