Reference:
 Willerman, L., Schultz, R., Rutledge, J. N., and Bigler, E. (1991), "In Vivo Brain Size and Intelligence," Intelligence, 15, 223-228.
Authorization:
 Contact authors
Abstract:
 Are the size and weight of your brain indicators of your mental capacity? In this study by Willerman et al. (1991) the researchers use Magnetic Resonance Imaging (MRI) to determine the brain size of the subjects. The researchers take into account gender and body size to draw conclusions about the connection between brain size and intelligence.

Willerman et al. (1991) conducted their study at a large southwestern university. They selected a sample of 40 right-handed Anglo introductory psychology students who had indicated no history of alcoholism, unconsciousness, brain damage, epilepsy, or heart disease. These subjects were drawn from a larger pool of introductory psychology students with total Scholastic Aptitude Test Scores higher than 1350 or lower than 940 who had agreed to satisfy a course requirement by allowing the administration of four subtests (Vocabulary, Similarities, Block Design, and Picture Completion) of the Wechsler (1981) Adult Intelligence Scale-Revised. With prior approval of the University's research review board, students selected for MRI were required to obtain prorated full-scale IQs of greater than 130 or less than 103, and were equally divided by sex and IQ classification.

The MRI Scans were performed at the same facility for all 40 subjects. The scans consisted of 18 horizontal MR images. The computer counted all pixels with non-zero gray scale in each of the 18 images and the total count served as an index for brain size.
Information about gender and body size (height and weight) are also included. The researchers withheld the weights of two subjects and the height of one subject for reasons of confidentiality.

Number of cases:
40
Variable Names:
  1. Gender: Male or Female
  2. FSIQ: Full Scale IQ scores based on the four Wechsler (1981) subtests
  3. VIQ: Verbal IQ scores based on the four Wechsler (1981) subtests
  4. PIQ: Performance IQ scores based on the four Wechsler (1981) subtests
  5. Weight: body weight in pounds
  6. Height: height in inches
  7. MRI_Count: total pixel Count from the 18 MRI scans
The Data:
 
Gender	FSIQ	VIQ	PIQ	Weight	Height	MRI_Count
Female	133	132	124	118	64.5	816932
Male	140	150	124	¥	72.5	1001121
Male	139	123	150	143	73.3	1038437
Male	133	129	128	172	68.8	965353
Female	137	132	134	147	65.0	951545
Female	99	90	110	146	69.0	928799
Female	138	136	131	138	64.5	991305
Female	92	90	98	175	66.0	854258
Male	89	93	84	134	66.3	904858
Male	133	114	147	172	68.8	955466
Female	132	129	124	118	64.5	833868
Male	141	150	128	151	70.0	1079549
Male	135	129	124	155	69.0	924059
Female	140	120	147	155	70.5	856472
Female	96	100	90	146	66.0	878897
Female	83	71	96	135	68.0	865363
Female	132	132	120	127	68.5	852244
Male	100	96	102	178	73.5	945088
Female	101	112	84	136	66.3	808020
Male	80	77	86	180	70.0	889083
Male	83	83	86	¥	¥	892420
Male	97	107	84	186	76.5	905940
Female	135	129	134	122	62.0	790619
Male	139	145	128	132	68.0	955003
Female	91	86	102	114	63.0	831772
Male	141	145	131	171	72.0	935494
Female	85	90	84	140	68.0	798612
Male	103	96	110	187	77.0	1062462
Female	77	83	72	106	63.0	793549
Female	130	126	124	159	66.5	866662
Female	133	126	132	127	62.5	857782
Male	144	145	137	191	67.0	949589
Male	103	96	110	192	75.5	997925
Male	90	96	86	181	69.0	879987
Female	83	90	81	143	66.5	834344
Female	133	129	128	153	66.5	948066
Male	140	150	124	144	70.5	949395
Female	88	86	94	139	64.5	893983
Male	81	90	74	148	74.0	930016
Male	89	91	89	179	75.5	935863