Malleability Of Intelligence
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Malleability of intelligence describes the processes by which
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
can increase or decrease over time and is not static. These changes may come as a result of
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
,
pharmacological Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
factors,
psychological Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between t ...
factors,
behavior Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as wel ...
, or environmental conditions. Malleable intelligence may refer to changes in cognitive skills,
memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
,
reasoning Reason is the capacity of consciously applying logic by drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activities as philosophy, science, lang ...
, or
muscle memory Muscle memory is a form of procedural memory that involves consolidating a specific motor task into memory through repetition, which has been used synonymously with motor learning. When a movement is repeated over time, the brain creates a long-t ...
related
motor skills A motor skill is a function that involves specific movements of the body's muscles to perform a certain task. These tasks could include walking, running, or riding a bike. In order to perform this skill, the body's nervous system, muscles, and br ...
. In general, the majority of changes in human intelligence occur at either the onset of development, during the
critical period In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If, for some reason, the org ...
, or during old age (see
Neuroplasticity Neuroplasticity, also known as neural plasticity, or brain plasticity, is the ability of Neural circuit, neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that diffe ...
).
Charles Spearman Charles Edward Spearman, FRS (10 September 1863 – 17 September 1945) was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient. He also did seminal work on mod ...
, who coined the
general intelligence factor The ''g'' factor (also known as general intelligence, general mental ability or general intelligence factor) is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarizes ...
"g", described intelligence as one's ability to adapt to his environment with a set of useful skills including reasoning and understanding patterns and relationships. He believed individuals highly developed in one intellectual ability tended to be highly developed at other intellectual abilities. A more intelligent individual was thought to be able to more easily "accommodate" experiences into existing cognitive structures to develop structures more compatible with environmental stimuli.Garlick, D. (2002). Understanding the nature of the general factor of intelligence: The role of individual differences in neural plasticity as an explanatory mechanism. eview Psychological Review, 109(1), 116–136. In general, intelligence is thought to be attributed to both genetic and environmental factors, but the extent to which each plays a key role is highly disputed. Studies of identical and non-identical twins raised separately and together show a strong correlation between child IQ and socio-economic level of the parents. Children raised in lower-class families tend to score lower on intelligence tests when compared to children raised in both middle and upper-class families. However, there is no difference in intelligence scores between children raised in middle versus upper-class families.


Definitions

*
Intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
: a very general capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience.Deary, I. J., Penke, L., & Johnson, W. (2010). The neuroscience of human intelligence differences. eview Nature Reviews Neuroscience, 11(3), 201–211. *
Critical period In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If, for some reason, the org ...
: a restricted developmental period during which the nervous system is particularly sensitive to the effects of experience .


Neuroscience basis

The biological basis of
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
is founded in the degree of connectivity of
neurons A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
in the brain and the varying amounts of
white White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...
and
grey Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
matter. Studies show that intelligence is positively correlated with total cerebral volume. While it is true that the number of neurons in the brain actually decreases throughout development, as neural connections grow and the pathways become more efficient, the supporting structures in the brain increase. This increase in supporting tissues, which include
myelination Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be l ...
,
blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
, and
glial cells Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form myel ...
, leads to an increase in overall brain size. When brain circumference and IQ were compared in 9 year olds, a positive correlation was found between the two. An increase of 2.87 IQ points occurred for each
standard deviation In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while ...
increase in brain
circumference In geometry, the circumference (from Latin ''circumferens'', meaning "carrying around") is the perimeter of a circle or ellipse. That is, the circumference would be the arc length of the circle, as if it were opened up and straightened out to ...
.Gale, C. R., O'Callaghan, F. J., Godfrey, K. M., Law, C. M., & Martyn, C. N. (2004). Critical periods of brain growth and cognitive function in children. rticle Brain, 127, 321–329.


Importance of critical period

The brain grows rapidly for the first five years of human development. At age five, the human brain is 90% of its total size. Then the brain finishes growing gradually until mid to late twenties. From start to finish, the brain increases in size by over 300% from birth.Linden, D. J. (2007). The Accidental Mind: How Brain Evolution Has Given Us Love, Memory, Dreams, and God. Cambridge: The Belknap Press of Harvard University Press. The
critical period In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If, for some reason, the org ...
, defined as the beginning years of brain development, is essential to intellectual development, as the brain optimizes the overproduction of
synapses In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...
present at birth. During the
critical period In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If, for some reason, the org ...
, the neuronal pathways are refined based on which synapses are active and receiving transmission. It is a "use it or lose it" phenomenon.


Neural plasticity

Neural plasticity Neuroplasticity, also known as neural plasticity, or brain plasticity, is the ability of neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that differs from how it p ...
refers to any change in the structure of the neural network that forms the central nervous system. Neural plasticity is the neuronal basis for changes in how the mind works, including learning, the formation of memory, and changes in intelligence. One well-studied form of plasticity is
Long-Term Potentiation In neuroscience, long-term potentiation (LTP) is a persistent strengthening of synapses based on recent patterns of activity. These are patterns of synaptic activity that produce a long-lasting increase in signal transmission between two neurons ...
(LTP). It refers to a change in neural connectivity as a result of high activation on both sides of a synaptic cleft. This change in neural connectivity allows information to be more easily processed, as the neural connection associated with that information becomes stronger through LTP. Other forms of plasticity involve the growth of new neurons, the growth of new connections between neurons, and the selective elimination of such connection, called "dendritic pruning".


Genetic factors of intelligence

Humans have varying degrees of
neuroplasticity Neuroplasticity, also known as neural plasticity, or brain plasticity, is the ability of Neural circuit, neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that diffe ...
due to their genetic makeups, which affects their ability to adapt to conditions in their environments and effectively learn from experiences. The degree to which intelligence test scores can be linked to genetic
heritability Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of h ...
''increases'' with age. There is presently no explanation for this puzzling result, but flaws in the testing methods are suspected. A study of Dutch twins concludes that intelligence of 5 year olds is 26%
heritable Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic informa ...
, while the test scores of 12-year-olds is 64%
heritable Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic informa ...
. Structurally, genetic influences explain 77–88% of the variance in the thickness of the mid-sagittal area of the
corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...
, the volume of the
caudate nucleus The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia in the human brain. While the caudate nucleus has long been associated with motor processes due to its role in Parkinson's di ...
, and the volumes of the parietal and temporal lobes.


Pharmacological influence

Numerous
pharmacological Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
developments have been made to help organize neural circuitry for patients with learning disorders. The
cholinergic Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word "choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation. F ...
and
glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/ aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonist ...
systems in the brain serve an important role in learning, memory, and the developmental organization of neuronal circuitry. These systems help to capitalize on the critical period and organize
synaptic transmission Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron), ...
.
Autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
and other learning disabilities have been targeted with drugs focusing on cholinergic and glutamatergic transmission. These drugs increase the amount of
acetylcholine Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
present in the brain by increasing the production of acetylcholine precursors, as well as inhibiting acetylcholine degradation by cholinesterases. By focusing on heightening the activity of this system, the brain's responsiveness to
activity-dependent plasticity Activity-dependent plasticity is a form of functional and structural neuroplasticity that arises from the use of cognitive functions and personal experience; hence, it is the biological basis for learning and the formation of new memories. Activity- ...
is improved. Specifically, glutamatergic drugs may reduce the threshold for
LTP LTP may refer to: Biology and medicine * Lateral tibial plateau, part of a leg bone * Lipid transfer proteins, proteins found in plant tissues * Long-term potentiation (neurophysiology), a long-lasting enhancement in signal transmission between ...
, promote more normal
dendritic spine A dendritic spine (or spine) is a small membranous protrusion from a neuron's dendrite that typically receives input from a single axon at the synapse. Dendritic spines serve as a storage site for synaptic strength and help transmit electrical si ...
morphology, and retain a greater number of useful synaptic connections. Cholinergic drugs may reconnect the
basal forebrain Part of the human brain, the basal forebrain structures are located in the forebrain to the front of and below the striatum. They include the ventral basal ganglia (including nucleus accumbens and ventral pallidum), nucleus basalis, diagonal band ...
with the
cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...
and
hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, a ...
, connections that are often disrupted in patients with learning disorders.


Psychological factors

Psychological Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between t ...
factors and preconceived notions about intelligence can be as influential on intelligence as genetic makeup. Children with early
chronic stress Chronic stress is the physiological or psychological response induced by a long-term internal or external stressor. The stressor, either physically present or recollected, will produce the same effect and trigger a chronic stress response. There is ...
show impaired corticolimbic connectivity in development. Early chronic stress is defined as inconsistent or inadequate care-giving and disruption to early rearing environment. These children showed decreased
cognitive function Cognitive skills, also called cognitive functions, cognitive abilities or cognitive capacities, are brain-based skills which are needed in acquisition of knowledge, manipulation of information and reasoning. They have more to do with the mechanisms ...
, especially in fluid
cognition Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...
, or the ability to effectively utilize
working memory Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...
. The lack of connectivity between the
limbic system The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.Schacter, Daniel L. 2012. ''Ps ...
and the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46, ...
can be blamed for this deficiency.Blair, C. (2006). How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as an aspect of human cognitive ability. eview Behavioral and Brain Sciences, 29(2), 109–160.


Behavioral factors

In the study of malleable intelligence, behavioral factors are often the most intriguing because these are factors humans can seek to control. There are numerous behavioral factors that affect intellectual development and
neural plasticity Neuroplasticity, also known as neural plasticity, or brain plasticity, is the ability of neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that differs from how it p ...
. The key is plasticity, which is caused by experience-driven electrical activation of
neurons A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
. This experience-driven activation causes
axons An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, th ...
to sprout new branches and develop new presynaptic terminals. These new branches often lead to greater mental processing in different areas.


Taking advantage of the critical period

As previously discussed, the
critical period In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If, for some reason, the org ...
is a time of neural pruning and great intellectual development.


See also

* * * * *


References


External links


The Entity Theory of Intelligence
– ''Parenting Science''
Raising Our I.Q.
– ''NY Times'' {{DEFAULTSORT:Malleable Intelligence Neuroscience Intelligence Cognitive science