Many people think adults cannot change their English pronunciation. Research says this is not true. Scientists looked at 86 studies about pronunciation lessons, and the lessons worked very well. They helped more when they were long and when teachers corrected the students.

But many tests asked students to read sentences aloud. When students spoke freely, the changes were harder to see. So practice your sounds with help, and then try to use them when you talk.

Adults are commonly told that they cannot improve their pronunciation, but research disagrees. In 2015, a team of applied linguists combined the results of 86 studies on pronunciation teaching and found a large average effect. Lessons worked better when they lasted longer, when learners received feedback, and when tests were controlled, such as reading sentences aloud.

However, another review of 75 studies pointed out that very few researchers measured spontaneous speech. In one experiment, 20 Japanese learners became easier to understand when reading sentences after only four hours of lessons, but their accent did not clearly become weaker. This shows that being understood and sounding like a native speaker are different goals. Learners should practice target sounds with feedback and then use them in free conversation.

Adult pronunciation is often said to be fixed for life, but the research says otherwise. A 2015 meta-analysis of 86 reports found that pronunciation instruction produced a large average effect, with stronger gains for longer programs, for treatments that included feedback, and for controlled outcome measures. That last point, however, deserves attention.

A narrative review of 75 studies published the same year showed that reading aloud was the most common way of measuring progress, while spontaneous speech was rarely tested. When Saito and Plonsky later reclassified the measures used in 77 studies, instruction appeared most effective when learners could carefully monitor specific sounds, whereas gains in free speech judged holistically by listeners were not clearly shown.

Individual studies point in a similar direction. Twenty Japanese learners who received four hours of instruction on difficult consonants and vowels became more comprehensible when reading sentences, yet their perceived accent did not significantly decrease. In contrast, Chinese university students taught stress, rhythm and intonation for 18 weeks improved in spontaneous speech as well. Pronunciation teaching works, but carrying the gains over into real conversation takes deliberate practice beyond the script.