title: Safe periods both explain and need explaining.
authors.affiliation: msidman@aol.com
authors.forename: M
authors.initials: M
authors.lastname: Sidman
mesh_terms: D000818:Animals; D001070:Appetitive Behavior; D001362:Avoidance Learning; D004597:Electroshock; D006801:Humans; D009042:Motivation; D012055:Reinforcement Schedule