Wang, S.; Li, J. W. J.; Ma, C.; Poon, E. S. K.; Sin, S. Y. W.

Long-term memory has been extensively documented in many animals across a range of ecological contexts. Far less is understood, however, about how long memories persist after active modification or how conflicting memories are adaptively regulated to enable flexible behaviour. Parrots are widely recognized for their high intelligence and cognitive capability, yet the study of memory has focused on only a handful of large parrot species. Here, using a binary choice symbolic system, we conducted three experiments on 28 rosy-faced lovebirds (Agapornis roseicollis) to investigate (1) memory retention of initial associative learning at intervals of two weeks, half a year, and one year; (2) reversal learning, where the rewarded and unrewarded symbols were swapped; and (3) memory retention, following reversal learning at two-week and half-year intervals. We revealed that (a) initial associative learning memory was strikingly persistent, remaining detectable after nearly 600 days; (b) reversal learning performance was comparable to that of large parrot species; and (c) while the post-reversal forgetting curve mirrored the pattern of initial learning, it exhibited a shorter retention duration and a lower retention plateau. These findings suggest that forgetting may serve as an adaptive mechanism that regulates the retrievability of conflicting information, rather than a simple erasure of memory traces. When the environment changes, the retrievability of previously functional but now maladaptive memories is suppressed, but their long-term storage is preserved for potential future use under analogous circumstances. Such dynamic regulations prevent the repetitive overwriting of information in a fluctuating environment, thereby fostering greater behavioural flexibility across dynamic scenarios.