From the late 1920s, Dalí progressively introduced many bizarre or incongruous images into his work which invite symbolic interpretation. While some of these images suggest a straightforward sexual or Freudian interpretation (Dalí read Freud in the 1920s) others (such as locusts, rotting donkeys, and sea urchins) are idiosyncratic and have been variously interpreted. Some commentators have cautioned that Dalí’s own comments on these images are not always reliable.