Is it possible to say that the inhabitants of the colony are smarter, since they need to know two languages ​​(native and the language of the colonialists), in contrast to the inhabitants of the metropolis?

If the criterion for assessing the mind is considered only language skills, then, of course, it cannot be said so, since this criterion cannot indicate the level of mental development and intelligence. And the very concepts of mind and intellect are very blurred today. If, for example, the IQ level is taken as a basis, then residents of less civilized countries are usually smarter than residents of developed countries. For example, the IQ level of most illiterate Indians is much higher than that of European scientists.

In addition, the knowledge of languages ​​among the inhabitants of colonies and underdeveloped countries is at a very low level of spoken language. As a rule, they know only a few dozen words related to their activities and that's all, they are not able to conduct philosophical conversations or read scientific treatises in these languages.

This is an interesting question. All homo sapiens have an ability for languages, and language is still a fairly objective and utilitarian thing, from birth. I draw your attention to the fact that almost everyone, including people with a clinical diagnosis of idiocy, can master the language. Mastering a second language, at the level of "communication", is not a difficult thing. Actually, all migrant workers are mostly fluent in two or even more languages. But are they able to read a scientific article in a non-native (and even in their native?) Language? Poems? Rate theater, real humor? Read a philosophical treatise?

That is, the ability for languages ​​is basic for any person, and besides, bilinguals live longer and more productively. But the very fact of knowing several languages, even at a very good level, does not make a person neither smart, nor cultured, nor educated.

Measuring the mind by the number of languages ​​learned is not entirely correct. Statistically smart and stupid people should be about the same everywhere. However, in people who know two or more languages, the mind is much more flexible and adapted to quickly solving problems than monolinguals with approximately the same level of intelligence and education (this is due, in particular, to the fact that each concept or phenomenon is assigned not one, but two words, in two different languages; this speeds up access to information: roughly speaking, it goes through two channels faster than one).

Another point is that language is not the only means of development flexibility of mind. For example, if in the metropolis everyone is studying mathematics and logic, as well as literature, grammar, and other subjects, and in the colony they do not really teach anything about this, they only force them to learn a second language, it is very likely that the average citizen of the colony will be worse off solving various intellectual problems , even with all the benefits of knowing a second language to his brain. With harmonious development, bilingual surpasses monolingual with the same data, for example, in solving mathematical and logical problems; even if the apparent speed of solving such problems is the same, a bilingual will spend less energy on solving them than a monolingual - that is, his brain works more efficiently.