Here's the abstract of a new study in the Mankind Quarterly reporting quite rapid increases in raw IQ test scores of about 18 points over 25 years:
Generational Change of Cognitive Test Performance in Dominica
Gerhard Meisenberg, Elliott Lawless, Eleonor Lambert and Anne Newton
Mental ability, as assessed by standardized tests, is not fixed in time. Large IQ gains have been recorded in many industrialized countries during the 20th century, but very little is known about IQ trends in the less developed countries. The present study investigates generational changes in mental test performance on the Caribbean island of Dominica. In a cross-sectional design, Raven's Standard Progressive Matrices were administered to two age groups: young adults between the ages of 18 and 25 years, and older adults between the ages of 51 and 62 years. Raw scores were 23.3 ± 11.4 points for the older generation and 36.1 ± 10.9 points for the younger generation. Compared to the current British norms for their respective age groups, the average IQs of these two cohorts were estimated as 61 and 73, respectively. Since the age-specific British norms reflect a rising IQ trend in Britain already, the real gain in Dominica is not 12 points but approximately 17 to 19 points. The results on a vocabulary test suggest similar cohort gains in word knowledge. Differences between the Afro-Caribbean majority and the native Caribs were small. Data are presented to show that the difference between the two age groups represents a cohort effect rather than an aging effect. The implications of the Flynn effect for economic development and cultural evolution are discussed.
Typically, the rare published reports on the size of the Flynn Effect in 3rd World countries fail to mention the actual IQ scores, so this one reporting a rise from 61 to about 79 over one generation is particularly interesting.