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VISION 



Figure 1 Schematic of conditioning pool divided by sheets of 

 black Plexiglas into maintenance pens (MP) and a modified-Y 

 maze. The 3-ft-high pool was filled to a depth of 20 in. and was 

 shaded by a 6-ft-high tarp roof. The target doors (lower right) 

 were built of transparent Plexiglas with mountings to hold inter- 

 changeable square targets. 



standard piece of thawed mackerel. Care was taken to prevent any olfactory 

 cues from biasing the shark's response tendencies by presenting the fish 

 reward impaled on a stiff wire only after the shark had entered the goal area. 

 If a subject did not choose the correct target within 60 s after beginning a 

 trial, it was guided through the correct door, but an error was recorded. The 

 discriminations were considered learned (p < 0.01) when the shark made at 

 least seventeen correct responses over three consecutive days (Bogartz 1965). 

 The sharks were trained first on a black-vs-white discrimination and then 

 on a horizontal-vs-vertical pattern discrimination in which each 30.4-cm 2 

 target was painted with three black and three white 2-in-wide stripes. Each 

 of these striped targets served as correct or incorrect an equal number of 



