Euro-update 4: Sperm whale perception
Tuscany is about the last place you might think to go to speculate about the visual system of a whale, but when you’re spending three weeks relaxing in a secluded villa, you have a lot of reading time. I’ve been reading Moby-Dick.
Herman Melville describes the sperm whale with almost obsessive detail in the book, from the shape of its tail to the nature of its skin.
In one chapter, devoted to contrasting the head of the right whale and the sperm whale, we find amazing speculation about both the human and sperm whale visual system. Remember, this was published in 1851:
Far back on the side of the head, and low down, near the angle of [a] whale’s jaw, if you narrowly search, you will … see a lashless eye….
Now, from this peculiar sideway position of the whale’s eyes, it is plain that he can never see an object which is exactly ahead, no more than he can one exactly astern. In a word, the position of the whale’s eyes corresponds to that of a man’s ears; and you may fancy, for yourself, how it would fare with you, did you sideways survey objects through your ears. You would find that you could only command some thirty degrees of vision in advance of the straight side-line of sight; and about thirty more behind it. If your bitterest foe were walking straight towards you, with dagger uplifted in broad day, you would not be able to see him, any more than if he were stealing upon you from behind.
It may be that our vision system is so entwined with our nature that it wouldn’t be possible to be human and have a vision system like a whale’s. Melville latches on to a crucial implication:
The peculiar position of the whale’s eyes, effectually divided as they are by many cubic feet of solid head, which towers between them like a great mountain separating two lakes in valleys … must wholly separate the impressions which each independent organ imparts. The whale, therefore, must see one distinct picture on this side, and another distinct picture on that side; while all between must be profound darkness and nothingness to him.
That final claim might be overstating things a bit, but Melville moves on to discuss the implications of this arrangement in a fascinating analysis:
So long as a man’s eyes are open in the light, the act of seeing is involuntary; that is, he cannot then help mechanically seeing whatever objects are before him. Nevertheless, any one’s experience will teach him, that though he can take an indiscriminating sweep of things at one glance, it is quite impossible for him, attentively, and completely, to examine any two things — however large or however small — at one and the same instant of time; never mind if they lie side by side and touch each other. But if you now come to separate these two objects, and surround each by a circle of profound darkness; then, in order to see one of them, the other will be utterly excluded from your contemporary consciousness. How is it, then, with the whale? True, both his eyes, in themselves, must simultaneously act; but is his brain so much more comprehensive, combining, and subtle than man’s that he can at the same moment of time attentively examine two distinct prospects, one on one side of him; and the other in an exactly opposite direction? If he can, then it is as marvellous a thing in him, as if a man were able simultaneously to go through two the demonstrations of two distinct problems in Euclid. Nor, strictly investigated, is there any incongruity in this comparison.
That’s a fascinating question. Might a whale, unlike a human, be able to attend to two different objects simultaneously? How would the whale’s conception of the world then differ from our own? Would other senses come into play? Why would it be adaptive for a whale to have a massive blind spot directly in front of its body?