Panel A: overview of the place-response test. Pigs approached buckets from one entrance during training, learning to find a baited bucket. Pigs needed to find the treat in the baited bucket without investigating the empty bucket for five trials in a row before proceeding to the test phase. In the test phase, the pig approached the buckets from the opposite site of the arena. If the pig had learned the place of the baited bucket, it would go to the baited bucket; if it had learned to turn towards the right on entering (response), it would visit the empty bucket. Panel B: Active pigs that were housed in a standard, stimulus-poor environment (barren, no substrates provided) from birth until testing (eight weeks of age) showed response learning more often than passive pigs. Panel C: Active and passive pigs have similar strategies when they have been housed in a stimulus-rich environment (enriched, more complex environment with substrates for exploration provided) from birth onwards.