Teresa Pica (1945–2011) was Professor of Education at the University of Pennsylvania Graduate School of Education from 1983 until her death, and one of the researchers who turned the Interaction Hypothesis from a Long-and-Varonis slogan into a mature empirical programme. She came to SLA sideways: first a speech-language pathologist running a pre-school language stimulation programme at the Child Development Center in Mount Vernon, New York, then into applied linguistics.
Her extension of interaction research centred on negotiation of meaning as a function of task type and participant relationship. Symmetric, information-gap, outcome-required tasks generate more negotiation, she argued, and negotiation is where comprehensible input, modified output, and noticing all converge. Her 1994 Language Learning review "Research on Negotiation" is the standard reference, and much of today's TBLT research literature sits on her classifications of task type. She supervised more than fifty doctoral dissertations at Penn, including Jessica Williams and Catherine Doughty.