I now have data on 12 people who have taken both my crossword puzzle and a well normed verbal intelligence test (SAT verbal, Wechsler verbal index, WAIS-IV Information, WAIS-IV Similarities). Nine of these people are self-reported scores from readers and three are from family members I personally witnessed taking both the crossword and a verbal test. The Pearson r correlation between the crossword scores and the verbal intelligence test scores is an astonishing 0.86 confirming once again that vocabulary is a powerful test of IQ.

When all the verbal test scores are converted to the Wechsler IQ scale (U.S. mean = 100; SD = 15) and plotted along the Y axis, and crossword scores (out of 17) are plotted on the X axis, we get a remarkably linear relationship.

Source: https://www.graphpad.com/quickcalcs/linear2/

The sample has a mean verbal IQ equivalent of 126 (SD 13.8) and a mean crossword score of 11 (SD 4.4). From here we can make some rough equivalencies:

0 = verbal IQ 92

1 = verbal IQ 95

2= verbal IQ 98

3 = verbal IQ 101

4 = verbal IQ 104

5 = verbal IQ 108

6 = verbal IQ 111

7 = verbal IQ 114

8 = verbal IQ 117

9 = verbal IQ 120

10 = verbal IQ 123

11 = verbal IQ 126

12 = verbal IQ 129

13 = verbal IQ 132

14 = verbal IQ 135

15 = verbal IQ 139

16 = verbal IQ 142

17= verbal IQ 145

Because all the words in the crossword were selected at random and thus have a true zero point (retrieving none of the words in the sample), we can say some interesting things about the distribution of receptive vocabulary. Someone with a verbal IQ of 111 (average U.S. university graduate) has roughly twice the receptive vocabulary of the average American.

Someone with a verbal IQ of 120 (average person with advanced degree) has roughly triple the receptive vocabulary of the average American. These large gaps help explain why society is so stratified along educational and occupational lines.

These norms probably work best for people just under 40. Those above 40 may deserve a bonus of perhaps 1 IQ point a decade since retrieval ability declines with older age.