Five groups of pigeons were trained in a symbolic choice-matching task involving short (2 s) and long (10 s) durations of houselight as samples. Four groups also received training with a second set of samples: line orientations or 2- and 10-s presentations of keylight. The type of sample-to- comparison mapping varied across groups. Although only two of the five groups demonstrated a choose-short effect (a tendency to choose the comparison associated with a short sample at longer delays), all groups demonstrated temporal summation (a tendency to respond on the basis of the combined duration of two successively presented samples). Moreover, the magnitude of temporal summation was equivalent in groups which did and did not demonstrate a choose-short effect. The results suggest that the processes underlying the perception of sample duration remain invariant across different sample-to- comparison mapping arrangements, but that the memory code used to retain temporal information varies.