Behavioral plasticity

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Behavioral plasticity refers to a change in an organism's behavior that results from exposure to stimuli, such as changing environmental conditions. [1] 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. [2]

Contents

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. [3] 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. [4] Interest in behavioral plasticity gained prominence more recently as an example of a type of phenotypic plasticity with major consequences for evolutionary biology. [5] [6]

Types

Behavioral plasticity can be broadly organized into two types: exogenous and endogenous. [7] Exogenous plasticity refers to the changes in behavioral phenotype (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. [6] [7] This form of plasticity highlights the concept that external stimuli in a given context activate neural and hormonal mechanisms or pathways which already exist inside the organism. [6] 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. [8] 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 and physiology relevant to a particular behavior, such as changes in muscles, limbs, or bones that influence foraging or locomotion throughout and organism's life. [6]

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 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, ants can rapidly alter their running speed in response to changes in the external temperature. [9] 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, 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. [7] 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. [10] Endogenous plasticity includes circadian rhythms, circannual rhythms, and age-dependent changes in behavior. A good example of endogenous plasticity occurs with zebrafish (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. [11] Another example involves the changes in an individual's behavior and hormonal profile around the time of sexual maturity; such changes are affected changes in physiology that occurred months to years earlier in life. [6]

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. [7] 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. [12] 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 evolutionary 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.

Related Research Articles

Behavior or behaviour is the actions and mannerisms made by individuals, organisms, systems or artificial entities in conjunction with themselves or their environment, which includes the other systems or organisms around as well as the (inanimate) physical environment. It is the computed response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary.

Phenotype Composite of the organisms observable characteristics or traits

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 properties, its behavior, and the products of behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code, or its genotype, and the influence of environmental factors. Both factors may interact, further affecting phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and then again in his 1982 book The Extended Phenotype suggested that one can regard bird nests and other built structures such as caddis-fly larvae cases and beaver dams as "extended phenotypes".

Classical conditioning refers to a behavioral mechanism in which a biologically potent stimulus is paired with a previously neutral stimulus. It also refers to the learning process that results from this pairing, through which the neutral stimulus comes to elicit a response that is usually similar to the one elicited by the potent stimulus.

A taxis is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism in that in the case of taxis, the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.

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 organism or those that involve only components of the organism. The broad ubiquity of habituation across all biologic phyla has resulted in it being called "the simplest, most universal form of learning...as fundamental a characteristic of life as DNA." Functionally-speaking, by diminishing the response to an inconsequential stimulus, habituation is thought to free-up cognitive resources to other stimuli that are associated with biologically important events. For example, organisms may habituate to repeated sudden loud noises when they learn these have no consequences. A progressive decline of a behavior in a habituation procedure may also reflect nonspecific effects such as fatigue, which must be ruled out when the interest is in habituation. Habituation is clinically relevant, as a number of neuropsychiatric conditions, including autism, schizophrenia, migraine, and Tourette's, show reductions in habituation to a variety of stimulus-types both simple (tone) and complex (faces).

In animal dormancy, diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is a physiological state with very specific initiating and inhibiting conditions. The mechanism is a means of surviving predictable, unfavorable environmental conditions, such as temperature extremes, drought, or reduced food availability. Diapause is observed in all the life stages of arthropods, especially insects. Embryonic diapause, a somewhat similar phenomenon, occurs in over 130 species of mammals, possibly even in humans, and in the embryos of many of the oviparous species of fish in the order Cyprinodontiformes.

The thrifty phenotype hypothesis says that reduced fetal growth is strongly associated with a number of chronic conditions later in life, including coronary heart disease, stroke, diabetes, and hypertension. This increased susceptibility is said to result from adaptations made by the fetus in an environment limited in its supply of nutrients. The thrifty phenotype is a component of the fetal origins hypothesis.

Servicescape

Servicescape is a model developed by Booms and Bitner to emphasize the impact of the physical environment in which a service process takes place. The aim of the servicescapes model is to explain behavior of people within the service environment with a view to designing environments that does not accomplish organisational goals in terms of achieving desired behavioural responses. For consumers visiting a service or retail store, the service environment is the first aspect of the service that is perceived by the customer and it is at this stage that consumers are likely to form impressions of the level of service they will receive.

Relational frame theory (RFT) is a psychological theory of human language. It was developed originally by Steven C. Hayes of University of Nevada, Reno and has been extended in research, notably by Dermot Barnes-Holmes and colleagues of Ghent University.

Polyphenism Type of polymorphism where different forms of an animal arise from a single genotype

A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity.

Phenotypic plasticity Trait change of an organism in response to environmental variation

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 encompasses all types of environmentally induced changes that may or may not be permanent throughout an individual's lifespan. The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as acclimation (acclimatization), as well as learning. The special case when differences in environment induce discrete phenotypes is termed polyphenism.

In the study of chronobiology, entrainment occurs when rhythmic physiological or behavioral events match their period to that of an environmental oscillation. It is ultimately the interaction between circadian rhythms and the environment. A central example is the entrainment of circadian rhythms to the daily light–dark cycle, which ultimately is determined by the Earth's rotation. Exposure to certain environmental stimuli will cue a phase shift, and abrupt change in the timing of the rhythm. Entrainment helps organisms maintain an adaptive phase relationship with the environment as well as prevent drifting of a free running rhythm. This stable phase relationship achieved is thought to be the main function of entrainment.

Large milkweed bug Species of true bug

Oncopeltus fasciatus, known as the large milkweed bug, is a medium-sized hemipteran of the family Lygaeidae. It is distributed throughout North America, from Central America through Mexico and the Caribbean to southern areas in Canada. Costa Rica represents this insect's southern limit. It inhabits disturbed areas, roadsides, and open pastures. Due to this widespread geographic distribution, this insect exhibits varying life history trade-offs depending on the population location, including differences in wing length and other traits based on location.

Pain in crustaceans Ethical debate

The question of whether crustaceans experience pain is a matter of scientific debate. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.

Developmental plasticity is a general term referring to changes in neural connections during development as a result of environmental interactions as well as neural changes induced by learning. Much like neuroplasticity or brain plasticity, developmental plasticity is specific to the change in neurons and synaptic connections as a consequence of developmental processes. A child creates most of these connections from birth to early childhood.

The biopsychological theory of personality is a model of the general biological processes relevant for human psychology, behavior, and personality. The model, proposed by research psychologist Jeffrey Alan Gray in 1970, is well-supported by subsequent research and has general acceptance among professionals.

Fear-potentiated startle (FPS) is a reflexive physiological reaction to a presented stimulus, and is an indicator of the fear reaction in an organism. The FPS response can be elicited in the face of any threatening stimulus, but it can also be elicited by a neutral stimulus as a result of fear conditioning, a process that occurs when a benign stimulus comes to evoke fear and anxiety upon being paired with a traumatic or fear-provoking event. The stimulus in question is usually of auditory or visual nature, and startle response measures include eyeblink rates and pulse/heart rate. The negative impact of heightened FPS in the face of neutral stimuli can be treated pharmacologically, using psychotropic medications that are typically used to reduce anxiety in humans. Recent literature, moreover, has implicated increased FPS responses as a correlate in posttraumatic stress disorder (PTSD) and other anxiety disorders.

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In biology, constructive development refers to the hypothesis that organisms shape their own developmental trajectory by constantly responding to, and causing, changes in both their internal state and their external environment. Constructive development can be contrasted with programmed development, the hypothesis that organisms develop according to a genetic program or blueprint. The constructivist perspective is found in philosophy, most notably developmental systems theory, and in the biological and social sciences, including developmental psychobiology and key themes of the extended evolutionary synthesis. Constructive development may be important to evolution because it enables organisms to produce functional phenotypes in response to genetic or environmental perturbation, and thereby contributes to adaptation and diversification.

Human contingency learning (HCL) is the observation that people tend to acquire knowledge based on whichever outcome has the highest probability of occurring from particular stimuli. In other words, individuals gather associations between a certain behaviour and a specific consequence. It is a form of learning for many organisms.

References

  1. ↑ Binder MD, Hirokawa N, Windhorst U, eds. (2009). "Behavioral Plasticity". Encyclopedia of neuroscience. Berlin: Springer. p. 372. doi:10.1007/978-3-540-29678-2_594. ISBN   978-3-540-23735-8.
  2. ↑ Orizaola, Germán; Dahl, Emma; Laurila, Anssi (2012). "Reversibility of predator-induced plasticity and its effect at a life-history switch point". Oikos. 121 (1): 44–52. doi:10.1111/j.1600-0706.2011.19050.x. ISSN   0030-1299.
  3. ↑ Tinbergen, Niko (1951). The study of Instinct (1st ed.). Oxford University Press. ISBN   978-0-19-501371-9.
  4. ↑ Shettleworth, Sarah (2010). Cognition, Evolution and Behavior (2nd ed.). Oxford University Press. ISBN   978-0-19-531984-2.
  5. ↑ West-Ebberhard, MJ (2003). Developmental Plasticity and Evolution. Oxford University Press. ISBN   9780195122350.
  6. 1 2 3 4 5 Snell-Rood, EC (2013). "An overview of the evolutionary causes and consequences of behavioural plasticity". Animal Behaviour. 85 (5): 1004. doi:10.1016/j.anbehav.2012.12.031. S2CID   53188749.
  7. 1 2 3 4 Stamps, Judy A. (2016). "Individual differences in behavioural plasticities". Biological Reviews. 91 (2): 534–567. doi:10.1111/brv.12186. ISSN   1464-7931. PMID   25865135. S2CID   10433665.
  8. ↑ Mery, F; Burns, J (May 2010). "Behavioural plasticity: an interaction between evolution and experience". Evolutionary Ecology. 24 (3): 571–583. doi:10.1007/s10682-009-9336-y. S2CID   45562817.
  9. ↑ Andrew, N.R. (2013). "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 of Insect Physiology. 59 (9): 870–880. doi:10.1016/j.jinsphys.2013.06.003. PMID   23806604.
  10. ↑ Zhou, Y (2008). "Reaction norm variants for male calling song in populations of Achroia grisella (Lepidoptera: Pyralidae): toward a resolution of the lek paradox". Evolution. 62 (6): 1317–1334. doi: 10.1111/j.1558-5646.2008.00371.x . PMID   18346222. S2CID   17499218.
  11. ↑ Emran, B.J (2011). "Zebrafish larvae lose vision at night". Proceedings of the National Academy of Sciences of the United States of America. 107 (13): 6034–6039. doi: 10.1073/pnas.0914718107 . PMC   2851871 . PMID   20224035.
  12. ↑ Rodríguez, Rafael (2013). "The evolution and evolutionary consequences of social plasticity in mate preferences". Animal Behaviour. 85 (5): 1041–1047. doi:10.1016/j.anbehav.2013.01.006. S2CID   44163248.
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