At least harder than I’d thought. In language acquisition (which is based on English language acquisition) we learn that prepositions are acquired pretty early. There are charts that show that young children learn “in” and “on” early (about 2 years old) and they go on to learn others like, “under” and “off” as well as “up” and “down” pretty systematically as they develop.
In Spanish, development of prepositions hasn’t been studied in such detail. We know that “en” (in or on) is learned around age 3. Other early forms are “a” (to) and “entre” (between). Later, kids learn to use “por” (because of/for) and “desde” (since).
One things we do know is that there are prepositions that work the same between two languages and others that work differently. In addition, conceptual space may be carved up differently. An important difference between Spanish and English is that Spanish is a verb-framed language. So, information about the path of movement and directionality is expressed in the verb. English is a satellite framed language. So, some of these meanings are expressed in a preposition or prepositional phrase.
In a recent study, we examined how accurately children between the ages of 7 and 9;11 repeated prepositions in sentences. We found that bilingual Spanish-English speakers were more accurate in Spanish (81%) compared to English (69%). But note, they are not that close to 100% even in Spanish.
In English, children were most accurate on “outside” (89%) followed by “for” (76%). They were least accurate on “at” (42%) and “on” (48%). In Spanish, they were most accurate on “cuando” (when), sin (without), and con (with), at 97%, 91%, and 89% levels of accuracy. They were least accurate on “en” (in/on) and “de” (of/from) and produced these with 56% and 58% levels of accuracy.
We were also interested in what predicted their accuracy levels and if knowledge of preposition use in one language was related to the other language. Use of English was most strongly associated with English preposition accuracy. Other factors (including Spanish preposition accuracy, mother education and age of first English exposure) also were predictive, but these were not as strongly associated as was current use of English.
One thing that is important to know is that the children remembered most (close to 90%) of the sentences they repeated. But, they had particular difficulty with prepositions. It may be that the differences in how prepositions are expressed in the two languages is especially challenging for bilinguals at this stage in development. Educationally, we might note that some errors may persist longer in English (e.g., at and on). While others “outside” and “for” may not be as challenging.