The Oblong Effect

Animals prefer mixtures of length and roundness.

“A death’s-head!” echoed Legrand — “Oh — yes — well, it has something of that appearance upon paper, no doubt. The two upper black spots look like eyes, eh? and the longer one at the bottom like a mouth — and then the shape of the whole is oval.”

— Edgar Allan Poe, The Gold Bug


Flowers, Fruits, Nuts and Eggs
Oblong Things in Animals
Elongated Cultural Things
Sensory Bias Versus Adaptation
Aesthetic Interactions
Works Cited

A universal sensory bias favoring oblong things is probably responsible for human and animal decorations being, very often, not too long, not too short, not quite spherical or square, but elongated somewhat along one dimension, and more often than should be expected by chance with no obvious corresponding advantage to explain it practically beyond an intrinsic appeal to the senses.

Being oblong instead of perfectly round probably makes an object look more complex, familiar and likable to an animal. The effect can be seen generally in the shapes of aesthetic objects in human culture, the shapes of animals and their parts, and those of fruits and flowers which exploit us to spread their pollen and seeds.

The idea of “effect” used here is borrowed from the way Thayer (1896) used it to denote the fact that animals are usually darker on top and brighter below. Thayer’s pattern is probably better understood in terms of mate choice and general aesthetic biases than as a way of hiding in sunlight, which has been assumed. The oblong effect is similar to Thayer’s because it’s also ubiquitous, and because it’s far easier to imagine it having arisen in response to universal biases in the animal brain than through random chance or many independent adaptive evolutionary events.

Flowers, Fruits, Nuts and Eggs

Almost every flower petal is longer in one dimension than the other, suggesting that pollinators like the oblong look. It’s also typical in flowers for one end of the petals to be pointier than the other, implying that insects have been amused with a little asymmetry, in addition to a little elongation, as their decisions have driven the evolutionary transformation of leaves into flower petals.

Fruits and seed-dispersing foods like strawberries, lemons, watermelons, avocados, pears and pumpkins are oblong. Nuts like acorns, walnuts, almonds, and sunflower seeds, and other foods such as beans, corn and rice are typically oblong. Eggs in birds, like petals and strawberries, are not only oblong, but a bit pointer on one end than the other. Stoddard et al. (2017) studied the eggs of 1,400 bird species and found that they vary continuously in degree of oblongness and pointedness. It’s clear from their results that egg shapes cluster around an average with a moderate amount of each quality.

The question of why eggs are oblong has been debated and approached from numerous angles without a clear conclusion. Whatever adaptive purpose might be determined would have to explain similar shapes in the eggs of reptiles, dinosaurs and the duck-billed platypus (Ornithorhynchus anatinus). Thus, explanations having to do specifically with being a bird or flying are probably not realistic. One thing we should expect from every egg-laying animal, though, and regardless of its particular life history, is an appreciation for eggs in the context of parental care. Egg-laying animals should like the way eggs look. Eggs should have shapes a parent sees as valuable and worthy of attention. A simple bias for the slightly long and pointy in parents would account for an evolutionary change in egg shape away from roundness, toward the preferred shape, maintain the change, and do so without having to assume multiple, improbable instances of evolutionary convergence.

Oblong Things in Animals

Oblong is the shape of mysterious eyespots in peacocks, spots in many butterfly species, egg-spots in cichlids, ornamental spots in guppies (Poecilia reticulata), the shape assumed by the superb bird-of-paradise (Lophorina superba) during his mating dance, the shape of the decorated abdomen used in male jumping spider (family Salticidae) courtship, the spots of ladybugs, Dalmatians, the spotted hyena (Crocuta crocuta), leopards (Panthera pardus) and jaguars (Panthera onca). In humans the head and eyes appear to exhibit the oblong effect, and these, like flower petals, strawberries, peacock eyespots and eggs, are slightly pointier at one end than the other.

Elongated Cultural Things

Within human culture moderately elongated aesthetic visual objects include, in overall shape, among other things, most paintings, photos, cell phones, mirrors, computers, televisions, flags of states, badges, coats of arms, tombstones, prehistoric sculptures, Stonehenge stones, ancient amphitheaters, Easter Island stone figures, Easter eggs, rugs, windows, books, footballs, flying saucers and the icon of, which depicts a circle on the left, an oblong shape in the middle and a long one on the right.

Oblongness appears widely in creation stories as a “cosmic egg,” including the Ancient Greek Orphic Egg, the Chinese Taoist Egg of Pangu, the Egyptian Cosmic Egg of Ra, the Japanese Egg of Chaos and the Golden Egg in the Vedic tradition. The cross, used in various religious contexts throughout history, and presumably more interesting than a plus sign, or a plus sign with one line shorter than the other, is in a sense the same type of shape as an egg, a strawberry, human head or peacock eyespot because it’s longer in one dimension than the other and it’s pointier at one end. Oblong bias may relate to the prevalence of the golden rectangle in biology and to the apparently universal dichotomy between the names we give round versus spiky shapes, known as the Bouba-Kiki effect (observed by Köhler 1970, see Fort et al. 2014). It might relate as well to the fat/thin effect described by Milan et al. (2013).

A universal bias for moderate elongation is likely to have observable consequences in human art and idiomatic language. It should be captured in numerous expressions, particularly otherwise nonsensical things we seem to say just for fun, idioms with no real relevance to the circumstances when we use them, such as “the long and short of it,” “to make a long story short” and “the short end of the stick.” The idea of coupling a long object with a round one, an extreme version of the fat/thin effect, appears repeatedly in myth, art and language as well. Oblong bias, golden ratios, fat/thin, long/short and long/round effects might all be products of a more general universal preference for moderate elongation.

Sensory Bias Versus Adaptation

The best way to account for oblong shapes showing up repeatedly in phenomena which are likely under selection to be appealing is assuming a fundamental, universal sensory bias is responsible. The problems of ubiquity and persistence in oblong ornaments would be settled, and the relevant question would be how and why the bias is embodied in the brain at such a fundamental level, or what could be similar enough about every animal brain to cause a slight, universal preference for the oblong over the round.

A universal bias would have caused animals with eggs to favor oblong eggs over round ones, pollinators to favor oblong petals, fruit eating animals to favor oblong fruit, nut and bean eating animals to choose oblong ones, animals to favor oblong body shapes and parts, round spots to become less round through mate choice and humans to emphasize the shape in the way we design things and decorate our surroundings.

Otherwise it seems necessary to determine what shaped the psychology of so many very different animals to prefer the shape, so consistently over extremely long periods of time, and make those determinations one population, species, or taxonomic group at a time, trying to find anatomical or life history reasons which are very unlikely to be common to every animal in which the oblong effect can be seen, or conduct large correlational studies comparing degrees of oblongness to variation in any number of other ecological factors. If results from experiments show a potential function for the oblong shape in animal eggs, the function doesn’t extrapolate to spots, eyes, or flower petals.

A curious example of how animals have apparently evolved to exploit a bias favoring long/short effects, or visual mixtures of length and roundness, exists in the bowerbirds. They have a tendency to collect large numbers of both long and short objects like straws and bottle caps and laying them out for display in intricate ways, often interspersed, around the entrances to their bowers trying to coax a female into mating.

How an oblong bias is embodied in the mind is a mystery. The animal brain is oblong and pointier on one end, but the phenomenon probably has deep explanations having to do with small scale, physical variation in brains, similar to other biases favoring simple opposites such as those described in the story Painted by Nature.

Aesthetic Interactions

The longer an object becomes the more exciting we tend to find it. The rounder it is, the less exciting. A rectangular or oval-shaped object represents a kind of moderation, a mixture we appreciate. An oblong bias is one of several biases universal to animals favoring juxtapositions between simple opposites. These biases often interact in an aesthetic experience.

Animals are prone to disrupt round objects, adding qualities we associate universally with greater excitement than roundness such as motion (e.g., dance, spatulate tail feathers, ball sports), brightness (e.g., apples, oranges, happy faces), spikiness (e.g., horns, tails, spikes, spines, eyelashes, whiskers, hair), upwardness (e.g., peacocks, jumping spiders, ball sports) and multiplicity (e.g., spots, polka dots, candy). Thus elongation is only one of several ways to make a round object look more exciting from the perspective of an animal.

Works Cited

Fort, Mathilde, et al.Consonants Are More Important than Vowels in the Bouba-Kiki Effect.” Language and Speech, vol. 58, no. 2, 2014, pp. 247–266., doi:10.1177/0023830914534951.

Köhler, Wolfgang. Gestalt Psychology: An Introduction to New Concepts in Modern Psychology. United States, Liveright, 1970.

Milan, E et al. “The Kiki-Bouba Effect A Case of Personification and Ideaesthesia.” Journal of Consciousness Studies, vol. 20, 2013.

Stoddard, Mary Caswell, et al. “Avian Egg Shape: Form, Function, and Evolution.” Science 356.6344 (2017): 1249–1254.

Thayer, Abbott H. “The Law which Underlies Protective Coloration.” The Auk 13.2 (1896): 124–129.

Life in terms of the nonliving. Universal animal preferences for mixtures of simple, more and less exciting psychological opposites.

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