Table of Contents
What Is Meant by Ontogeny of Behavior?
In behavioral biology, ontogeny describes the development of an individual organism from conception to death. When we speak of the ontogeny of behavior, we are asking:
- How does an animal’s behavior change during its life?
- Which parts of behavior are present from the beginning?
- Which parts arise only through experience?
- How do genes, environment, and the organism’s own actions interact over time?
The focus here is always on the individual, not the species as a whole (which would belong to evolution).
Ontogeny of behavior includes:
- The appearance of new behaviors (e.g. first feeding behavior in a chick)
- The disappearance of early behaviors (e.g. reflexes in human infants)
- The refinement or reorganization of behavior (e.g. more precise hunting techniques in a predator)
Innate Foundations and the Role of Experience
Every individual starts life with a genetic “equipment” that sets:
- Sensory capabilities
- Motor possibilities (how the body can move)
- Basic neural circuits (e.g. reflex paths, simple behavior patterns)
- Predispositions to react to certain stimuli (e.g. attention to faces in humans, moving objects in chicks)
However, this innate basis is not a finished “behavior program” but a set of possibilities. During ontogeny, these possibilities are shaped by:
- Physical environment (temperature, light, food availability)
- Social environment (parents, siblings, conspecifics, sometimes other species)
- Own activities (what the animal does changes what it experiences)
- Random events (illness, accidents, stress)
Many behaviors emerge from a gene–environment interaction rather than being purely “innate” or “learned”.
Sensitive and Critical Periods in Behavioral Development
During ontogeny, there are time windows in which experience has especially strong or even irreversible effects on behavior.
Critical Periods
A critical period is a limited developmental phase in which:
- A specific experience must occur
- Otherwise a behavior does not develop normally or at all
Characteristics:
- Narrow time window
- Changes often irreversible
- Typically linked to key adaptive tasks (e.g. recognizing parents, learning species-specific song)
Classic examples (conceptual, details belong in other chapters):
- Visual system development in mammals: early visual deprivation can permanently impair normal vision.
- Imprinting in birds (see below): irreversible attachment to a parent figure.
Sensitive Periods
A sensitive period is a developmental phase in which:
- Certain experiences are especially effective
- But effects can still be partially compensated before or after that period
Characteristics:
- Broader time window
- Effects often strong, but not absolutely irreversible
- “Optimal” time for particular learning processes
Examples:
- Acquisition of species-typical vocalizations
- Acquisition of complex motor skills or social behaviors
Sensitive periods highlight that timing of experience is crucial: the same stimulus can have different effects depending on when in ontogeny it occurs.
Imprinting as a Special Form of Early Learning
Imprinting is a striking example of ontogenetic shaping of behavior and illustrates critical periods.
Key properties of imprinting:
- Occurs in a narrowly limited early phase (imprinting phase)
- Requires specific stimuli from the environment (often a parent or parent-like object)
- Results in long-lasting, often irreversible changes in behavior
- Does not require reinforcement (no reward or punishment necessary)
- Very specific: only certain stimuli can trigger imprinting
Types include, for example:
- Filial imprinting: young animals (e.g. many birds) learn who their parents or “leader” are and later follow them.
- Sexual imprinting: later partner preferences are influenced by early experiences with conspecifics.
Imprinting shows:
- Behavior can be heavily influenced by experience
- This influence is only possible during a tightly limited ontogenetic window
- Once established, the behavior appears “innate” but is actually the result of an early learning process.
Maturation vs. Learning
Behavioral development involves two interacting processes:
Maturation
Maturation refers to changes that:
- Result primarily from internal growth and differentiation of the body and nervous system
- Occur according to a species-specific timetable
- Require only minimal external stimulation to unfold
Examples:
- Development of muscle strength and coordination enabling a young animal to stand or fly
- Myelination of nerve fibers enhancing conduction speed
- Emergence of hormonal cycles affecting reproductive behaviors
Maturation often makes certain behaviors possible but does not determine their exact form.
Learning
Learning refers to relatively lasting changes in behavior based on:
- Individual experience with the environment
- Practice and feedback from consequences of actions
Ontogeny of behavior can rarely be understood by looking at maturation or learning alone. Typical patterns:
- A behavior becomes physically possible through maturation (e.g. wings fully grown)
- Its specific form is shaped by learning and practice (e.g. efficient flight maneuvers)
Self-Generated Experience: The Active Role of the Organism
Individuals are not passive recipients of stimuli. Even simple animals:
- Explore their surroundings
- Try out behaviors
- Generate patterns of stimulation for themselves
Through this:
- They select which environmental aspects they experience
- They reinforce or avoid certain situations
- They “construct” part of their own behavioral environment
Examples of self-generated experience:
- Play behavior in young mammals and birds
- Exploratory behavior (sniffing, touching, manipulating objects)
- Trial-and-error in acquiring skills (e.g. hunting, object use)
This shows that ontogeny of behavior is not just “environment acts on genes,” but a three-way interaction:
- Genetic predispositions
- Environmental conditions
- The animal’s own activity
Stages and Sequences in Behavioral Ontogeny
Behavioral ontogeny often follows typical, species-specific sequences of stages. These stages:
- Are linked to physical development (size, musculature, brain maturation)
- Are adapted to ecological needs at each life stage
- Prepare the animal for future phases (e.g. play preparing for adult fighting or hunting)
Examples of stage-related changes:
- Dependence → independence (from parental care to self-sufficiency)
- Restricted behavioral repertoire → broader, more complex repertoire
- Strong plasticity early → increasing stabilization of behaviors later
Ontogeny is thus not simply “more of the same” but involves:
- Appearance of new behaviors
- Reorganization of old behaviors
- Shifts in motivational priorities (e.g. from play to mating behavior)
Social Environment and Behavioral Development
For many species, the social environment is a decisive part of ontogeny.
Social influences can:
- Provide necessary stimuli for the development of normal social behavior (greetings, play, hierarchy behavior)
- Shape later partner choice and parental behavior
- Influence fear and aggression patterns (what is perceived as threat or safe)
Lack of adequate social experience in sensitive periods can lead to:
- Deficits in social competence
- Fear or aggression disorders
- Atypical or reduced reproductive behavior
In highly social animals (including humans), the social environment is one of the strongest factors in individual behavioral development.
Stability and Plasticity of Behavior Over the Lifespan
Ontogeny of behavior is characterized by a balance between:
- Stability: species-typical patterns that remain relatively constant (e.g. basic motor patterns, certain displays)
- Plasticity: capacity to adapt behavior to individual life circumstances
General trends:
- High plasticity in early developmental phases (many possibilities, much still “open”)
- Gradual stabilization: frequently used behaviors are strengthened, rarely used ones are weakened
- In some species, plasticity remains high throughout life; in others, it declines strongly after early phases
This balance ensures:
- Basic survival functions are reliably available
- Individual adaptation to specific, local conditions is still possible
Ontogeny of Behavior as an Evolutionary Product
Finally, the way behavior develops in the individual is itself an evolutionary adaptation. Natural selection acts not only on:
- Which behaviors an adult shows,
but also on: - How and when these behaviors arise during ontogeny.
Adaptive aspects of behavioral ontogeny include:
- Timing of sensitive and critical periods
- Duration of dependence on parents
- Amount and type of play and exploration
- Degree of lifelong plasticity
Thus, ontogeny of behavior links:
- The genetic heritage of the species
- The unique life history of the individual
- The ecological and social environment in which that life unfolds.