Rats' memory for time and relational responding in the duration-comparison procedure

► Rats decided if a comparison (c) was 1.2-s shorter or longer than a standard (s). ► First study to show that rats can acquire a relational duration discrimination. ► On equal-duration test trials, c was judged longer than s as the s-c delay increased. ► This result is consistent with subjective shortening of the s duration. ► Transfer tests indicated a mixture of absolute and relational response strategies.