Children know the difference between right and wrong before they reach the age of two, according to new research _________ recently.

Scientists have _________ that babies aged between 19 and 21 months understand fairness and can _________ it in different situations. They say it is the first time that having a _________ of fairness has been identified in children at such a young _________.

Researchers say babies will watch a _________ for longer if they think it contains something unfair, so in two experiments the babies were _________ on how long they watched a live scenario (情景) about fairness.

In the first, 19-month-olds _________ two giraffe puppets (玩偶) given either a toy each or both toys to one of the giraffes. Longer looking times _________ that something was unusual or __________ to the baby. In this experiment, three-quarters of the babies looked longer when one giraffe got __________ toys.

In a second experiment, two women __________ each other with a pile of small __________ between them and an empty plastic box in front of each of them. In one scenario, one woman __________ put the toys away, while the other kept playing, but both women were given __________. In another scenario, both women put the toys away and both got a reward. The __________ 21-month-old babies looked reliably __________ when the worker and the slacker (偷懒的人) were rewarded equally.

Psychologist Stephanie Sloane, who led the study at Illinois University, said: “We discovered that 19 and 21-month-old babies have a general __________ of fairness, and they can apply it __________ to different situations.”

The __________ appear in Psychological Science, a journal published by the Association for Psychological Science.

Two new studies add further pieces to the jigsaw puzzle that is human evolution. One reports a (n)_________extra member of the genus Homo. The other casts _________ on possible interbreeding between three human species in the Middle East.

Homo longi--- “Dragon man” into English from Chinese, via Latin---is not a (n)_________find, but a reinterpretation of an existing one. The cranium (头盖) in question was dug up in Harbin in1933 and is_________at Hebei GEO University, in Shijiazhuang. It is146,000 years old and was_________ badged as an archaic form of Homo sapiens (智人). But Ni Xijun and Ji Qiang, who work at the university, disagree. As they report in the Innovation, the cranium would indeed have contained a brain similar in size to a modern human’s, but the fossil is too large to be sapiens and has molars and eye sockets which dwarf those of people today. Dr Ni and Dr Ji also realised that it is too long and low to be sapiens. It lacks the_________of a modern human cranium.

This is good news for_________ of the recent- African- origin theory, which holds that most non-African human beings alive today are descendants of a small number of migrants who_________to Asia from the Horn of Africa about60, 000 years ago, meaning that any non- African human fossil from before that date is probably of another species descended from earlier, non- sapiens departures from Africa. The question was, which earlier species did the Harbin fossil represent? By_________it with known archaic humans, including Homo erectus, Homo floresiensis, Homo heidelbergensis and Homo neanderthalensis, Dr Ni and Dr Ji__________ that it was none of them, and must therefore be new to science and so worthy of its own name. There is, however, one other possibility-for there is a now-extinct type of human of which no cranium has yet been __________ . Homo denisova’s existence was established by the extraction of DNA from a finger bone, and traces of that DNA, a remnant of interspecies breeding，still exist in modern humans, notably in China. Since one of the Harbin fossil’s molars perfectly matches the size and root __________ of a molar from the Denisova cave in Russia, after which Homo denisova is named, it may be that Dr Ni and Dr Ji have actually identified the first Denisovan cranium.

The other study, published in Science by Israel Hershkovitz of Tel Aviv University, also speaks to the question of interspecific interbreeding. Even supporters of the recent-African-origin theory recognise that there was, __________, an earlier “ leakage” of Homo sapiens from north-east Africa into the Levant. Dr Hershkovitz and his colleagues have been examining fossils of __________ antiquity—120,000-l40,000 years-- collected from Nesher Ramla, a site in Israel. These, they found, have sapiens-like jaw bones, Neanderthal-like molars and crania similar to those of Homo erectus. This suggests to them that they are the __________ of miscegenation between all three.

Child developmental psychologist Jean Piaget convinced us that young, undeveloped minds couldn’t handle complex concepts because they simply weren’t experienced or mature enough yet. Piaget, _________, believed that young kids could not understand cause and effect, that they couldn’t think logically, and that they also couldn’t handle abstract ideas.

But child development specialists are finding out that preschoolers without any formal education may have the capacity to understand more complex concepts than we give them _________ for.

Alison Gopnik, professor of psychology at University of California Berkeley and her team devised a way to test how well young kids understand the abstract concept of _________ cause and effect—the idea that there may be more than one cause for a single effect. They picked preschoolers around 4 years old _________ undergraduates. The study _________ a toy that could be turned on by placing a single blue colored block on the toy’s tray, but could also be activated if two blocks-orange and purple-were placed on the tray.

The preschoolers were expert at _________ that the blue blocks turned on the toy, as did the purple and orange ones, but that the purple and orange ones needed to be paired together. The undergraduates, however, had a _________ time accepting the latter solution. Their previous experience in the world hampered their ability to accept the unusual rules that _________ the toy.

Researchers from Johns Hopkins University found a similar effect among preschoolers when it came to math. Previous studies showed that if you present infants with eight objects over and over until they got bored, and then showed them 16, they suddenly _________ interest and sensed that things change. Even before they are taught about numbers or amounts, then, infants seem to have a grasp on quantity. “All the evidence so far leads us to believe that this is something that babies come into the world with,” says Melissa Kibbe, co-author of that study. According to her research, the preschoolers had some __________ of quantity, and the appropriate amount that they needed to get from a small quantity to a larger one.

Kibbe’s and Gopnik’s recent work may have broader __________ for education, since current math curricula in schools may not be ideal for __________ the number sense that kids are born with. “There’s an exciting movement in psychology over the past decade, as we learn that students bring certain capabilities, or inborn knowledge that we hadn’t thought they had before,” says Jon Star, at the Harvard University Graduate School of Education.

Though it may be too early to __________ such findings to the classroom, the results lay the ground work for studying similar inborn skills and how they might be better understood. “The hard part is, __________, how you build up and upon this intuitive knowledge in a way that allows a child to capture the complexity but not hold them back.” says Tina Grotzer, associate professor of education at Harvard. Taking advantage of a child’s still developing sense of numbers and quantities is one thing, but __________ it with too many new constructs about algebra, unknowns, and problem solving may just end up negatively affecting his learning and academic performance. “As soon as concepts get big and complex, there are all sorts of perceptual, attentional, and cognitive costs and challenges involved,” she says.