When the tantalizing scent of chocolate chip cookies wafts by, how does your mind know what it means? Nobel laureate Richard Axel will explain in his talk, “Scents and Sensibility: Representations of the Olfactory World in the Brain,” in Cornell’s annual Ef Racker Lecture in Biology and Medicine Thursday, Nov. 15, at 8 p.m. in Call Alumni Auditorium, Kennedy Hall. A reception will follow in Kennedy Atrium. The talk is free and open to the public.