This section describes the tests, inventories, and questionnaires administered to the reared apart twins. References listed at the end are those not provided in the text.

General mental abilities

Wechsler Adult Intelligence Scale (WAIS) Source: Wechsler (1955) The WAIS is an individually administered intelligence test consisting of six verbal and five performance (non-verbal) subtests. It yields an age- and sex-corrected intelligence quotient or IQ. Raven Progressive Matrices (RPM), Mill-Hill (MH) Composite Source: Raven (1986) The RPM is a widely used non-verbal test of problem-solving skill. The MH is a multiple choice word knowledge test. The two age- and sex-corrected scores are transformed to a mean of 50 and a SD = 10. Their sum yields a separate estimate of IQ. First Principal Component (PC) of the Hawaii Ability Battery (HAB) and Comprehensive Ability Battery (CAB) Source: HAB: DeFries et al. (1979); Source: CAB: Hakstian and Cattell (1978)

SPECIAL mental abilities

The HAB used in the MISTRA is an expanded version of the battery used in the Hawaii Family Study of Cognition. The MISTRA version also included the Identical Pictures, Cube Comparisons, and Paper Folding subtests from the Educational Testing Service of Kit Factor-Referenced Cognitive tests. The CAB consists of twenty separate subtests. Brief descriptions of each special mental ability the twins completed are presented below. HAB = Hawaii Ability Battery, CAB = Comprehensive Ability Battery, PMA = Primary Mental Ability; Factors: V = Verbal, S = Space, PSA = Perceptual Speed and Accuracy, M = Memory, ETS = Educational Testing Service, O = Other Tests

Hawaii Battery

Vocabulary. Subject identifies which of 4 alternatives is a synonym of the target word (PMA) V Visual Memory (Immediate). Subject memorizes pictures of 40 common objects and identifies which are contained in a new list of 40 objects. M Subtraction & Multiplication. Subject subtracts 2-digit numbers and multiplies a 2-digit number by a 1-digit number (ETS) O Lines & Dots. Subject forward traces a path through a grid to pass through as many bolded dots as possible. PSA Word Beginnings and Endings. Subject generates as many words as possible that begin and end with specified letters (ETS) O Card Rotation. Subject identifies all of 8 alternatives that are a 2-dimensional rotation of the probe stimulus (ETS) S Visual Memory (Delayed). Following 4 intervening tests (about 20 minutes), subject is tested again for recognition of originally memorized objects. M Pedigrees. Subject answers questions concerning familial relationships, given access to a schematic family tree (PMA) O Mental Rotations. Subject identifies which 2 of 4 alternatives are rotations of a 3-dimensional probe stimulus (Vandenberg) S Identical Pictures. Subject identifies which of 5 alternative figures is identical to the probe figure (ETS) PSA Paper Form Board. Subject shows how identical component figures can be used to constitute the desired arranged composites (ETS) S Hidden Patterns. Subject identifies which spatial patterns contain the probe figure (ETS) S Things Categories. Subject generates as many instances as possible of things meeting a specified criterion (ETS) O Cube Comparisons. Subject decides whether 2 cubes, with their 3 exposed sides labeled, are rotations of each other (ETS) S Paper Folding. Subject identifies which of 5 unfolded alternatives has a pattern of holes consistent with a single hole placed in the folded probe (ETS) S Different Uses. Subjects generate novel uses for common objects (ETS) V

Comprehensive Ability Battery

Vocabulary. Subject identifies which of 4 alternatives is a synonym of the probe word. (PMA) V Proverbs. Subject identifies which of 4 alternatives is a synonym of the probe saying. V Number. Subject completes arithmetic problems. O Space. Subject identifies all of 8 alternatives that are a 2-dimensional rotation of the probe stimulus. S Speed of Closure. Subject identifies an incomplete word and chooses it from a list of words with their letter order scrambled. O Perceptual Speed. Subject identifies which pairs of numbers or letters are the same. PSA Induction. Subject identifies one of five-letter series that does not follow the same rule as the others. O Flexibility of Closure. Subject identifies the pattern found in a series of figures. S Associative Memory. Subject associates a meaningless figure with a 2-digit number and identifies the number from a list when shown the figure. M Mechanical Ability. Subject identifies tools and mechanical principles. O Meaningful Memory. Subject associates an item with a descriptor and identifies the descriptor from alternatives when they are presented after an interfering task. M Memory Span. Subject completes a forward digit span task. M Spelling. Subject chooses the incorrectly spelled word from a list of five. O Word Fluency. Subject rearranges the letters of a word to form new words. O Other Special Mental Ability Tests Slossen Oral Reading Test (SORT). Source: Slossen (1984) The SORT includes six lists of 20 words each. The words are of increasing difficulty from preschool through high school reading levels. The test assesses level of oral word recognition, word calling, or reading level. Woodcock-Johnson Reading Mastery Test Source: Woodcock (1987 Form G) (WJRMT). The WJRMT includes a list of 105 words of increasing difficulty from preliminary to beyond high school reading levels. It assesses level of word identification. Spelling Test Source: Dr. Richard Venezky (computerized word list) Subjects listened to 37 words read to them on a tape with each word used in a sentence and wrote each word on an answer sheet. The list included words with high grapheme to phoneme correspondence (for which standard spelling rules apply) and words with low correspondence (for which visual learning is required). Reading Passages (3) Dr. Jay Samuels (from published sources) Subjects read three half-page passages aloud, then reported what they remembered reading. Topics included sex differences in temperature sensitivity, eye movements while reading, and the nature of job success. Psychological Battery – 1 • Multidimensional Personality Questionnaire (MPQ) Source: Tellegen (1982, 1985) The MPQ (formerly the Differential Personality Questionnaire, or DPQ) is a self-report instrument that yields 11 personality dimensions and three higher order factors. Abbreviated descriptions of the primary scales and higher order factors are listed below: Personality Dimensions: High Scorers versus Low Scorers 1. Well-Being: happy, cheerful disposition vs. experiences little joy or excitement 2. Social Potency: forceful and decisive vs. prefers others to take charge 3. Achievement: works hard vs. avoids demanding projects 4. Social Closeness: sociable and likes people vs. likes being alone 5. Stress Reaction: nervous and easily upset vs. fears and worries are set aside 6. Alienation: feels mistreated and betrayed vs. feels fairly treated 7. Aggression: vindictive and physically aggressive vs. non-violent and avoids aggression 8. Control: reflective and cautious vs. spontaneous and risk-taking 9. Harm Avoidance: prefers safety and lack of excitement vs. enjoys risk and adventure 10. Traditionalism: endorses high moral standards vs. rebellious and questions authority 11. Absorption: caught up in sensory and imaginative experiences vs. realistic Higher Order Factors 1. Positive Emotionality: Well-Being, Social Potency, Achievement, and Social Closeness 2. Negative Emotionality: Stress Reaction, Alienation, and Aggression 3. Constraint: Control, Harm Avoidance, and Traditionalism • Family Environment Scale (FES-R) Source: Moos and Moos (1986) This self-report instrument consists of 90 true-false items relating to subjects’ perceptions of their family environment. • Musical Interests Questionnaires Source: Coon and Gregory (1989) This form asks about playing an instrument, level of proficiency, reading music and general musical interests. • Minnesota Multiphasic Source: Hathaway and McKinley, 1940) Personality Inventory (MMPI) The MMPI includes over 500 behavioral style and preference items, rated as “true,” “false” or “can’t say.” It yields ten clinical scales. • Entertainment Questionnaire (EQ) MISTRA The EQ asks about the frequency of reading books and magazines, pursing hobbies, attending sports events, and attending artistic events. • Fear Survey Carey (1977) The Fear Survey includes 156 items rated on a Likert scale (0 = no fear to 12 = frozen with fear). Items are organized into seven content scales and two validity scales.  • California Psychological Inventory (CPI) Source: Gough (1968) The CPI assesses the social interaction and interpersonal behavior of normal subjects. • CAB-E Source: Hakstian & Cattell (1976) The CAB-E assesses subjects’ aesthetic judgment by having them indicate their preferred design from twenty-six sets of two or three designs. Psychological Battery – 2 • Block Environmental Questionnaire (BEQ) Source: Block (1971) The BEQ is a retrospective environmental questionnaire that includes 92 items describing parental characteristics and the rearing family context. It follows a Q-sort format. • Life Style Questionnaire Source: McGue (unpublished) The Life Style Questionnaire assesses the frequency and regularity of working, reading, writing, exercising, and relaxing. • Behavioral Report (Rule-Breaking) Source: Bouchard, Jr. (unpublished) The Behavioral Reports asks subjects to indicate the frequency with which they break (broke) various rules and conventions at different ages. • Handedness Questionnaire Source: Crovitz abd Oldfield (1977) The Crovitz-Oldfield Inventory is a self-report form that asks subjects to indicate their preference for use of the right or left hand (on a 9-point scale) with reference to 20 unimanual and bimanual activities. Subjects also indicate their preferred hand posture (inverted or non-inverted) while holding a pen, as shown in a series of pictures. Behavioral administration of the 20 items and observation of hand posture took place after completion of the self-report. • Writing Sample I University of Minnesota This task required copying a typed paragraph describing the Coffman Student Union at the University of Minnesota. • Food Frequency Questionnaire (FFQ) Source: Fabsitz et al. (1978) The FFQ, developed by the National Heart and Lung Institute, obtains quantitative information on the frequency with which various foods are consumed and preferred times for meals and snacks. • Smoking Questionnaire (SQ) Source: Colorado Adoption Project The SQ poses questions about past and present smoking habits of the respondent and respondent’s parents. • Attitudes & Opinions (A & O) Source: Lykken (unpublished) The A & O questionnaire has subjects endorse one out of four statements concerning controversial social, political, and religious issues. • Occupational Interests (OI) Source: Lykken (unpublished) The OI Inventory has subjects indicate if they would “like, dislike” or are “indifferent” to pursuing different types of occupations, irrespective of income and prestige.  • Morningness-Eveningness Source: Horne and Ostberg (1976) Questionnaire (MEQ) The MEQ presents 13 items assessing timing of preferred sleep habits, peak performance in mental and physical activities, feeling best, and maximum alertness. • Public Opinion Inventory I Source: Wilson and Patterson (1968); (POI-I)/Attitudes Altemeyer (1988); Eaves et al. (1997) The POI-I consists of the Right-Wing Authoritarianism (RWA) Scale (30-item version) and the Wilson-Patterson (WP) Attitude Survey (28-item version). The RWA Scale is a self-report instrument that uses a Likert response format (+4 = very strongly agree to -4 = very strongly disagree). Items capture concepts of radicalism and tough-mindedness. The WP Survey (conservatism scale) asks subjects to “agree”, “disagree”, or indicate “uncertainty” with reference to various issues, e.g., the death penalty, astrology, and segregation. • Myers-Briggs Type Indicator (MBTI) Source: Myers and McCaulley (1985) The MBTI is designed to measure four bi-polar dimensions of personal preference, derived from Jungian personality theory. • Allport -Vernon-Lindzey (AVL) Source: Allport, Vernon, and Lindzey (1960) The AVL has subjects rank order sets of statements that reflect values across a range of topics. Psychological Battery – 3 • Sensation-Seeking-Form V (SSS) Source: Zuckerman (1978, 1979) The SSS-V has subjects choose an alternative from forty sets of two choices each that best describes their likes or feelings. The items comprise four scales (Thrill and Adventure Seeking, Disinhibition, Boredom Susceptibility and Experience Seeking. • Sentence Completion Test (SCT): Source: Loevinger (1985); Loevinger and Le Form 11-68 (1989) The SCT assesses ego level development by having subjects complete thirty-sex stem items on the gender-appropriate version (Form 11-68). • Briggs Life History Form (BLHF) Source: Briggs (1969) The BLHF includes 125 multiple choice items pertaining to parental behavior, childhood health, education, personality, and social behavior. • Rokeach Value Survey (RVS) Source: Rokeach (1973) The RVS has subjects rank order two sets of 18 values each in their order of personal importance. • General Behavior Inventory (GBI) Source: DePue et al. (1981). The GBI is a self-report inventory that assesses intensity and duration of behaviors and symptoms. It is based on a binomial model of psychiatric disorder. • Writing Sample II Source: MISTRA This task asks subjects to copy and compose various sentences, and copy a 26-item list of names of geographical locations. • Work Attitude Questionnaire (WAQ) Source: Buchholz (1978) The WAQ presents 60 work-related items and has subjects indicate their extent of agreement on a five-point scale ranging from -2 (strongly disagree) to +2 (strongly agree) • Organizational Questionnaire (OQ) Source: See above The OQ poses 15 questions related to feelings about the company or organization with which the respondent is associated. • Special Experiences Scale Source: Hood (1975) This scale assesses self-reported mystical experience. Subjects indicate the extent to which 32 different events are true of their own experience. • Public Opinion Inventory-2 (POI-2) Source: Lykken (unpublished) The POI-2 has subjects indicate their extent of agreement with 30 social issues. • Religious Interest Inventory (RII); Source: Allport and Ross (1967); revised by Age Universal Religious Orientation Gorsuch and Venable (1983) Scale (AUROS) The RII has subjects indicate their agreement (1 to 9 scale) with 20 statements concerning the practice and value of religion. • Purpose in Life Test (PIL) Source: Crumbaugh and Maholick (1964) The PIL has subjects evaluate 20 purpose in life statements using a 1 to 7 scale. Psychological Battery – 4 • Swedish Inventory I Source: Swedish Adoption Twins Study of Aging Neuroticism and Extraversion items from the Eysenck Personality Questionnaire. Subjects answer “yes” or “no” to 24 questions concerning their attitudes, opinions, interests, and other characteristics. • Swedish Inventory II Source: Swedish Adoption Twins Study of Aging Karolinska Scales of Personality. Subjects indicate the extent (1 to 5 scale) to which various attitudes, interests, and feelings are characteristic of themselves. • Alcohol & Drugs Use Surveys Source: MISTRA Subjects answer questions concerning their use of alcohol and drugs. • Minnesota Leisure Time Interest Source: Lykken Survey (MLTI) Subjects indicate the frequency with which they engage in 120 leisure time activities. • California Psychological Inventory (CPI) Source: Gough (1968) Subjects indicate the extent to which different personality traits and styles are characteristic of themselves. This inventory was included in our Psychological Batteries 2 and 4. • Self-Ratings Source: Lykken Subjects compare themselves to others (lowest 5% to highest 5%) with reference to specified traits and abilities, e.g., abstract intelligence and common sense. • Talents Source: Lykken Subjects indicate their level of expertise across forty different activities and abilities. • Jackson Vocational Interest Survey (JVIS) Source: Jackson (1977) Subjects choose their preferred occupation from 289 sets of two alternatives. • Sixteen Personality Factor (16 PF) Source: Cattell (1949; original version) Subjects respond to multiple choice items concerning interests and feelings. • Minnesota Importance Questionnaire Source: Gay et al. (1971) (MIQ) The MIQ is a 190-item paired-comparison instrument designed to measure twenty vocationally relevant need dimensions, e.g. ability utilization and achievement. Twenty additional items require absolute judgments of the importance of each outcome. Psychological Battery – 5 • Neuroticism-Extraverison Openness Source: Costa and McCrae (1989) Inventory (NEO-PI) The NEO-PI is a personality inventory that assesses the big five personality traits: openness to experience, conscientiousness, extraversion, agreeableness and neuroticism. • Temperament and Character Inventory Source: Cloninger (1987) (TCI). The TCI, based on a psychobiological model of personality, assesses both normal and abnormal behavioral patterns. It yields four temperament scales and three character scales. • Campbell Organizational Survey (COS7) Source: Campbell (1990) The COS7 measures employee job satisfaction and organizational effectiveness. • Dissociative Experiences Survey (DES) Source: Bernstein-Carlson and Putnam (1986) The DES asssesses behaviors along a continuum, ranging from “normal dissociative states” (e.g., daydreaming) to pathological forms (e.g., as indexed in the Diagnostic Statistical Manual). • Campbell Interest & Skill Survey (CISS) Source: Campbell (1993, 1995) The CISS measures self-reported vocational interests and skills. The various interest scales reflect an individual's attraction to specific occupational areas. • Dimensional Assessment of Personality Source: Livesley and Jackson (2009) Pathology-Basic Questionnaire (DAPP-BQ) The DAPP-BQ assesses personality disorders from mild to extreme trait manifestations. It is a 290-item self-report measure consisting of 18 scales, e.g., Affective Lability, Anxiousness, and Callousness. Miscellaneous Psychological inventories • Strong-Campbell Interest Inventory (SCII) Source: Hansen and Campbell (1985) The SCII measures career and leisure interests, yielding four scales: General Occupational Themes. Basic Scales, Personal Style Scales and Occupational Scales. • Adjective Check List (ACL) Source: Gough and Heilbrun (1983). Subjects indicate which of 300 adjectives are descriptive of the self. • ACL by Non-Twin Participants Source: Same as Above Non-twin participants use the ACL to describe the twin they are accompanying. • Stroop Color Word Test (SCWT) Source: Stroop (1935); Golden (1978) The SCWT is a test of mental attention and flexibility. The later, standardized version asks subjects to read color words, printed in black, XXX’s printed in different colors and color words printed in different ink colors. • Barron-Welsh Art Scale (BWAS) Source: Barron (1963); Barron and Welsh (1987) The BWAS is a non-verbal measure of creativity, as reflected in images drawn by subjects. Scores reflect personal style, social attitudes, and libidinal drives. • Visual Aesthetic Sensitivity Test (VAST) Source: Eysenck (1983) The VAST presents 42 pairs of designs, with slightly altered forms comprising each set (an original and a less superior version). Subjects indicate which member of the pair they prefer. • Social Networks Source: Bouchard Subjects indicate the nature and identity of important people in their lives. LABORATORY TESTS – PSYCHOLOGICAL Psychophysiology Source: Lykken (1982) The psychophysiological battery included an electroencephalogram (EEG; spontaneous brain wave spectra), evoked potentials (EVP; time required for the nerves to respond to stimulation) and skin conductance measures (in a habituation paradigm). Psychomotor Battery Source: Fox et al. (1996); Tiffin (1948) Psychomotor tasks included a hole steadiness test (involuntary hand movement), the Purdue Pegboard Test (gross movement of finger, arms and hands; fine fingertip dexterity) and the Rotary Pursuit Test (ability to keep a stylus on a moving target; 25 test trials/day). Information-Processing (IP) Source: Posner et al. (1969); Sternberg (1969); Shepard and Metzler (1971) The IP battery included the Posner Letter Identification Task (subjects indicate if two simultaneously presented letters are the same or different, under two conditions); Shepard-Metzler Cube Rotations (subjects decide if pairs of projected 3-dimensional figures are the same or different) and Sternberg Memory Search (subjects memorize digits to assess speed of active memory). PERSONAL interviews Life History Interview (LH) Source: Bouchard Questions covered events surrounding birth, separation from the twin, contact following reunion, rearing family background, brothers and sisters, places of residence, educational experiences, marriages, children, work histories, work satisfaction, current family situation, physical facilities in the childhood home, and religious interests. Life Stress Interview (LSI) Source: Bouchard The life stress interview asks about the timing and frequency of various ordinary life events (e.g., changes in work responsibilities) and stressful experiences (e.g., death of a pet). Videotaped Interview Source: Bouchard Individual videotaped interviews covered life history items, including rearing circumstances, hobbies, and interests. Twins were also asked to walk, throw and catch a set of keys, and draw pictures of a person and a house. Joint interviews asked twins to review their similarities and differences, describe the experience of meeting their twin, and indicate what they liked and disliked about the assessment. Twin Relationship Survey (TRS) Source: Segal, Hershberger, and Arad (2003). The TRS is a comprehensive form with items pertaining to relationships with the reared apart co-twin, rearing parents and non-twin siblings. Sexual Life History Interview (SLH) Source: Bohlen The SLH included a Sexual Meaning Survey (personal sexual significance of various concepts, e.g., weak-strong; happy-sad), a Sexual Life History Timeline (timing of sexual events, e.g., age at first intercourse; first attraction to a member of the opposite sex), a Sexual Events Questionnaire (previous and current sexual attitudes and practices, e.g., use of contraception; frequency of sexual relations), and a semi-structured Sexual Life History Interview (discussion of premarital and marital sexual histories). Male and female forms were available for the latter two protocols. medical examINATIONs Diagnostic Interview Survey (DIS) Source: Robins et al. (1981) The DIS is a structured interview for use with nonclinical populations. It covers a number of Diagnostic Statistical Manual-III diagnoses. Medical Life History Source: Segal, Grove, and Bouchard (1991). Medical life histories included a complete review of each twins’ past and current symptoms, illnesses, injuries and surgeries, and a review of systems. Attention was paid to specific abnormalities and problem areas, and specialists were consulted when necessary. Twins’ previous medical records were collected, when possible. Allergy Testing Source: Kohler et al. (1985); Hanson et al. (1991) Allergy testing included an allergy questionnaire, IgE testing (IgE [antibody] testing screens for Type 1 hypersensitivity), and serological tests for 14 allergens (RAST or radioallergosorbent test). 24-Hour Heart Monitor* Source: Hansen et al. (1984) Twins wore a 24-hour Holter monitor (ambulatory electrocardiocorder; Model 445B). This device records heart rate changes throughout the given period. Twins also maintained a written diary of when activities and events occurred while wearing the device. Blood Pressure Monitor* Source: Halberg Twins’ blood pressure was monitored over the course of one night during sleep. Model BP203X from Colin Medical Instruments (Komaki, Japan) was used. Periodontal Exam Source: Michalowicz et al. (1991a, 1991b, 1999, 2000) Periodontology is concerned with the health and appearance of the gums. Measures included probing depth, clinical attachment loss, gingivitis, plaque, proportional radiographic alveolar bone height, temporomanibular joint signs and periodontal bacteria. Dental Exam Source: Borass et al. (1998); Conry et al. (1993) The dental examination included evaluation of dental morphology and alignment, as well as inspection for lesions, malocclusions, rotations, dental restorations, and type of restorations. A soft tissue exam revealed the possible presence of gum disease. Bitewing radiographs enabled detection of molar cavities, and dental (study models) allowed co-twin comparison of tooth size. Blood Sample Source: Kohler et al. (1985); Segal, Grove, and Bouchard (1991) Blood samples were drawn for zygosity testing, as well as for basic laboratory tests including hematological blood count and renal chemistry battery. Specific measures included Ig quantitation, isotype-specific antibody quantitation and specific antibody activity. A fasting blood sample was taken for assessment of blood sugar levels. Pulmonary Exam Source: Bouchard et al. (1981); Hankins et al. (1982) The pulmonary exam included a pulmonary exposure history, smoking history, and specialized pulmonary function studies (spirometry, flow volume, pletysmography, diffusing capacity, closing volume, and slope of phase 3). OTHER medical exams Physical Exam Source: Tuna A physical exam was performed by a cardiologist (Tuna) so was done in reference to the cardiovascular system. It included a review of organ systems, test of vital signs and body measurements. Electrocardiogram (ECG) Source: Hanson et al. (1989) ECGs measure the electrical impulses of the heart. Twelve-lead ECG readings were obtained for each twin using 3-channel Hewlett-Packard recorders. Source: Hanson et al. (1989) A Vectorcardiogram (VCG) is a tracing of the direction and magnitude of the heart's electrical activity during a cardiac cycle. Some twins’ VCGs were recorded using the Frank lead system, but these data were not analyzed. Cardiac Measurements: PR Interval (time between the onset of atrial activity and ventricular activity), QRS Duration (simultaneous activation of the left and right ventricles; normal intervals are less than .10 seconds, longer intervals can indicate blockage), QT Interval (electrical depolarization of the left and right ventricles), QTc interval (QT interval corrected for heart rate), Ventricular Rate (time between QRTS complexes), P Duration (spread of electrical activity over the atrium). This information was drawn from www.madsci.com/manu/ekg-part.htm www.mdcalc.com/corected-qt-interval-qtc and other medical sources. Stress EKG (Treadmill) Source: Tuna A stress EKG test monitors heart functioning during exercise. The test can show if the blood supply is reduced in the arteries that supply the heart. Echocardiogram Source: Tuna Echocardiograms use ultrasound to provide one and two-dimensional images of the heart. Opthalmological Exam Source: Knobloch et al. (1985) Opthalmological exams included a brief medical history, and tests of visual acuity, refraction, ocular pressure and eye dilation. Retinal photographs and a fundus eye examination (inspection of internal eye structures) were also completed. Chest X-Ray Source: Bouchard (1984) The chest x-ray was done for the purpose of detecting major abnormalities. miscelLaneous assessments and interviews Photographs Source: MSTRA Each twin was photographed on the first half day of assessment as specified in the Photo Checklist in Appendix I. Twins were also photographed taking tests alone and together (across a table) during the week. All photographs were unposed. Voice Samples Source: Jenkins** Individual differences in voice quality (fundamental frequency and fundamental frequency range) were assessed by obtaining voice samples from subjects. Twins read the first paragraph of Fairbanks’ Rainbow Passage. Clinical Interview Source: Sines (unpublished) Unstructured clinical interviews were offered to, and completed by, the first twenty-three twin pairs. These unstructured sessions lasted between one and two hours. This opportunity was made available to twins as a courtesy and was not intended for data collection. Vitalogs* Source: Hanson et al. (1984) Vitalogs measure the activity of individuals (circadium rhythms of temperature) over a specified time period (48 hours). Anthropometry* Source: Johnson et al. (2008) Anthropometric measures included height, weight, fingerprints, palm prints, eye color, ear shape, head width and head length; spouses completed only the first four measures. Several years into the study a more extensive anthropometric battery was introduced and included 77 measures in the categories of Weight, Stature and Length; Head, Diameter, Skinfold, and Circumference. Requested Facial Action Test (REFACT) Source: Kendler at al. (2008) The REFACT videotaped participants’ facial expressions as they watched emotion-inducing film clips. Clinical Nutrition Study (Tufts University) Source: Elder et al. (2009) General Health Assessment (vital sign measurement, physical examination, health history, and blood sample) Body Composition Measurement (anthropometry, EKG: bioelectrical impedance analysis, underwater weighing [residual lung volume measurement], dual energy x-ray absorptiometry, total body potassium test, body water content, BOD POD: air displacement plethysmography, CT scans, and muscle and fat biopsies) Nutrient Intake Assessment (food intake measurement, food preference questionnaires [Drewnowski taste test, dietary restraint questionnaire [Stunkard & Messick, 1985], and taste tests) Energy Expenditure Assessment (resting energy expenditure [kcals/day and by indirect calorimetry], thermic effect of food [energy used in the digestion process], strength test, activity monitors, stress test [maximal oxygen uptake: treadmill], and questionnaires) Substrate Oxidation (RQ [respiratory quotient used to calculate basal metabolic rate, by indirect calorimetry] and nitrogen excretion during calorimetry) Metabolic Parameters (Insulin Sensitivity Test [Bergman model: blood samples with dextrose and tolbutamide administration], FFA levels, and IGF1, T3, T4, and TSH) The University of Pennsylvania Smell Source: Doty et al. (1984) Identification Test (UPSIT) This scratch and sniff test was introduced into the study in the early 1990s. *Medical and other measures also completed by spouse or travel companion. ** Jim Jenkins, formerly at the University of Minnesota, is now at the University of South Florida.