Fox Tree showed that collateral signals are essential to successful communication in everyday situations and are beneficial to listeners.
Rather than unwanted errors, Fox Tree's research has shown that collateral signals are actually meaningful and relevant to both speaker and listener, and that removing them from speech can negatively effect comprehension.
This view counters that proposed by Noam Chomsky, the well-known linguist from MIT who regarded such utterances as errors in performance and not part of proper language.
[1] Fox Tree published two articles with Herb Clark, Professor of Psychology at Stanford University.
In one paper, Clark and Fox Tree (2002)[2] argued that 'uh' and 'um' are conventional English words that speakers use in distinct ways.