List of common misconceptions about language learning

Language learning is subject to several misconceptions. It is common for people to rely on their own intuitions about language learning, though they would not do so with other technical subjects such as physics (a phenomenon known as "folk linguistics"). However, these intuitions are often contradicted by scientific research.
Childhood language acquisition.
Children learn their first language effortlessly.
Learning a first language is not rapid for children. Children spend years learning their mother tongue, and the process continues well into their school years. At seven years old, for example, many children have difficulties creating passive-voice sentences.
Second-language acquisition.
Related languages are easier to learn.
Early linguists theorized that similar or seemingly related languages facilitate acquisition of second language (L2). However, the learners' first language will always have both positive and negative transfer effects on their L2, regardless of how many features are the shared. At the same time, evidence for the relation between languages or language families have been evolving throughout history. Many features that were once considered the same across languages were discovered to have completely different origins, etymology, or, in many cases, folk etymology.
Younger learners learn languages more easily than older learners.
It is often assumed that young children learn languages more easily than adolescents and adults. However, the reverse is true; older learners are faster. The only exception to this rule is in pronunciation. Young children invariably learn to speak their second language with native-like pronunciation, whereas learners who start learning a language at an older age only rarely reach a native-like level.
Intelligent people are better at learning languages.
General intelligence is actually quite a poor indicator of language-learning ability. Motivation, tolerance for ambiguity, and self-esteem are all better indicators of language-learning success.
Immersion is the best way to learn a language.
The ability for learners to develop their language skills depends to a large extent on the type of language input that they receive. For input to be effective for second-language acquisition, it must be comprehensible. Merely being immersed in a second-language environment is no guarantee of receiving comprehensible input. For example, learners living in a country where their second language is spoken may be lucky enough to interact with native speakers who can alter their speech to make it comprehensible; but equally, many learners will not have that same luck, and may not understand the vast majority of the input that they receive.
In addition, adult learners living in a foreign country may not have very high linguistic demands placed on them, for example if they are a low-level employee at a company. Without the incentive to develop high-level skills in their second language, learners may undergo "language fossilisation", or a plateau in their language level.
Classroom instruction can be useful in both providing appropriate input for second-language learners, and for helping them overcome problems of fossilisation.
Grammar study is detrimental to second-language acquisition.
The study of grammar is helpful for second-language learners, and a lack of grammar knowledge can slow down the language-learning process. On the other hand, relying on grammar instruction as the primary means of learning the language is also detrimental. A balance between these two extremes is necessary for optimal language learning.
Bilingual education.
Learning a second language hinders the development of the first language.
Learners can learn two or more languages without their first language development being adversely affected. There is no such thing as a "fixed amount of space" for languages in the brain. In reality, learners' first languages and their additional languages become part of an integrated system.
Once a child can speak a language, the language-learning process is complete.
Learning to speak a language conversationally is only part of the way towards becoming fluent in it. Just because a child can speak a language does not mean that they are yet capable of writing and understanding academic language. This kind of language is particularly important in school in the later grades. One study of 1,200 Canadian schoolchildren indicated that it may take between five and seven years longer to master academic language than to master conversational language.