The habitual route of the betta.
"The habitual route of the betta. When a divider is installed in the tank of a tropical betta, and the fish is lured around the divider with food, subsequently it will make that route its habitual one. As shown in the illustration, even when food is placed in the area of the arrow, instead of taking the quicker route that is directly in front of him, the fish will reach the food by going around the divider."
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from "Another scale of Architecture", Junya Ishigami