A medicament for promoting memory consolidation, which comprises, as an active ingredient, a non-natural retinoid, preferably a retinoid having a basic skeleton comprising an aromatic ring bound with an aromatic carboxylic acid or tropolone by means of a bridging group, more preferably 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthaleny)carbamoyl]benzoic acid or 4- [(3,5-bis-trimethylsilylphenyl)-carboxamido]benzoic acid.