Behavioral plasticity refers to a change in an organism's behavior that results from exposure to stimuli, such as changing environmental conditions. Behavior can change more rapidly in response to changes in internal or external stimuli than is the case for most morphological traits and many physiological traits. As a result, when organisms are confronted by new conditions, behavioral changes often occur in advance of physiological or morphological changes. For instance, larval amphibians changed their antipredator behavior within an hour after a change in cues from predators, but morphological changes in body and tail shape in response to the same cues required a week to complete.

Background

For many years, ethologists have studied the ways that behavior can change in response to changes in external stimuli or changes in the internal state of an organism. In a parallel literature, psychologists studying learning and cognition have spent years documenting the many ways that experiences in the past can affect the behavior an individual expresses at the current time. Interest in behavioral plasticity gained prominence more recently as an example of a type of

phenotypic plasticity Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...

with major consequences for evolutionary biology.

Types

Behavioral plasticity can be broadly organized into two types: exogenous and endogenous. Exogenous plasticity refers to the changes in

behavioral phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prope ...

(i.e., observable behaviors) caused by an external stimulus, experience, or environment. Endogenous plasticity encompasses plastic responses that result from changes in internal cues, such as genotype, circadian rhythms, and menstruation. These two broad categories can be further broken down into two other important classifications. When an external stimulus elicits or "activates" an immediate response (an immediate effect on behavior), then the organism is demonstrating contextual plasticity. This form of plasticity highlights the concept that external stimuli in a given context activate neural and

hormonal A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required f ...

mechanisms or pathways which already exist inside the organism. In contrast, if an organism's current behavior is altered by past experiences, then the animal is said to be exhibiting developmental or "innate" behavioral plasticity. This form of plasticity is generally thought to require new neuronal pathways to form. Developmental behavioral plasticity corresponds to the commonly used definition of plasticity: a single genotype can express more than one behavioral phenotype as a result of different developmental routes triggered by differences in past experiences. Developmental plasticity thus includes what is referred to as " learning". However, developmental plasticity also includes developmental changes in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

and

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

relevant to a particular behavior, such as changes in muscles, limbs, or bones that influence foraging or locomotion throughout and organism's life. A major difference between developmental and contextual plasticity is the inherent trade-off between the time of interpreting a stimulus and exhibiting a behavior. Contextual plasticity is a near immediate response to the environment. The underlying hormonal networks/neuronal pathways are already present, so it is only a matter of activating them. In contrast, developmental plasticity requires internal changes in hormonal networks and neuronal pathways. As a result, developmental plasticity is often, although not always, a slower process than contextual plasticity. For instance,

habituation Habituation is a form of non-associative learning in which an innate (non-reinforced) response to a stimulus decreases after repeated or prolonged presentations of that stimulus. Responses that habituate include those that involve the intact org ...

is a type of learning (developmental plasticity) that can occur within a short period of time. One of the advantages of developmental behavioral plasticity that occurs over extended periods of time is that such changes can occur in concert with changes in morphological and physiological traits. In such cases, the same set of external or internal stimuli can lead to coordinated changes in suites of behavioral, morphological and physiological traits.

Examples

Contextual plasticity is typically studied by presenting the same individual with different external stimuli, and then recording their responses to each stimulus. For instance,

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

s can rapidly alter their running speed in response to changes in the external temperature. Another example of contextual plasticity occurs when birds change their vocalizations in response to changes in the pitch or intensity of background noise. Contextual plasticity plays a major role in studies of

mate preference Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choic ...

, in which each subject is exposed to cues from different mates, and its response to each cue is quantified. In this case, a stronger attractive response to a particular cue is assumed to reflect a preference for mates with that cue. Developmental plasticity encompasses the many ways that experiences in an organism's past can affect its current behavior. Developmental plasticity thus includes learning, acclimation, and any situation in which environmental conditions early in life affects the behavior expressed later in life (also called ontogenetic plasticity. Since a given individual can only be raised under one set of conditions, ontogenetic plasticity is studied by dividing matched individuals into two or more groups, and then rearing each group under a different set of conditions. For instance, this experimental design was used to demonstrate that the density at which moth larvae were raised affected the courtship signals that they produced as adults. Endogenous plasticity includes circadian rhythms, circannual rhythms, and age-dependent changes in behavior. A good example of endogenous plasticity occurs with

zebrafish The zebrafish (''Danio rerio'') is a freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often ca ...

(''Danio rerio''). Larval zebrafish exhibit circadian rhythms in their responsiveness to light. Even when they are maintained under continuous darkness, the fish are much more responsive to changes in light (i.e. higher contextual plasticity) during subjective day than during subjective night. Another example involves the changes in an individual's behavior and hormonal profile around the time of

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...

; such changes are affected changes in physiology that occurred months to years earlier in life.

Potential vs. realized plasticity

A useful distinction to make when looking at behavioral plasticity is between potential and realized plasticity. Potential plasticity refers to the ability of a given phenotypic trait to vary in its response to variation in stimuli, experiences, or environmental conditions. Thus, potential plasticity is the theoretical range in behavioral plasticity that could be expressed. This value is never truly known, but serves more as a baseline in plasticity models. Realized plasticity, on the other hand, refers to the extent to which a given phenotype actually varies in response to changes in a specific stimulus, experience, or environmental condition.

Individual differences in behavioral plasticity

Recent studies of animals have documented individual differences in virtually all of the different types of behavioral plasticities described above. In addition, behavioral plasticities may themselves be developmentally plastic: individual differences in a type of plasticity that is expressed at a given age may be affected by the conditions to which the subjects were exposed earlier in life. In a variety of species, for instance, social cues during the juvenile period affect the contextual plasticity of responses to cues from potential mates at adulthood. As is the case for many other types of plasticity, researchers studying the development of individual differences in behavioral plasticity have found that genes, prior experiences and interactions between these factors contribute to the individual differences in behavioral plasticity that are expressed at a given age or lifestage. Another question that is currently attracting interest from students of both animal and human behavior is whether different types of behavioral plasticities are correlated with one another across individuals: i.e., whether some individuals are generally more plastic than others. Although there is some evidence that certain types of cognitive traits tend to be positively correlated with one another across individuals (see the g factor in humans), at present there is scant evidence that other types of plasticity (e.g. contextual plasticity and ontogenetic plasticity) are correlated with one another across individuals or genotypes in humans or animals.

Evolutionary causes and consequences

Behavioral plasticity can have major impacts on the

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

ary fitness of an individual. Both developmental and contextual plasticity influence the fitness of an animal in a novel environment by increasing the probability that the animal will survive in that environment. Developmental plasticity is particularly important in terms of survival in novel environments, because trial-and-error processes such as learning (which encompass both phenotype sampling and environmental feedback) have the ability to immediately shift an entire population close to a new adaptive norm. As such, the ability to express some level of behavioral plasticity can be very advantageous. In fluctuating environments, animals that can change how they respond to differences in stimuli would have a leg up over animals that were set in a rigid phenotype. However, this would only be the case if the costs of maintaining the ability to change phenotype was lower than the benefit conferred to the individual.

References

{{reflist, refs= {{cite book , last=West-Ebberhard, first=MJ , year=2003 , title=Developmental Plasticity and Evolution , publisher=Oxford University Press , isbn=9780195122350 {{cite journal , last=Snell-Rood, first=EC , year=2013 , title=An overview of the evolutionary causes and consequences of behavioural plasticity , journal=Animal Behaviour , volume=85, issue=5 , page=1004 , doi=10.1016/j.anbehav.2012.12.031 , s2cid=53188749 {{cite journal , last1=Mery, first1=F , last2=Burns, first2=J , date=May 2010 , title=Behavioural plasticity: an interaction between evolution and experience , journal=Evolutionary Ecology , volume=24, number=3, pages=571–583 , doi=10.1007/s10682-009-9336-y , s2cid=45562817 {{cite journal , last=Andrew, first=N.R. , year=2013 , title=Can temperate insects take the heat? A case study of the physiological and behavioural responses in a common ant, ''Iridomyrmex purpureus'' (Formicidae), with potential climate change. , journal=Journal of Insect Physiology , volume=59, issue=9 , pages=870–880 , doi=10.1016/j.jinsphys.2013.06.003 , pmid=23806604 {{cite journal , last=Zhou, first=Y , year=2008 , title=Reaction norm variants for male calling song in populations of ''Achroia grisella'' (Lepidoptera: Pyralidae): toward a resolution of the lek paradox , journal=Evolution , volume=62, issue=6 , pages=1317–1334 , doi=10.1111/j.1558-5646.2008.00371.x , pmid=18346222 , s2cid=17499218 , url=https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=16580&content=PDF , doi-access=free {{cite journal , last=Emran, first=B.J , year=2011 , title=Zebrafish larvae lose vision at night , journal=Proceedings of the National Academy of Sciences of the United States of America , volume=107, issue=13 , pages=6034–6039 , doi=10.1073/pnas.0914718107 , pmid=20224035 , pmc=2851871 , doi-access=free {{cite journal , last1=Orizaola , first1=Germán , last2=Dahl , first2=Emma , last3=Laurila , first3=Anssi , title=Reversibility of predator-induced plasticity and its effect at a life-history switch point , journal=Oikos , volume=121 , issue=1 , year=2012 , pages=44–52 , issn=0030-1299 , doi=10.1111/j.1600-0706.2011.19050.x {{cite book, veditors=Binder MD, Hirokawa N, Windhorst U , title=Encyclopedia of neuroscience , date=2009 , publisher=Springer , location=Berlin , isbn=978-3-540-23735-8 , page=372 , doi=10.1007/978-3-540-29678-2_594 , chapter= Behavioral Plasticity {{cite journal, last1=Stamps, first1=Judy A., title=Individual differences in behavioural plasticities, journal=Biological Reviews, volume=91, issue=2, year=2016, pages=534–567, issn=1464-7931, doi=10.1111/brv.12186, pmid=25865135, s2cid=10433665 Behavioral ecology Evolutionary biology Behavior modification Behavioral neuroscience