General Mental Ability

John Manning

Overview History of General Mental Ability

Definition, Models Measures of GMA Applications

GMA and Job Performance Individual Differences

Race, Gender, Age Alternatives?

What is GMA? It goes by many names: g, general mental

ability, IQ, intelligence A general measure of cognitive functioning

that should work across several different domains

First proposed by Francis Galton (1888), an English geneticist and relative of Darwin

Spearman (1904) proposed “g”- a general underlying intelligence factor that accounted for correlations between different areas on measures of intelligence.

It remains one of the most studied of all human characteristics

Spearman’s g Model and later models

Just how positively correlated are these subdimensions?

1 2 3 4 5 6 7 8 9 10Science 1.00Arithmetic 0.73 1.00Word knldg 0.82 0.72 1.00Paragraph 0.72 0.70 0.82 1.00Numeric 0.57 0.63 0.65 0.64 1.00Coding 0.51 0.55 0.60 0.61 0.72 1.00Auto+shop 0.68 0.59 0.61 0.51 0.38 0.33 1.00Math knldg 0.70 0.82 0.69 0.67 0.62 0.54 0.47 1.00Mech comp 0.71 0.70 0.64 0.57 0.45 0.41 0.75 0.62 1.00Electronic 0.77 0.68 0.72 0.63 0.47 0.42 0.76 0.60 0.75 1.00

Source: National Longitudinal Study of Youth ASVAB Scores, sample size is 11878 test takers

Factor Eigenvalue Difference Proportion Cumulative1 6.40 5.64 0.91 0.912 0.76 0.54 0.11 1.023 0.22 0.08 0.03 1.054 0.14 0.16 0.02 1.07

Correlation between the supposedly distinct ACT and SAT?R=0.91; R2=0.82

General mental ability and stability

The genetic inheritance of GMA Two statistics:

h2 (genetic effect) c2 (shared effect)

The effects of heredity only get stronger with age

Correlates of GMA Childhood outcomes

Average r=0.50 with school performance However, children in Japan and China know

more math than American children even though IQ scores are very similar

Average r=-0.19 with juvenile crime General psychomotor skills

Reaction speed r=.30 Judgment speed r=.55

GMA and Stability Is it really a trait? Is it stable?

Test re-test Age 6 to 18=0.77 Age 12 to age 18=0.89 Even higher correlations if tests are given on multiple

occasions What does this mean?

It means that rank order is very stable over time It does not mean that an average (100 IQ) 6 year old

can do what an average 18 year old can do

Correlation of GMA (1980) with life outcomes (1990)Sample size = 8891 (NLSY)

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Education Income Self-esteem Weeksunemployed

Criteria

Co

rrel

atio

n

Data clearly show that general mental ability as measured by the ASVAB is correlated with education levels, income, self-esteem, and weeks of unemployment even with a 10-year gap between measures

Measures of GMA General Aptitude Test Battery (GATB) Wonderlic Personnel Test Armed Services Vocational Aptitude Battery

(ASVAB) IQ Tests (WAIS-IV, Stanford Binet, etc.)

Examples of items from the Wonderlic Personnel Test

Examples of items from the GATB

Examples of items from the GATB

Overall it seems like GMA is a perfect selection tool It’s very stable over time It’s related to measures of learning ability

and adaptability It’s one of the best predictors of job

performance available The tests are cheap (about $2.00 per

applicant tested) It really doesn’t matter which test you use

since they all measure the same thing But…

…there are potential problems with GMA test scores The subtests show differences for gender

Women score higher on verbal intelligence Men score higher on visual-spatial intelligence

and the math section of the SAT These differences are not very great and there

are massive overlaps However, overall IQ scores are basically

equivalent for men and women

GMA Scores and Race/EthnicityThere are clear differences in GMA scores based on ethnicity African-Americans scored about 1

SD below Whites, although more recent data suggests this difference is closer to 0.6 to 0.7 SD

Latinos score between Whites and African-Americans

Asians score slightly higher than Whites

Ashkenazi Jews score about ½ SD higher than other White groups

Returning to our conception of biased from earlier

GMA tests predict just as well for both groups, but one group gets lower scores

This passes the equity standard, but not equality

There is no factual or logically rigorous reason to say this is okay or not

GMA for selection

Job complexity

Proficiency ratings

Training success

General job familiesHigh (synthesizing/coordination) 0.59 0.50 15%Medium (compiling/computing) 0.51 0.57 63%Low (comparing/copying) 0.40 0.54 18%

Industrial job familiesHigh (setup work) 0.56 0.65 3%Low (feedback/offbearing) 0.23 n/a 2%

GATB Validity for: % of U.S. Workers in these

occupations

GMAEverything

else

Nuclear weapons specialist 77.3% 0.8%Air crew operations specialist 69.7% 1.8%Weather specialist 68.7% 2.6%Intelligence specialist 66.7% 7.0%Fireman 59.7% 0.6%Dental assistant 55.2% 1.0%Security police 53.6% 1.4%Vehicle maintenance 49.3% 7.7%General maintenance 28.4% 2.7%

Percentage of training success explained by:

The Relation Between General Mental Ability (GMA) and Performance in Job Training and on the Job: Representative Findings From Meta-Analyses Performance measuresStudy Occupation On the job In

trainingHunter and Hunter (1984) Medium complexity .51 .57

Pearlman et al. (1980) Clerical .52 .71

Hirsh et al. (1986) Law enforcement .38 .76

McHenry et al. (1990) Military—enlisted .63b NR

McHenry et al. (1990) Military—enlisted .65c NR

Hunter (1986) Military—enlisted NR .63

Ree et al. (1994) Military—enlisted .45 NR

Ree and Earles (1991) Military—enlisted NR .60

Schmidt et al. (1979) First-line supervisors .64 NR

Schmidt et al. (1979) Administrative clerks .67 NR

Schmidt et al. (1980) Computer programmers .73 NR

Callender and Osburn (1981) Refinery workers .31 .50

Applicant reactions to GMA tests In general, results suggest applicants tend

to find GMA tests acceptable They especially like tests that are called

“personnel tests” They like tests more when they are paired

with individual interview information They usually like tests of knowledge and

abilities more than they like personality tests or biodata.

Bobko, Roth, & Potosky:Cognitive Ability and Alternative Predictors

Their meta-analytic matrix shows that structured interviews, conscientiousness, and biodata all have much lower d-scores than cognitive ability in terms of prediction, and many of these alternatives have good correlations with job performance

Validity vs. Value GMA is the single strongest predictor of

performance Value of interviews, collecting biometric data,

etc.?

To wrap it up… GMA is the totality of mental processes

involved in adapting to the environment. Underlying component of all different aspects

of intelligence. Stable over time, strong genetic/heredity

component Strong predictor of future job performance,

especially with complex and technical jobs. People like GMA tests. Value of alternatives?