At first glance, Bowlby's attachment theory makes perfect sense. It seems only right that our earliest relationships become an important part of our lives, and that the internal working models guide us throughout future relationships. However, even though attachment theory makes good sense, we have to evaluate the empirical evidence used to support it. There are several questions we must ask ourselves about the ethological approach to attachment. Lorenz's (1952) studies on imprinting in geese may be persuasive, but what can animal studies really tell us about our human bonding behaviors? How do we know that infant attachment is not merely a function of feeding? And what about the phenomenon of a secure base and internal working model? Do they exists or are they just vague concepts, unsupported by data? Also, if attachment security exists, we should be able to classify and measure it. Are the tools used by attachment theorists valid? Can they be used cross-culturally?