Cognitive abilities and the rate of their extinction with age are shown to be determined to a significant extent by genetic factors. The serotoninergic system of the brain affects the development and plastic rearrangements of the brain, and plays an important role in learning and memory processes. Links found between the activity of the serotonin transporter gene and the efficiency of memory processes provided grounds for studying associations between the efficiency of memory and the STin2VNTR polymorphism, which results from a change in the number of tandem repeats in intron 2, which has two frequent alleles (10 and 12 repeats) and one rare (nine repeats) allele. This polymorphism fulfils the role of an allele-dependent amplifier of gene expression. The studies involved younger (n = 204: 84 men and 120 women, age 19–35 years) and older (n = 129: 57 men and 72 women, age over 55 years) right-handed subjects. The efficiency of verbal memory was determined in terms of reproduction of words heard with the right and left ears in a dichotic test procedure and in terms of a measure of the recognition, among distractors, of syllables previously displayed on a screen; imaginal memory efficiency was tested in terms of shape recognition. Regardless of other factors, carriers of the 12/12 genotype of the STin2VNTR polymorphism, as compared with carriers of the 10 allele, demonstrated significantly better memorization of dichotically presented words and imaginal memory. For imaginal memory, the genotype effect was more marked in the older age group.