Why Do Anime Characters Have Big Eyes?
When you introduce new people to anime, this is the question that most often comes up. How would you answer it?
Japanese Art History
Japanese aesthetics traditionally value the ability of the artist to make the viewer feel strong emotions, rather than the classical Western ideal of using art to make perfection of form, but in a realistic way. As such, manga artists always seem to have preferred character designs that emphasized the beauty and emotional appeal of their characters, over showing them as people with realistic bodies. This general tendency is most noticeable in the often large eyes, but the characters also often have unrealistic features in other ways.
Since Osamu Tezuka, creator of Astroboy, is considered the "father of manga", his style was influential to later anime and manga artists. His main influences were American cartoon characters with big eyes, such as Donald Duck, Mickey Mouse, and Betty Boop. In those cases, the large eyes were drawn simply to exaggerate the facial expressions. This style simply ended up becoming popular because emphasizing the face and facial expression is important in sequential art storytelling.
One cultural anthropologist believes that some Japanese artists may have chosen to make their characters' eyes big because it made their work have more international appeal, looking less Asian. But that seems unlikely to me, given that they made most of that stuff, especially back in the early days, for a strictly Japanese audience, with Western fans being something of an afterthought to most of the artists. I mean, the same goes for me, if I were writing a science fiction novel; I would think about the audience as my own country first, obviously.
In the Victorian/Meiji era, newly opened trade with the west might have also had an influence on Japanese art and visual culture, especially in the trade to Japan of porcelain dolls, which had big, round eyes. The popularity of western-style dolls among Japanese girls and women might have been an early influence on shoujo, or girls' manga.
Are eyes symbolic of greater spirituality or enlightenment? In America, we say that a person's eyes are "the windows to the soul". Indeed, the eye style of a Japanese anime character seem to reflect their personality a great deal. Idealistic characters are literally "wide-eyed", and wise, tough, and older characters have narrower eyes. The eyes also express personality through color, just like the hair usually does. Certainly not being restricted to narrow, realistic eyes makes anime and manga artists able to have more freewheeling creativity when it comes to character design. Which really is not that different as when Disney gives its heroines big eyes.
So why do anime characters have big eyes? Most people would give the oft-repeated Tezuka-Disney answer and leave it at that. However, there are many reasons besides this. One has to go back further in history and wonder, then, why did Disney choose to make characters with such big eyes, and why were they successful? I think that big eyes ultimately speak to a quirk in human psychology; we're neurologically wired to respond to faces. Big eyes signify a helpless child who needs our attention, so the bigger the eye, the more we're compelled by a face, and when such a face emotes, we probably respond more strongly.