personally I've had more engaging eye contact with a pig (who we then proceeded to turn in to a variety of sausages) compared with any other animal. falling back to the various studies showing how the dilation of pupils relates directly with cognition, it suffices to say that you can gage someone's intelligence by looking in to their eyes. it is not then a stretch to see that a pig is intelligent when it catches eyes with you (which not that many animals can do).