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=                Fluid and crystallized intelligence                 =
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                            Introduction
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According to the theory published in 1971 by the psychologist Raymond
Cattell, general intelligence ('g') is subdivided into fluid
intelligence ('g'f) and crystallized intelligence ('g'c). Fluid
intelligence is the ability to  solve novel reasoning problems and is
correlated with a number of important skills such as comprehension,
problem solving, and learning. Crystallized intelligence on the other
hand is the ability to deduce secondary relational abstractions by
applying primary relational abstractions to each other. But the
deduced relations among relations must be checked by fluid
intelligence.

Fluid intelligence depends on working memory capacity, localized in
the prefrontal cortex. This region degenerates faster than other
cortical regions in the course of aging and encephalopathies. Fluid
intelligence peaks at around age 20, and then gradually declines.


                              History
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Fluid and crystallized intelligence were originally identified by
Raymond Cattell. Concepts of fluid and crystallized intelligence were
further developed by Cattell's student, John L. Horn.

Some researchers have linked the theory of fluid and crystallized
intelligences to Piaget's concept of figurative and operative
intelligences occurring during the Pre-operational stage.


                     Fluid versus crystallized
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*Fluid intelligence is inductive (visuospatial) intelligence, which is
synergetic, because its conclusions do not mechanically follow from
their premises.
*Crystallized intelligence is deductive (verbal and numeric)
intelligence, which is asynergetic, because its conclusions
mechanically follow from their premises.

Each type of crystallized intelligence is independent of the other
(increasing a student's proficiency in Latin does not increase the
student's proficiency in algebra), but to a high degree dependent on
the individual's fluid intelligence (students proficient in Latin tend
to be proficient in algebra, too, because people with a high 'g'f tend
to acquire more 'g'c-knowledge and at faster rates), and, to a lesser
degree, on the quality of the learning environment ('e.g.', the
quality of available books).


                          Factor structure
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Fluid intelligence generally correlates with measures of abstract
reasoning and puzzle solving. Crystallized intelligence correlates
with abilities that depend on knowledge and experience, such as
vocabulary, general information, and analogies. Paul Kline identified
a number of factors that shared a correlation of at least r=.60 with
Gf and Gc. Factors with  of greater than 0.6 on Gf included induction,
visualization, quantitative reasoning, and ideational fluency. Factors
with median loadings of greater than 0.6 on Gc included verbal
ability, language development, reading comprehension, sequential
reasoning, and general information. It may be suggested that tests of
intelligence may not be able to truly reflect levels of fluid
intelligence. Some authors have suggested that unless an individual
was truly interested in the problem presented, the cognitive work
required may not be performed because of a lack of interest.  These
authors contend that a low score on tests which are intended to
measure fluid intelligence may reflect more a lack of interest in the
tasks rather than inability to complete the tasks successfully.


                 Measurement of fluid intelligence
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There are various measures that assess fluid intelligence. The Cattell
Culture Fair IQ test, the Raven Progressive Matrices (RPM), and the
performance subscale of the WAIS are measures of Gf. The RPM is one of
the most commonly used measures of fluid abilities. It is a non-verbal
multiple choice test. Participants have to complete a series of
drawings by identifying relevant features based on the spatial
organization of an array of objects, and choosing one object that
matches one or more of the identified features. This task assesses the
ability to consider one or more relationships between mental
representations or 'relational reasoning.' 'Propositional analogies'
and semantic decision tasks are also used to assess relational
reasoning.

Standardized IQ tests such as those used in psychoeducational
assessment also include tests of fluid intelligence. In the
Woodcock-Johnson Tests of Cognitive Abilities, Gf is assessed by two
tests: Concept Formation (Test 5) in the Standard Battery and Analysis
Synthesis (Test 15) in the Extended Battery. On Concept Formation
tasks, the individual has to apply concepts by inferring the
underlying "rules" for solving visual puzzles that are presented in
increasing levels of difficulty. Individuals at the preschool level
have to point to a shape that is different from others in a set. As
the level of difficulty increases, individuals increasingly
demonstrate an understanding of what constitutes a key difference (or
the "rule") for solving puzzles involving one to one comparisons, and
on later items identifying common differences among a set of items.
For more difficult items, individuals need to understand the concept
of "and" (e.g. solution must have some of this and some of that) and
the concept of "or" (e.g. to be inside a box, the item must be either
this or that). The most difficult items require fluid transformations
and cognitive shifting between the various types of concept puzzles
that the examinee has worked with previously.

Concept Formation tasks assess inductive reasoning ability. In the
Analysis-Synthesis test, the individual has to learn and orally state
the solutions to incomplete logic puzzles that mimic a miniature
mathematics system. The test also contains some of the features
involved in using symbolic formulations in other fields such as
chemistry and logic. The individual is presented with a set of logic
rules, a "key" that is used to solve the puzzles. The individual has
to determine the missing colors within each of the puzzles using the
key. Complex items present puzzles that require two or more sequential
mental manipulations of the key to derive a final solution.
Increasingly difficult items involve a mix of puzzles that require
fluid shifts in deduction, logic, and inference. Analysis Synthesis
tasks assess general sequential reasoning.

In the Wechsler Intelligence Scale for Children-IV (WISC IV), the
Perceptual Reasoning Index contains two subtests that assess Gf:
Matrix Reasoning, which involves induction and deduction, and Picture
Concepts, which involves induction. In the Picture Concepts task,
children are presented a series of pictures on two or three rows and
asked which pictures (one from each row) belong together based on some
common characteristic. This task assesses the child's ability to
discover the underlying characteristic (e.g. rule, concept, trend,
class membership) that governs a set of materials. Matrix Reasoning
also tests this ability as well as the ability to start with stated
rules, premises, or conditions and to engage in one or more steps to
reach a solution to a novel problem (deduction). In the Matrix
Reasoning test, children are presented a series or sequence of
pictures with one picture missing. Their task is to choose the picture
that fits the series or sequence from an array of five options. Since
Matrix Reasoning and Picture Concepts involve the use of visual
stimuli and do not require expressive language, they are considered to
be non-verbal tests of Gf.

Within the corporate environment, fluid intelligence is a predictor of
a person's capacity to work well in environments characterised by
complexity, uncertainty, and ambiguity. The Cognitive Process Profile
(CPP) measures  a person's fluid intelligence and cognitive processes.
It maps these against suitable work environments according to Elliott
Jacques Stratified Systems Theory.


                     Development and physiology
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Fluid intelligence, like reaction time, typically peaks in young
adulthood and then steadily declines. This decline may be related to
local atrophy of the brain in the right cerebellum. Other researchers
have suggested that a lack of practice, along with age-related changes
in the brain may contribute to the decline. Crystallized intelligence
typically increases gradually, stays relatively stable across most of
adulthood, and then begins to decline after age 65. The exact peak age
of cognitive skills remains elusive, depending on the skill
measurement as well as on the survey design. Cross-sectional data
shows typically an earlier onset of cognitive decline in comparison
with longitudinal data. The former may be confounded due to cohort
effects while the latter may be biased due to prior test experiences.

Working memory capacity is closely related to fluid intelligence, and
has been proposed to account for individual differences in Gf.


    Improving fluid intelligence with training on working memory
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According to David Geary, Gf and Gc can be traced to two separate
brain systems. Fluid intelligence involves both the dorsolateral
prefrontal cortex, the anterior cingulate cortex, and other systems
related to attention and short-term memory. Crystallized intelligence
appears to be a function of brain regions that involve the storage and
usage of long-term memories, such as the hippocampus.

Some researchers question whether the results of training are long
lasting and transferable, especially when these techniques are used by
healthy children and adults without cognitive deficiencies. A
meta-analytical review conducted by researchers from the University of
Oslo in 2012 concluded that "memory training programs appear to
produce short-term, specific training effects that do not generalize."

In a study using four individual experiments, 70 participants (36 of
them female, all with a mean age of 25.6) recruited from the
University of Bern community, Susanne M. Jaeggi and her colleagues at
the University of Michigan found that healthy young adults who
practiced a demanding working memory task (dual n-back, a task that
has strong face validity, has received some criticism regarding its
construct validity and is in widespread use as a measure of working
memory) approximately 25 minutes per day for between 8 and 19 days had
statistically significant increases in their scores on a matrix test
of fluid intelligence taken before and after the training than a
control group who did not do any training at all.

A further examination of these findings was published in 2008 in the
Proceedings of the Nation Academy of Sciences of the United States of
America. Summarizing findings in the study as evidence that
demonstrates that "fluid intelligence is trainable to a significant
and meaningful degree."

Attention is drawn to the limitations of these results and the need
for specific follow up inquiry. Robert J. Sternberg comments that "it
is unclear to what extent the results can be generalized to other
working-memory tasks" and  states "it would be useful to show that the
training transfers to success in meaningful behaviours that extend
beyond the realm of psychometric testing". Sternberg asserts that
ability level of the test participants is not necessarily examining a
wide range of ability levels, or "address whether the training is
durable over extended periods of time [and not only] "fleeting."

A second study conducted at the University of Technology in Hangzhou,
China, supports Jaeggi's results independently. After student subjects
were given a 10-day training regimen based on the dual n-back working
memory theory, the students were tested on Raven's Standard
Progressive Matrices. Their scores were found to have increased
significantly.

Subsequent studies on n-back, namely by Chooi & Thompson and
Redick et al., do not support the findings of the Jaeggi study.
Although participants' performance on the training task improved,
these studies showed no significant improvement in the mental
abilities tested, especially fluid intelligence and working memory
capacity.


                              See also
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*21st century skills
*CHC theory
*Deeper learning
*General intelligence factor
*Intelligence
*Three stratum theory
*Malleability of intelligence
*Nootropic
*Outline of human intelligence
*Raymond Cattell
*Spatial intelligence (psychology)


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