A third criterion for effective research on skills transfer is study over time. To be certain that students are transferring skills from their first language rather than using skills learned in their second language, researchers must study subjects who have received reading instruction in their first language prior to receiving it in their second language, and who have received sufficient first-language instruction to have developed a base of first-language skills that can be transferred. If the time frame involved in shifting first-language skills to reading comprehension in a second language is longer than the study period, the.
