'Mirror image' is a type of identical twinning. It can happen in any type of identical twins. When the split occurs late - more than a week after conception - the twins can develop reverse asymmetric features.
Mirror twins always come from a single fertilized egg and share the same genetic makeup. That said, the exact cause of the mirroring in some twin pairs is unclear. Some researchers suggest mirror twins occur when an egg splits later in the fertilization process. Eggs usually split within a week of conception (or less).
Mirror syndrome or triple edema or Ballantyne syndrome is a rare disorder affecting pregnant individuals. It describes the unusual association of fetal and placental hydrops with maternal preeclampsia.
Twins can sometimes talk in tongues
When twins mimic each other's babbles instead of their parents' speech, it's called idioglossia or cryptophasia. Twins often look to each other as language models and assign meaning to those jabbers. So, “pfft!” could mean “let's go!” to your tiny twosome.
Mirror-image twins is an unofficial phenomenon that occurs among identical twins almost 25 percent of the time, according to Dr. Nancy Segal, a psychologist and director of the Twin Studies Center at California State University, Fullerton.
It's a misconception that twins have identical fingerprints. While identical twins share many physical characteristics, each person still has their own unique fingerprint.
Monoamniotic-monochorionic Twins
These types of twins share a chorion, placenta, and an amniotic sac. This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords.
The short answer is that while there are plenty of stories out there about twins who claim to have read each other's minds and predicted when the other was in danger, Nancy Segal, PhD, director of the Twin Studies Center, at California State University, Fullerton, says that scientific research doesn't support the idea.
They were reflecting each other, like a mirror image. Mirror twins are identical twins whose fertilised egg split later in the zygotic stage – between 9-12 weeks, which is just shy of the formation of conjoined twins.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
The DNA of monozygotic twins tends not to be 100% identical, and epigenetic and environmental differences further widen the gap between twin pairs. It's not nature or nurture; it's a complex interaction between our genes, our environment, and our epigenetic markers that shape who we are and what illnesses befall us.
It is likely that twins' awareness of one another starts sooner than seven or eight months of age. An article by the late doctor, T. Berry Brazelton, observed that at age three to four months, an infant identical female twin seemed disoriented when her sister was removed from the room.
Twins share the same genes but their environments become more different as they age. This unique aspect of twins makes them an excellent model for understanding how genes and the environment contribute to certain traits, especially complex behaviors and diseases.
Young twins are together nearly all the time, and like any two people who spend most of their time together, they learn to rely on nonverbal or shorthand forms of communication. They're able to act intuitively, understanding each other's gestures, grunts, or vocalizations.
Twin-twin transfusion syndrome (TTTS) is a rare, serious condition that can occur in pregnancies. This happens when identical twins share a placenta (monochorionic). Abnormal blood vessel connections form in the placenta. They allow blood to flow unevenly between the fetuses.
The 244 individual twins' IQ's are normally distributed, with the mean = 96.82, SD = 14.16. The mean absolute difference between twins is 6.60 (SD = 5.20), the largest difference being 24 IQ points. The frequency of large twin differences is no more than would be expected from the normal probability curve.
Twins are competitive with each other and/or jealous of one another because of their unique and deep attachment, which creates judgments. This rivalry is based on the reality that twins measure themselves against each other from an early age.
What happens when one twin absorbs another? The vanishing twin's tissue gets absorbed by the surviving embryo(s) and the parent, too. This absorption process is completely harmless.
After all, while huge differences can and do happen with fraternal twins, identical twins are usually exactly that -- identical in skin, hair and eye color. But, actually, twins who start out with identical DNA always have slightly different DNA by the time they're born.
At age 7, the mean IQ score of twins was 5.3 points lower than that of singletons in the same family, and at age 9, the score was 6.0 points lower. The lower intelligence of twins in childhood may partly be a consequence of the reduced fetal growth and shorter gestations of twins, say the authors.
Fraternal twins
They are also known as 'dizygotic twins', or 'non-identical twins'. With fraternal twins, the two foetuses (developing babies) each have a separate placenta, inner membrane (the amnion) and outer membrane (the chorion). They don't usually look identical and might or might not be the same sex.
Many twins, whether due to nature or nurture, may simply have the same instincts, tendencies, or preferences, explaining why they may do eerily similar things simultaneously. Ultimately, regardless of whether it's described as telepathy, twins often share a special sibling bond that makes them especially close.
When a twin dies, the twinless twin longs to reconnect. The twinless twin may have phantom pain or feel half dead. He or she may feel a need to represent both him or herself and the deceased twin or may even take on behaviors of the deceased twin.
Having been raised in such close proximity—emotionally and physically—to their same-age sibling, many twins have this enormous capacity for empathy. However, this very enviable skill can become an emotional hindrance and complication when twins are grappling with separation issues.