Practice Reading: Study on Twins: Dual Nature

The scientific exploration of twins dates back to the late 19th century, when Francis Galton, an early geneticist, observed that twins could be classified into two types: identical twins originating from a single egg, and non-identical twins resulting from two eggs. This insight proved pivotal, leading to the formulation of what is now known as the twin rule of pathology in 1924, marking the beginning of twin studies.

B

The twin rule of pathology posits that any heritable disease shows greater concordance (i.e., joint presence or absence) in identical twins compared to non-identical twins, and even greater concordance in non-identical twins compared to non-siblings. For instance, early studies found a correlation of 0.4 in skin mole counts between identical twins, while non-identical twins showed a correlation of only 0.2. A correlation score of 1.0 indicates perfect correlation, whereas a score of 0 indicates no correlation. This suggests that moles are heritable, but also indicates an environmental influence on mole development, as otherwise the correlation in identical twins would be close to 1.0.

C

Twin research indicates that the decision to start smoking is largely influenced by environmental factors, whereas the amount smoked once initiated is predominantly influenced by genetics. Similarly, while a person's religious affiliation is culturally influenced, there is a substantial genetic component to religious fundamentalism. Twin studies are also shedding light on the heritability of various aspects of human personality, ranging from neuroticism and anxiety to thrill-seeking and novelty-seeking, all of which exhibit significant genetic components. Parenting plays a role, but does not determine personality traits as previously thought.

D

Moreover, twin studies contribute significantly to our understanding of diseases such as cancer, asthma, osteoporosis, arthritis, and immune disorders. Ethically conducted, twins can also be involved in medical experiments. For instance, a study administering vitamin C to one twin and a placebo to the other showed no effect on the common cold. The overarching lesson from contemporary twin studies is that most human traits are influenced, at least in part, by genetic factors. However, the traditional dichotomy between nature and nurture often proves inadequate. Many genetic processes are influenced by environmental stimuli, with genes frequently activated or deactivated in response to external signals. Moreover, genes themselves can shape their environments, influencing human preferences for activities like sports or novelty-seeking, and possibly even guiding social interactions and experiences.

E

Historically, such research has been contentious. Josef Mengele, a Nazi doctor at Auschwitz during World War II, had a macabre fascination with twins, subjecting them to brutal experiments. Similarly, Cyril Burt, a British psychologist who studied the heredity of intelligence, tainted twin research with results that, in hindsight, appear suspiciously favorable. Some data on identical twins reared apart were likely fabricated. Following the war, prevailing social sciences, influenced by Marxism, were skeptical of genetic explanations for differences in human potential. Twin studies were thus viewed with suspicion.

F

However, the ideological landscape has shifted. The Human Genome Project and subsequent research have translated abstract genetic concepts into tangible DNA sequences. Nearly universally acknowledged now is the role of genes in sensitive areas like intelligence, with attention shifting to understanding how nature and nurture interact to shape biological outcomes rather than debating their relative importance. Twin studies, offering a unique framework for exploring these questions, have regained popularity, with many twins enthusiastically participating in research.

G

Research at the Twinsburg Festival began modestly with a single booth in 1979 but has since grown. Today, multiple groups of researchers gather under specially pitched tents to investigate various aspects of human perception, particularly the senses of smell, taste, and somatosensation (warmth, cold, pain, tingling, itching, etc.). For example, Paul Breslin from the Monell Institute oversees experiments where twins taste clear liquids and record their perceptions. This marks the third year of the Monell team's participation at Twinsburg. Dr. Breslin and colleagues aim to uncover how genes influence human perception, which is likely shaped by both genetic predisposition and life experiences. Even before birth, exposure to flavors like chocolate or garlic affects taste preferences later in life, though the impact of such prenatal experiences on taste perception remains unclear.

H

Nevertheless, genetic factors are clearly at play, such as in the ability to taste quinine. Some individuals find quinine intensely bitter even at low concentrations, while others, with different genetic backgrounds, are less affected. Twin studies illustrate this vividly: among identical twins, both will typically find quinine either strongly unpleasant or tolerable, whereas non-identical twins will show less agreement on its taste.

I

Across the tent, Dennis Drayna from the National Institute on Deafness and Other Communication Disorders in Maryland investigates hearing. He seeks to understand whether sound processing predominantly occurs in the ear or the brain after reaching the ear. Dr. Drayna previously participated in a twin study demonstrating the strong heritability of musical pitch perception. At Twinsburg, he tests different words or parts of words in the left and right ears of his twin volunteers. How individuals perceive the composite sound depends on their unique information processing methods, influenced significantly by genetics, according to Dr. Drayna.

J

In another part of the tent, Peter Miraldi from Kent State University in Ohio explores whether genes influence an individual's motivation to engage in communication. Given that twin studies have indicated heritability in personality and sociability, Miraldi considers this area promising. Nearby, a team of dermatologists from Case Western Reserve University in Cleveland examines the development of skin diseases and male-pattern baldness. Their objective is to identify the genes responsible for male hair loss.

K

The busiest part of the tent, however, was the queue for forensic-science research into fingerprints. The origins of this study are shrouded in mystery. For many months, the festival’s organisers have been convinced that the Secret Service – the American government agency responsible for, among other things, the safety of the president – is behind it. When The Economist contacted the Secret Service for more information, we were referred to Steve Nash, who is chairman of the International Association for Identification (IAI) and is also a detective in the scientific investigations section of the Marin Country Sheriff’s Office in California. The IAI, based in Minnesota, is an organisation of forensic scientists from around the world. Among other things, it publishes the Journal of Forensic Identification.

Questions 1-5

The Reading Passage has seven paragraphs A-K

Which paragraph contains the following information?

Write the correct letter A-K, in boxes 1-5 on your answer sheet.

NB  You may use any letter more than once.

1 Mentioned research conducted in Ohio

2 Medical contribution to the researches for twins.

3 Research situation under life-threatening conditions

4 Data of similarities of identical twins

5 Reasons that make one study unconvincing

Questions 6-7

Complete the following summary of the passages in Reading Passage 

Using NO MORE THAN TWO WORDS from the Reading Passage for each answer.

Write your answers in boxes 6-7 on your answer sheet.

The first one that conducted research on twins is called 6… . He separated twins into two categories: non-identical and identical twins. The twin research was used in a medical application in as early as the year of 7…

Questions 8-10

Choose the correct options from the following

Write your answers in boxes 8-10 on your answer sheet.

Please choose THREE research fields that had been carried out in Ohio, Maryland and Twinburgh?

• A. Sense
• B. Cancer
• C. Be allergic to Vitamin D
• D. Mole heredity
• E. Sound
• F. Baldness of men

Questions 11-13

Choose the correct options from the following

Write your answers in boxes 11-13 on your answer sheet.

Please choose THREE results that had been verified in this passage.

• A. Non-identical twins come from different eggs.
• B. Genetic relation between identical twins is closer than non-identical ones.
• C. Vitamin C has an evident effect on a cold.
• D. Genetic influence on smoking is superior to the environment’s
• E. If a pregnant woman eats too much sweet would lead to skin disease.
• F. Hair loss has been found to be connected with a skin problem.

Answers:

1. J (Đoạn J, “Elsewhere in the marquee, Peter Miraldi, of Kent State University in Ohio, was trying to find out whether genes affect an individual’s motivation to communicate with others.”)

2. D (Đoạn D, “More importantly, perhaps, twin studies are helping the understanding of diseases such as cancer, asthma, osteoporosis, arthritis and immune disorders.”)

3. E (Đoạn E, “Josef Mengele, a Nazi doctor working at the Auschwitz extermination camp during the second world war, was fascinated by twins.”)

4. B (Đoạn B, “This result suggests that moles are heritable, but it also implies that there is an environmental component to the development of moles, otherwise, the correlation in identical twins would be close to 1.0.”)

5. E (Đoạn E, “Some of his data on identical twins who had been reared apart were probably faked.”)

6. Francis Galton (Đoạn A, “THE scientific study of twins goes back to the late 19th century, when Francis Galton, an early geneticist, realised that they came in two varieties: identical twins born from one egg and non-identical twins that had come from two.”)

7. 1924 (Đoạn A, “That insight turned out to be key, although it was not until 1924 that it was used to formulate what is known as the twin rule of pathology, and twin studies really got going.”)

8. A (Đoạn G, “It was the team’s third year at Twinsburg. Dr Breslin and his colleagues want to find out how genes influence human perception, particularly the senses of smell and taste and those (warmth, cold, pain, tingle, itch and so on) that result from stimulation of the skin.”)

9. E (Đoạn I, “On the other side of the tent Dennis Drayna, from the National Institute on Deafness and Other Communication Disorders, in Maryland, was studying hearing. He wants to know what happens to sounds after they reach the ear.”)

10. F (Đoạn J, “They are looking at the development of skin disease and male-pattern baldness.”)

11. A (Đoạn A, “…realised that they came in two varieties: identical twins born from one egg and non-identical twins that had come from two.”)

12. B (Đoạn B, “The twin rule of pathology states that any heritable disease will be more concordant (that is, more likely to be jointly present or absent) in identical twins than in non-identical twins – and, in turn, will be more concordant in non-identical twins than in non-siblings.”)