This section will have content posted to it in subsequent revisions of this chapter (Curiosity Personality Spectrum Tapestry). The current version as of this writing is v #1.0.

Researchers discover the first-ever link between intelligence and curiosity

Neuronal calcium sensor-1 (NCS-1) - Known to affect the memory of worms. Linked to bipolar and schizophrenia in humans.

When increased by 1.5 fold specifically in the dentate gyrus of mouse models, increased the ability of brain cells to change how they communicate with each other, gave the mice superior memory in complex tasks. Significantly increased in exploratory behavior (curiosity).

Both curiosity and spatial memory impaired when a benign drug (developed at Mount Sinai) blocked the NCS-1 protein from binding to the dopamine type-2 receptors (a major target of anti-psychotics) in the dentate gyrus.

NCS-1 regulates synaptic transmission, helps control the dynamics of nerve terminal growth, is critical for some forms of learning and memory in C. elegans and mammals, regulates corticohippocampal plasticity. Enhancing levels of NCS-1 in the mouse dentate gyrus increases spontaneous exploration of safe environments (above), potentially linking NCS-1 to curiosity.

The expression of NCS-1 increases in bipolar disorder and some forms of schizophrenia. NCS-1 has also been linked with Autism. In addition NCS-1 is significant in intelligence in creating curiosity by its function on dopamine D2 receptors in the dentate gyrus (above), increasing memory for complex tasks.

"Personality-Gene" makes songbirds curious

Dopamine receptor D₄ (DRD4) carries the building instructions for a receptor in the brain, which forms the docking station for the neurotransmitter dopamine. Birds with a specific variant of this dopamine receptor D4 gene show a stronger exploratory behavior than individuals with other variants

It is linked to many neurological and psychiatric conditions including schizophrenia and bipolar disorder, ADHD, addictive behaviors, Parkinson's disease, and eating disorders such as anorexia nervosa.

Mutations in this gene have been associated with various behavioral phenotypes, including autonomic nervous system dysfunction, attention deficit/hyperactivity disorder, schizophrenia, and the personality trait of novelty seeking.

It is important to note the individual's age with novelty seeking. This behavior will decrease with time, especially as the brains of adolescents and young adults finalize in development. Possible factors of variation include gender, ethnicity, temperament and environment.

In addition to potential heredity, novelty seeking (NS) behaviors are seen with the modulation of dopamine. The overall effect of dopamine when exposed to a novel stimuli is a mass release of the neurotransmitter in reward systems of the brain including the mesolimbic pathway. The mesolimbic pathway is active in every type of addiction and is involved with reinforcement. Because of this activation in the brain, NS has been linked to personality disorders as well as substance abuse and other addictive behaviors. DRD4 receptors are highly expressed in areas of the limbic system associated with emotion and cognition.

The 48-base pair variable number tandem repeat (VNTR) in exon 3 range from 2 to 11 repeats.

DRD4-7R, the 7-repeat (7R) variant of DRD4, has been linked to a susceptibility for developing ADHD in several meta-analyses and other psychological traits and disorders.

The frequency of the alleles varies greatly between populations, e.g., the 7-repeat version has high incidence in America and low in Asia. "Long" versions of polymorphisms are the alleles with 6 to 10 repeats. 7R appears to react less strongly to dopamine molecules.

The 48-base pair VNTR has been the subject of much speculation about its evolution and role in human behaviors cross-culturally. The 7R allele appears to have been selected for about 40,000 years ago. In 1999 Chen and colleagues observed that populations who migrated farther in the past 30,000 to 1,000 years ago had a higher frequency of 7R/long alleles. They also showed that nomadic populations had higher frequencies of 7R alleles than sedentary ones. More recently it was observed that the health status of nomadic Ariaal men was higher if they had 7R alleles. However, in recently sedentary (non-nomadic) Ariaal those with 7R alleles seemed to have slightly deteriorated health.

Despite early findings (above) of an association between the DRD4 48bp VNTR and novelty seeking (a normal characteristic of exploratory and excitable people), a 2008 meta-analysis compared 36 published studies of novelty seeking and the polymorphism and found no effect. The meta-analysis of 11 studies did find that another polymorphism in the gene, the C-521T, showed an association with novelty seeking. While human results are controversial, an increasing body of animal evidence has linked DRD4 variants with novelty seeking, and new evidence suggests that human encroachment may exert selection pressure in favor of DRD4 variants associated with novelty seeking.

Novelty-seeking behavior is probably mediated by several genes, and the variance attributable to DRD4 by itself is not particularly large.

Association of the Dopamine D4 Receptor (DRD4) Gene and
Approach-Related Personality Traits: Meta-Analysis and New Data

Initial meta-analysis supported the association of the DRD4 C-521T polymorphism, but not the VNTR polymorphism, with approach-related traits. This conclusion was qualified by evidence of significant publication bias and the failure to detect association in a replication sample comprising individuals at the extremes of the trait distribution. The association of the C-521T polymorphism observed in our initial meta-analysis was robust to the inclusion of these new data, but our revised meta-analysis indicated that the association was present for measures of novelty seeking and impulsivity but not for measures of extraversion.

The DRD4 gene may be associated with measures of novelty seeking and impulsivity but not extraversion. The association of the C-521T variant with these measures, if genuine, may account for up to 3% of phenotypic variance.

→ The Multiple Filters in Play section was last updated 13 Nov 2017 22:00 PST ←

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