Kittens that are, between their third week and their third month of life, kept in a room lined only with horizontal stripes will, as adults, have no trouble romping from table to floor, but they will bump into table and chair legs. They behave throughout their lives as if vertical objects do not exist.
White-crowned sparrow chicks must hear their species’ song between their tenth and fiftieth day of life. It is only during this critical period of time that they can tape and store the parental songs in their brain — and so be able to reproduce the song later in life.
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