Regional intelligence and suicide rate: new data for Australia and a synthesis of research

Previous research has shown for the most part positive correlations between intelligence and suicide prevalence on the national level. However, this study found proxies for regional intelligence in Australia (international average domain scores from the PISA 2000 study) to be significantly negatively correlated with the total, male, and female suicide rates of the different administrative divisions of Australia, and this finding was independent of regional wealth. A research synthesis of the current results and those from similar studies of other countries (positive correlations for Austria, Belarus, The British Isles, Denmark, and The Netherlands; inconclusive findings for France, Germany, and the USA) was conducted. This synthesis of research findings showed that positive ecological correlations of intelligence with suicide rate were more likely observed for nations with higher suicide rates and poorer general living conditions, whereas there was no relation with national IQ.     

Evidence for a positive ecological correlation of regional intelligence and suicide mortality in the United States during the early 20th century

Several contemporary cross-national and intranational geographic studies have reported positive ecological (group-level) associations of intelligence and suicide mortality. These findings are consistent with facts from suicide research and with an evolutionary view of suicidal behavior. The present research extended these accounts cross-temporally. Analysis of E. L. Thorndike's state-level personal quality scores and standardized birth rates of eminent persons, taken as proxy variables for regional intelligence, along with historical state suicide rates (1913-1924 and 1928-1932) showed that intelligence and suicide mortality across the U.S.A. were already clearly positively related during the early 20th century, suggesting time stability of the effect. Within the U.S.A., the effect is possibly due to state differences in the ethnic composition, which correspond to both suicide rates and intelligence proxies. It is argued that the most parsimonious interpretation of these ecological findings remains that they indeed reflect individual-level effects, that a positive link between intelligence and suicide is entirely compatible with positive overall links between intelligence and health and longevity, and that the ultimate explanative background for the positive link between intelligence and suicide may be provided through the framework of Rushton's differential K theory.     

Suicide and Firearm Prevalence: Are Youth Disproportionately Affected?

The effect of firearm availability on suicide may differ among age groups. We used regression analysis to examine the relationship between suicide rates and household firearm ownership for four age groups in the nine census regions from 1979 to 1994, adjusting for regional divorce rates, education, unemployment, and urbanicity. Results showed that firearm ownership levels are correlated with suicide rates among 15- to 24-year-olds and 65- to 84-year-olds, but not among 25-to 64-year-olds. The findings suggest that if the relationship is causal, a 10% fall in regional firearm ownership levels would lead to a 3.0% decrease in suicide rates.     

State IQ and suicide rates in the United States

Previous findings pertaining to the direction (positive or negative) of the ecological correlation between intelligence and suicide rates in the USA have been conflicting. Using novel state IQ estimates, derived from the Scholastic Assessment Test, the American College Test, these tests combined, or the National Assessment of Educational Progress state scores, these estimates were not consistently associated to state suicide rates. Whereas ACT-derived state IQ was significantly positively correlated with suicide rates, the correlation with composite ACT-SAT-derived state IQ was significantly negative and with both SAT-derived and NAEP-derived state IQ also negative but not significant. Validity checks pointed to possible methodological problems with the state IQ estimates. Currently available estimates of state IQ, therefore, seem not appropriate to resolve the question of the direction of the ecological correlation of intelligence and suicide mortality across the USA.     

Regional intelligence and suicide rate in Germany

Regional intelligence proxies (intranational average domain scores from the PISA 2000 and 2003 studies) were not reliably associated with the suicide rate across the states of Germany, thereby not replicating findings of a positive ecological correlation of regional intelligence and suicide prevalence from other within-nation studies (Austria, Belarus, the British Isles, Denmark, The Netherlands, and the USA).     

Youth suicide: insights from 5 years of Arizona Child Fatality Review Team data

Data on 153 youth suicides in Arizona (1994-1999) were used to explore demographic, behavioral, and experiential factors that distinguish between firearm suicide and suicide by other means. In bivariate analyses, White youths were more likely than non-White youths to use a firearm to commit suicide as were youths who had not experienced a life crisis or expressed suicidal thoughts in the past, relationships that hold in multivariate analyses at the p < 0.2 level. Targeted suicide prevention activities should supplement interventions focused on restricting access to highly lethal means of suicide such as firearms.     

Educational attainment, intelligence, interstate migration, and suicide rates in the United States: rejoinder to Abel and Kruger (2005)

Abel and Kruger (2005) reported a negative association of educational attainment and suicide rate across the United States. Given strong links between intelligence and educational attainment, this appears to be inconsistent with positive associations of intelligence and suicide rate reported in several other geographical studies. However, the apparent inconsistencies may reflect interstate migration within the U.S. adult population. Testing this hypothesis showed that interstate migration was more strongly related to state suicide rates than educational attainment. Thus, the different results obtained by Abel and Kruger could reflect migration effects, which for the U.S. might render adult-age indicators of educational attainment inappropriate to reflect regional variation in intelligence by place of birth.     

Regional intelligence and suicide rate in Denmark

Consistent with evidence from several recent geographical (cross-national and within-nation) studies (by Lester and by Voracek), a positive ecological (aggregate-level) correlation of regional intelligence and suicide rate was found across the seven major geographical regions of Denmark.     

The Getting of Wisdom: Fluid Intelligence Does Not Drive Knowledge Acquisition

The investment hypothesis proposes that fluid intelligence drives the accumulation of crystallized intelligence, such that crystallized intelligence increases more substantially in individuals with high rather than low fluid intelligence. However, most investigations have been conducted on adolescent cohorts or in two-wave data sets. There are few longitudinal representative studies with which to observe the growth of intelligence in young adulthood. A large community representative sample of 20- to 24-year-olds was recruited in 1999 and followed in 2003 and 2007. The Spot-the-Word Test Version A, a lexical decision task, was used to assess crystallized intelligence. The Symbol–Digit Modalities Test, a test of perceptual speed, was used as a measure of fluid intelligence. Latent growth models were used to examine whether growth in fluid intelligence drives the acquisition of crystallized intelligence. Fluid and crystallized intelligence are coupled; crystallized intelligence accrues in the 20s, but the rate of increase of crystallized intelligence is not associated with the level of fluid intelligence. Although young adulthood is associated with “the getting of wisdom,” accelerated development of crystallized intelligence in those with high fluid intelligence was not observed. Hence, no support was found for the investment hypothesis.     

National differences in intelligence and population rates of suicidal ideation, suicide plans, and attempted suicide

Population rates of suicidal ideation, suicide plans or attempted suicide from three independent multinational epidemiological surveys (the WHO/EURO and WHO SUPRE-MISS studies and a third one) were not significantly associated with national IQ figures. This result conflicts with previous evidence from cross-national studies (by Lester and by Voracek) of a positive ecological correlation between level of national intelligence and rates of completed suicide. Across nations, the indicators for the prevalence of suicidal behavior also lacked close correspondence with suicide rates, which may be due to the higher unreliability of assessing covert suicidal behavior (suicide ideas, thoughts, plans, and, to a lesser extent, also suicide attempts) as compared to suicidal behavior that is indisputably overt (completed suicide). Several alternative explanations for the current nil findings are also discussed.     

A revalidation of the Thurstone Test of Mental Alertness as a brief measure of intelligence through comparison with the Wechsler Adult Intelligence Scale-III

In earlier research, Rossini, Wygonik, Barrett, and Friedman (1994) demonstrated that the Thurstone Test of Mental Alertness (TMA) is a valid, brief measure of intelligence by comparing it to the Wechsler Scale of Adult Intelligence-Revised, which was at that time the "gold standard" of IQ assessment. Since that study, the WAIS has again been revised and reissued in a third edition, the WAIS-III. We assessed the relationship between scores on the Thurstone Test of Mental Alertness and this latest WAIS test to see if there is still a predictive relationship between the two tests. Correlations between the two tests and the accuracy of TMA point estimates of IQ indicate that the Thurstone Test of Mental Alertness remains a viable brief measure of adult intelligence.     

Tobacco and alcohol tax relationships with suicide in Switzerland

Previous research has shown an empirical link between tobacco and alcohol use and suicide. If tobacco and alcohol use contribute to suicidal behaviors, then policies designed to reduce the tobacco and alcohol consumption may succeed in reducing suicides as well. To test this hypothesis, correlations for suicide rates with alcohol consumption, taxes on alcohol and tobacco in Switzerland were examined using sets of time-series data from Switzerland in 1965-1994. The tax on tobacco correlated significantly negatively with male standardized suicide rate. The tax on alcohol also correlated significantly with male standardized suicide rate in an autoregressive model. On the other hand, significant relationships with female suicide rate were not found. Policies designed to reduce tobacco consumption are consistent with a benefit of reducing suicides, particularly for men in this sample.     

Cross-national social ecology of intelligence and suicide prevalence: integration, refinement, and update of studies

This study integrates, refines, and updates previous findings pertaining to positive ecologic (population-level) associations between intelligence and suicide prevalence across nations by using corrected and revised national IQ estimates and, further, a quality-of-human-conditions index, both recently published by Lynn and Vanhanen. Across a global 85-nation sample of sex-specific total suicide rates and a Eurasian 48-nation sample of sex-specific elderly suicide rates, these were positively associated with updated national IQ estimates. The associations were stronger for the general population than for elderly persons, independent of the quality of human conditions, and notedly stronger in exponential fitting of suicide rates with national IQ than in linear fitting, thereby indicating that shifts or differences in national IQ correspond to proportional, not absolute, changes in suicide rates. Implications of these findings and the question of generalizability of such associations to the individual level are discussed.     

Explaining the gender difference in self-reported suicide attempts: a nationally representative study of Norwegian adolescents

Predictors of self-reported suicide attempts were studied cross-sectionally and prospectively in order to discern which variables may account for the gender difference in such reports. A representative sample of Norwegian students (N= 9,679) in grades 7-12 were followed from 1992 to 1994. More girls (10.4%) than boys (6.0%) reported a previous attempt and more girls (3.3%) than boys (1.9%) reported an attempt during the study period. The gender difference in previous suicide attempts was significantly reduced when depressed mood was controlled, and was no longer significant when disordered eating was included. There was no gender difference in future attempts when previous attempts, depressed mood, physical appearance, pubertal timing, and romantic involvement were controlled. Girls' higher level of risk factors may account for their higher level of self-reported nonfatal suicidal behavior.     

The Turing Test as Interactive Proof

In 1950, Alan Turing proposed his eponymous test based on indistinguishability of verbal behavior as a replacement for the question “Can machines think?” Since then, two mutually contradictory but well‐founded attitudes towards the Turing Test have arisen in the philosophical literature. On the one hand is the attitude that has become philosophical conventional wisdom, viz., that the Turing Test is hopelessly flawed as a sufficient condition for intelligence, while on the other hand is the overwhelming sense that were a machine to pass a real live full‐fledged Turing Test, it would be a sign of nothing but our orneriness to deny it the attribution of intelligence. The arguments against the sufficiency of the Turing Test for determining intelligence rely on showing that some extra conditions are logically necessary for intelligence beyond the behavioral properties exhibited by an agent under a Turing Test. Therefore, it cannot follow logically from passing a Turing Test that the agent is intelligent. I argue that these extra conditions can be revealed by the Turing Test, so long as we allow a very slight weakening of the criterion from one of logical proof to one of statistical proof under weak realizability assumptions. The argument depends on the notion of interactive proof developed in theoretical computer science, along with some simple physical facts that constrain the information capacity of agents. Crucially, the weakening is so slight as to make no conceivable difference from a practical standpoint. Thus, the Gordian knot between the two opposing views of the sufficiency of the Turing Test can be cut.     

Is IQ in Childhood Associated with Suicidal Thoughts and Attempts? Findings from The Mater University Study of Pregnancy and Its Outcomes

This study explores associations of IQ at age 14 with adult symptoms of suicidal thoughts and attempts at age 21. Analysis was based on the Mater University Study of Pregnancy and its outcomes, an Australian prospective birth cohort study started in Brisbane Australia in 1981. We assessed associations with suicide thoughts, plans, and attempts. We used two measures of IQ: the Raven's Standard Progressive Matrices and the Wide Range Achievement Test. In multivariable analyses, there was an inverse association between Raven's IQ and suicide thoughts, plans, and attempts, but no strong evidence of an association between the WRAT3 and the three suicidal items. Specific aspects of intelligence may be associated with suicidal thoughts, plans, and attempts.     

Trends and monthly variations in the historical record of suicide in Japan from 1976 to 1994

Monthly suicide rates in Japan were analyzed for the period from 1976 to 1994 to clarify trends and recurring effects. The data were separated by sex, and the least-squares method was used. The major findings were (1) a significant positive correlation between unemployment rate and suicide rate for both sexes, (2) the suicide rate was highest in April for both sexes, and (3) an upsurge in male suicide mortality was noted from 1983 to 1990. These findings may well be associated with socioeconomic factors as well as neurobehavioral variables.     

The Relationship Between General Population Suicide Rates and Educational Attainment: A Cross‐National Study

Suicides are associated with both high and low levels of intelligence and educational attainment in both individual‐level and aggregate‐level studies. A cross‐national study examining the relationship between general population suicide rates (y) and educational attainment (x) was undertaken with the a priori hypothesis that the relationship would be curvilinear and follow a U‐shaped curve with the quadratic equation Y = A + BX + CX², where A, B, and C are constants. Data on suicide rates and the Education Index (a proxy measure of educational attainment) were ascertained from the World Health Organization and the United Nations Web sites, respectively. The main finding was the predicted curvilinear relationship between general population suicide rates, in both sexes, and the Education Index fit the above quadratic equation. Given the cross‐sectional study design, a causal relationship cannot be assumed. The impact of educational attainment on general population suicide rates may occur through interaction with other factors, mediation of the effects of other factors, or by its effects being mediated by other factors, and require further study.     

Brain perfusion and neuropsychological test scores: A correlation study in aphasics

In 26 patients suffering from the pure types of aphasias (11 total, 6 motoric, 5 sensory, and 5 amnesic), hemispheric and regional cerebral blood flow were measured and the flow values were correlated with psychological test scores including Wechsler Adult Intelligence Scale (WAIS), Token Test, Benton Test, and word fluency tests. With respect to the flow values, an overall difference between the groups of aphasics was proved by analysis of variance [regional cerebral blood flow (rCBF): F(3,22) = 13.77, p < .001]. The location of mainly impaired brain perfusion was not always confined to the centers within the speech area expected in view of the clinical disturbance, but most patients had neurologic deficits in addition to their aphasia. High correlations were found between the rCBF values within ischemic foci and WAIS subtests, as well as Token Test and word fluency tests. The correlation coefficients calculated between hemispheric flow and the psychological data indicated, in many instances, the same dependency, but did not attain the high statistical significance obtained with the regional values. The results show dependencies of several aspects of mental function upon cerebral perfusion and provide information for possible mechanisms responsible for the disturbance of nonverbal intelligence in aphasics.     

Suicidal behavior and cognitive flexibility: design and verbal fluency after attempted suicide

Aspects of problem solving were measured in nine male psychiatric patients, hospitalized after attempted suicide. Testing took place within 3 weeks (except for one patient) of the suicide attempt. Controls were patients with chronic idiopathic pain and healthy volunteers. Suicidal patients had significantly lower scores on general intellectual tests and in verbal and design fluency. No differences in problem solving (the Perceptual Maze Test and the Wisconsin Card-Sorting Test) and flexibility (the Uses of Objects Test and the Stroop Test) were found. The results are interpreted as indicating a decreased ability of suicidal patients to generate new ideas, when no alternatives are provided.