Array#map
returns a new array. You have to assign it to the variable:
personality_types = ["bad", "good", "great"]
personality_types = personality_types.map { |type| "#{type} person" }
Or use Array#map!
to directly change the array:
personality_types = ["bad", "good", "great"]
personality_types.map! { |type| "#{type} person" }
personality_types
#=> ["bad person", "good person", "great person"]