Study into long-term memory of a complex learning task in Shetland ponies (Equus caballus)

Three Shetland ponies were tested in memorizing a quantity discrimination task with a computer based learning device. One year before, they had learned to relate a quantity of geometric symbols to another on a computer flat screen presented in a matching to sample design. All three of the ponies solved the task to discriminate between the quantities 4 vs. 5. After a delay of one year, animals were re-tested with an identical test procedure with a quantity discrimination of 3 vs. 2 and the original matching to sample task. None of the animals could recall the discrimination task, while the instrumental task of the test procedure was instantly performed correctly. Considering the evidence on multiple memory systems, we suggest that learning of the motor sequence of the test procedure and learning of the higher-order cognition task involved different parts of the brain and were possibly also encoded, stored and recalled in different ways. The ponies were not involved in any other training, learning tests or activities in the interim. Thus, we suggest that continuous learning and training stimuli might enhance the retention of a complex learning task like the quantity judgment, based on a matching to sample arrangement. These results give implications for further research in the field of learning, memory and training of the horse.