Innate vs Learned Behaviors: Reflexes and Imprinting

Innate behavior is behavior that is genetically programmed and performed correctly the first time without learning, while learned behavior is behavior that changes as a result of experience; examples of simple learning include habituation and imprinting. In brief: reflexes and fixed action patterns are innate, such as a newborn’s grasp or a spider spinning its web. Habituation is learning to ignore a harmless repeated stimulus, and imprinting is rapid learning in a critical period, such as ducklings following the first moving object they see. Most behavior combines innate and learned elements.

Ethology, the study of animal behavior, asks both how and why behavior occurs. This guide defines behavior, explains innate behaviors such as reflexes and fixed action patterns, describes habituation and imprinting and other learned behavior, discusses the nature versus nurture debate, compares innate and learned behavior in a table, works through an experimental example and corrects common mistakes.

What is behavior?

Behavior is everything that an animal does in response to stimuli from its environment or from within its body: movement, feeding, courtship, defense and communication. Nobel laureate Niko Tinbergen proposed four questions that ethologists ask about any behavior: its immediate cause (mechanism: what stimulus and which nerves and hormones are involved), its development in the individual (ontogeny), its survival value (function) and its evolutionary history (phylogeny). The first two are called “proximate” explanations, and the last two “ultimate” explanations.

What is innate behavior?

Innate (instinctive) behavior is inherited. It is developed without experience, appears in the same form in all members of a species and is the result of genes that shape the nervous system.

• Reflexes: simple, automatic responses to a stimulus, such as the withdrawal of a limb from a painful stimulus, blinking, or the rooting reflex of newborn babies. They involve few neurons, as described in the article on the reflex arc.
• Taxes and kineses: a taxis is movement toward or away from a stimulus (woodlice move away from light, and moths toward it), and a kinesis is a change in the rate of movement or turning in response to a stimulus (woodlice move faster in dry places and so find humid places by chance).
• Fixed action patterns (FAPs): stereotyped sequences of behavior triggered by a simple stimulus (a sign stimulus), and once started, usually carried to completion. In the classic example from Tinbergen’s studies, a male three-spined stickleback attacks any object with a red underside, even a crude model, because the red belly is the sign stimulus of a rival male. A greylag goose will roll an egg that has rolled out of the nest back with its bill, and it continues the movement even if the egg is removed.
• Complex innate behaviors: web-spinning by spiders, nest building by weaver birds, the waggle dance of honeybees, and migration in some insects. A young spider spins a perfect web without having seen one.

Innate behaviors are valuable when an animal needs to respond correctly the first time, as in finding food or avoiding danger. They are less flexible, and can be misled: gull chicks peck at a red spot on the parent’s bill, but they also peck at a pencil with a red band.

What is learned behavior?

Learned behavior changes through experience. Learning allows animals to adapt to a changing environment during their lifetime. The main forms are:

• Habituation: a decrease in response to a harmless stimulus that is repeated. It is the simplest form of learning, and it lets animals ignore irrelevant stimuli.
• Imprinting: rapid learning at a particular stage of life, the sensitive (critical) period, which is hard to reverse.
• Associative learning: linking two stimuli, or a stimulus and a response, as in classical and operant conditioning, which are explained in the next article.
• Observational (social) learning: learning by watching others. Japanese macaques on Koshima island learned to wash sweet potatoes in the sea after a young female did so in 1953; young chimpanzees learn how to use sticks to get termites from their mothers.
• Insight learning: solving a new problem by reasoning, without trial and error. Wolfgang Köhler’s chimpanzees stacked boxes to reach hanging bananas.
• Spatial learning: learning the layout of the environment: bees learn the position of the hive and flowers.

What are habituation and imprinting?

Habituation: a sea anemone withdraws its tentacles when touched, but if the touches are repeated without any harm, it stops responding. Birds in a city stop flying away from the traffic. It is different from fatigue, because a new stimulus restores the response. It saves energy, and prevents animals from wasting effort on harmless events.

Imprinting: Konrad Lorenz showed in the 1930s that greylag goslings follow the first moving object that they see in the first day or two after hatching. In his experiments, goslings that saw Lorenz first followed him instead of the mother goose, and he is famous for being followed by geese. This is filial imprinting. It ensures that young birds stay with their mother, in nature, and learn what their species looks like. Sexual imprinting shapes the later mating preferences: birds raised by foster parents of another species may later try to mate with that species. Song learning in birds such as zebra finches and white-crowned sparrows has a sensitive period during which the young must hear the song of their own species. Human infants have also a sensitive period for learning language, though it is not strictly imprinting. Imprinting has been used in conservation: young whooping cranes and condors were raised with puppets or costumes so that they would not imprint on humans.

Innate and learned behavior compared

How do nature and nurture interact?

The “nature versus nurture” debate asks whether behavior is genetic or learned. Modern biologists see this as a false choice: nearly all behaviors depend on both genes and environment. Examples:

• Birdsong has a genetic basis (the species’ song template), but the details are learned by hearing adults. Birds raised in isolation sing an abnormal song.
• Predator recognition: many young birds and mammals have an innate fear of certain shapes, but learn which individual predators are dangerous.
• Mammals have an innate drive to play, but learn skills through play.
• Human language ability is innate, but the language that a child learns depends on its environment.

Genes provide a “program” with different degrees of openness to experience. Studies of single genes, such as the for gene in fruit flies, which affects the tendency to forage, show that a gene can alter behavior, but the effect depends on the environment.

Worked example: a habituation experiment

A student investigates habituation in a snail (or a woodlouse). The snail on a smooth surface withdraws into its shell when the surface is tapped. The student taps every 30 seconds and records how long the snail stays withdrawn.

1. Trend: the response falls from 25 seconds to 1 second over 10 taps. This is consistent with habituation.
2. Percentage decline: (25 − 1) ÷ 25 × 100 = 96 percent.
3. Rule out fatigue: after the tenth tap, the student gently blows on the snail (a new stimulus). If the snail withdraws again, the response has not been lost by fatigue of muscles but by a decrease in response to the repeated tap. Then, after a rest of 10 minutes, a tap gives a partial recovery (spontaneous recovery), perhaps 15 seconds.
4. Controls and reliability: use the same strength of tap, the same temperature and time between taps, and use several animals, then calculate the mean. A control group that is not tapped shows that the snails do not change their behavior over the same time by themselves.

The experiment demonstrates learning without reward or punishment. In the sea slug Aplysia, Eric Kandel showed that habituation of the gill-withdrawal reflex is accompanied by a decrease in the release of neurotransmitter at synapses, and he received the 2000 Nobel Prize in Physiology or Medicine for his work on the cellular basis of memory.

How was animal behavior studied?

Konrad Lorenz, Niko Tinbergen and Karl von Frisch founded ethology and shared the 1973 Nobel Prize in Physiology or Medicine. Lorenz studied imprinting in geese, Tinbergen the fixed action patterns of sticklebacks and gulls, and von Frisch the language of bees. In America, comparative psychologists such as B. F. Skinner and Edward Thorndike studied learning in the laboratory. Behavioral ecology and neuroscience have joined these two traditions since the 1970s.

Which mistakes are common?

Mistake 1: Saying that innate behavior cannot change

Innate behaviors can be modified by experience. They are not learned, but they are not completely fixed.

Mistake 2: Confusing habituation with fatigue

With fatigue, the response is lost for all stimuli. With habituation, a new stimulus still causes a response.

Mistake 3: Thinking that imprinting can occur at any age

It happens during a sensitive period, often early in life.

Mistake 4: Treating behavior as only genetic or only learned

Most behavior involves both genes and experience.