Carston was born in New Zealand.[2] She studied English literature at the University of Canterbury, graduating with a Bachelor of Arts (BA) 1975.[3] She then studied for an honours degree in linguistics at Victoria University of Wellington, graduating with a BA (Hons) degree in 1976.[3] She moved to England to study at University College London (UCL), graduating with a Master of Arts (MA) with Distinction in Phonetics and Linguistics in 1980.[3] She remained at UCL to undertake postgraduate research under the supervision of Deirdre Wilson.[2][3] and got her first job as a lecturer there in 1983. She completed her Doctor of Philosophy (PhD) degree in 1994.[3] Her doctoral thesis was titled "Pragmatics and the explicit/implicit distinction".[4]