Speech Research Group


Prof Peter Howell

Prof Peter Howell


Department of Psychology
University College


  • Professor of Experimental Psychology
    Experimental Psychology
    Div of Psychology & Lang Sciences

Joined UCL


My current research involves developing and testing an account of why stuttering persists in some speakers whilst other speakers recover. EXPLAN theory maintains that there are two distinct components involved when producing speech: linguistic processing (called planning) and motor programming (termed execution).

According to the theory speakers start an utterance by planning the linguistic component of the first element in the intended sequence and, once this is complete, they pass it on to motor programming after which speech output results (execution). Planning the next element takes place concurrent with execution of the current plan. Speech is fluent when there is sufficient time during motor programming of one plan for the next one to be generated. Speech is dysfluent if the next plan is not ready. This is most likely to happen when the previous word takes a short time to execute and the next word takes a long time to plan. Consequently, fluency problems arise at the junction of easy/ hard words (function/content, unstressed/stressed, high frequency/low frequency etc.). The relative difficulty of the material at these points determine fluency. According to EXPLAN there are two ways of dealing with this situation: One is to repeat already-completed motor plans or hesitate speech at the juncture (called collectively stalling). This results in pausing or whole word repetition on one or more words (when they are called phrase repetitions) before a difficult word. Stalling slows speech execution rate. The other way to deal with the problem at the juncture is to generate speech output using the completed part of the linguistic plan on the difficult word. As only part of the plan is available, this leads to breakdown when the plan runs out. This brief overview indicates three elements are important in EXPLAN - planning, execution and the interface between them.


Some of the main achievements with respect to stuttering in addition to the model are: discovery of the fluency-enhancing effects of frequency altered feedback that is used in prosthetic devices with people who stutter; a model that predicts which children will persist and which children will recover from stuttering, a major longitudinal project on children who stutter which identified several previously unknown risk factors for stuttering, the world’s first online archive of stuttered speech, estimates of heritability of stuttering, scanning work to identify functional and structural factors in stuttering and child and parent expectations about treatment for stuttering.


My current research on stuttering is focusing on motor learning in people who stutter, development of a model for screening unselected school children for stuttering and other communication disorders and the impact of language usage factors on stuttering. The motor learning work involves training English speakers on tone contrasts and seeing how brain activity changes during this process. Control work for this (including scanning) as well as parallel studies training Chinese speakers on Western speech sounds they do not know is taking place in Beijing with Dr Chunming Lu (I am a visiting professor at Beijing Normal University).    


Award year Qualification Institution
1983 PhD
Doctor of Philosophy
University College London
1972 BSc Hons
Bachelor of Science (Honours)
Sociology and Psychology
University of Bradford

After graduating with a degree in Psychology and Sociology, I worked as a research assistant at UCL under Professor Robert Audley. When that grant finished I worked as a programmer at Sussex University with Professor Chris Darwin. Chris got me interested in speech. Subsequently I returned to UCL to do my PhD (supervised by Prof Audley) on speech perception. On completion of my PhD, I joined the staff at UCL and have been here ever since. I branched out into speech production, looking at the relationship between speech perception and production with Nigel Harvey. As part of this work I examined auditory feedback processes which eventually led me to investigate stuttering (see Research summary). I developed allied interests in hearing (with Stuart Rosen) and music (with Ian Cross and Rob West). I have benefitted from collaborations with many colleagues in psychology and speech science over the years and this continues now we are all part of the PALS division. I have played an important role in internationalizing awareness and setting up research facilities in several parts of the world. Some of the main ones are Iran where I published a handbook on stuttering in Farsi (supported by British Council grants), Beijing (you can read more about this under research interests), Japan, Brazil, parts of Western Africa and most recently in the middle east (Jordan, Pakistan and Qatar).My fervent wish when working with students is to spark them to get as interested in understanding speech processes and how it can go wrong as I am.


Ageing|*|Angelman syndrome|*|Anxiety|*|Anxiety disorders|*|Aphasia|*|Apraxias|*|Attention|*|Auditory|*|Auditory processing|*|Autism|*|Autism spectrum disorders|*|Basal ganglia|*|Behavioural analysis|*|Brain|*|Brain imaging|*|Brain injury|*|Cerebellum|*|Cognition|*|Cognitive|*|Computational methods|*|Computational modeling|*|Computational modelling|*|Computational models|*|Congenital disorders of cerebral cortical development|*|Deafness|*|Decision|*|Decision making|*|Development|*|Diffusion tensor imaging (DTI)|*|Drug abuse - neurological consequences|*|Dyspraxia|*|Dystonia|*|FMRI|*|Fragile X syndrome|*|Functional MRI (fMRI)|*|Genetic screens|*|Head trauma|*|Hearing|*|Hearing and balance|*|Language Modelling|*|Motor control|*|Movement disorders|*|Neurodegenerative diseases|*|Neuropsychological testing|*|Neuropsychology|*|Neuroscience|*|Operant conditioning|*|Parkinson's disease|*|Perception|*|Personality disorders|*|Plasticity|*|Psychoacoustics|*|Psychometrics|*|Psychophysics|*|Randomized Controlled Trials (RCTs)|*|Speech|*|Speech production|*|Stroke|*|Tourette syndrome|*|hearing|*|perception