Abstract
Modern cephalopods are the most intelligent invertebrates with keen vision which is important for them to move rapidly for successful predation, camouflage for danger avoidance and communicate in complex ways with their body patterns. Therefore, vision might impact the cognition of cephalopods to some degree, but knowledge about how visual information is processed in the perceptual level is still not completely understood. In this work, we investigated the intelligence developing in a different way from vertebrates by observing the cognitive behaviors of cuttlefish. Results from this research are expected to give insights into the visual processing mechanism of cuttlefish. Cuttlefish (Sepia pharaonis) were trained to discriminate figures of shrimp and fish. Training for discrimination was based on operant conditioning and was given in the home tanks of each animal. Experimental apparatus was composed of two separated regions, and cuttlefish had to enter the rewarded area where the rewarded figure was presented or even to strike the rewarded figure with their tentacles for food. After cuttlefish achieved the learning criteria, a discrimination task was conducted to confirm learning. The non-rewarded figure was replaced with a crab figure in the discrimination test. Several transfer tests utilizing novel stimuli which are modified versions of training figures followed up the discrimination test. The outcome of visual processing in cuttlefish was examined in these transfer tasks. The results show that cuttlefish are capable of discriminating figures of fish, shrimp and crab. Furthermore, they do generalize the small-scale, sketch, and silhouette of the training figures, and respond properly, though the response strength is lower than that in training and individual differences exist in performance. In addition, cuttlefish also recognize the fragmented image of the training figures. These findings suggest that cuttlefish have the ability of discrimination, generalization, and amodal completion.