Table 1.
Summary of the associations between temporal discounting and socio-demographic, psychological, neuroimaging, and molecular genetic variables.
| Variables | Direction of association | Effect sizes |
|---|---|---|
| SOCIO-DEMOGRAPHIC VARIABLES | ||
| Age | No association, Positive, Negative | Moderate |
| Gender | No association, Men discount more | Moderate |
| Education level | Negative | Moderate |
| Income | Negative | Moderate |
| Marital status | Singles discount more | Moderate |
| Limitations: Small sample sizes, low-powered studies, the correlation between socio-demographic variables and temporal discounting is prone to misinterpretations and should be considered together with other biological and psychological variables | ||
| PSYCHOLOGICAL VARIABLES | ||
| Personality | ||
| Big Five | ||
| Openness | Negative | Low |
| Extraversion | Positive | Low |
| Conscientiousness | Negative | Low |
| Neuroticism | Positive | Low |
| Agreeableness | No association | |
| Trait impulsivity | Positive | Low to moderate |
| Future oriented cognitive styles and imagery | ||
| Ability to imagine (present, future) | Positive | Moderate to high |
| Future orientation | Negative | Low to moderate |
| Intelligence | Negative | Moderate |
| Inhibitory control | No association, Negative | Low to high |
| Limitations: Small sample sizes, low correlations, interaction effects are often not considered, effect of possible mediator and moderator variables not sufficiently explored (e.g., the role of risk preferences), impact of task specificities on the obtained results | ||
| NEUROIMAGING | ||
| Brain structure | ||
| Gray matter volume of regions associated with valuation (vmPFC, striatum, PCC, OFC) | Positive, Negative | Low to moderate |
| Gray and white matter volume of regions associated with cognitive control (dlPFC, FP) | Positive, Negative | Low to high |
| White matter volume and cortical thickness of regions associated with memory and future oriented thinking (hippocampus/parahippocampus, entorhinal cortex) | Positive, Negative | Low to high |
| Connectivity strength of (inhibitory) corticostriatal tracts | Negative | Moderate to high |
| Brain function | ||
| Neural sensitivity to rewards and delays (vmPFC, vS, OFC, dlPFC) | Positive, Negative | Low to high |
| Recruitment of PFC regions during reward anticipation, valuation, and choice | Negative | Not reported |
| Intrinsic connectivity strength between cortical regions associated with cognitive control and valuation (e.g., FP and vmPFC) | Negative | Low to moderate |
| Task-related functional connectivity between cortical and subcortical (e.g., dlPFC and striatum), cortical and limbic (e.g., ACC and hippocampus), and within cortical areas (e.g., dlPFC and vmPFC) | Negative | Not reported |
| Limitations: Low-powered studies, small sample sizes, inconsistent and non-replicated findings, moderator and mediator variables not thoroughly considered, dependence of the results on the methodology | ||
| MOLECULAR GENETICS | ||
| Genetic variations in the dopaminergic systems associated with DA hypofunction | No associations, Positive | Low to moderate |
| Single nucleotide polymorphism rs6528024 on the X chromosome (associated with internalization of a serotonin receptor) | No associations, Negative | Low |
| Minor allele of r13395777 (intergenic region) on chromosome 2 | No associations, Positive | Low |
| Limitations: Low-powered studies, non-replicated findings, task impurity problem, no studies on environment × gene interactions | ||
Low effect sizes are considered d (or r) < 0.15; moderate effect sizes are considered 0.15 ≤ d (or r) ≤ 0.35; high effect sizes are considered d (or r) > 0.35. vmPFC, ventromedial prefrontal cortex; PCC, posterior cingulate cortex; OFC, orbitofrontal cortex; dlPFC, dorsolateral prefrontal cortex; FP, frontal pole; vS, ventral striatum; ACC, anterior cingulate cortex; DA, dopamine.