Downloaded By: [Ingenta Content Distribution] At: 10:28 5 March 2008 Selective interference with verbal short-term memory for serial order information: A new paradigm and tests of a timing-signal hypothesis Richard Henson, Tom Hartley, and Neil Burgess Institute of Cognitive Neuroscience, University College London, London, UK Graham Hitch and Brenda Flude Lancaster University, Lancaster, UK Many recent computational models of verbal short-term memory postulate a separation between processes supporting memory for the identity of items and processes supporting memory for their serial order. Furthermore, some of these models assume that memory for serial order is supported by a timing signal. We report an attempt to find evidence for such a timing signal by comparing an “item probe” task, requiring memory for items, with a “list probe” task, requiring memory for serial order. Four experiments investigated effects of irrelevant speech, articulatory suppression, temporal grouping, and paced finger tapping on these two tasks. In Experiments 1 and 2, irrelevant speech and articulatory suppression had a greater detrimental effect on the list probe task than on the item probe task. Reaction time data indicated that the list probe task, but not the item probe task, induced serial rehearsal of items. Phonological similarity effects confirmed that both probe tasks induced phonological recoding of visual inputs. Experiment 3 showed that temporal grouping of items during list presentation improved performance on the list probe task more than on the item probe task. In Experiment 4, paced tapping had a greater detrimental effect on the list probe task than on the item probe task. However, there was no differential effect of whether tapping was to a simple or a complex rhythm. Overall, the data illustrate the utility of the item probe/list probe paradigm and provide support for models that assume memory for serial order and memory for items involve separate processes. Results are generally consistent with the timing-signal hypothesis but suggest further factors that need to be explored to distinguish it from other accounts. Requests for reprints should be sent to Richard Henson, Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK. Email: r.henson@ucl.ac.uk This work was supported by a BBSRC project grant to NB and GH. RH is supported by the Wellcome Trust. NB is supported by the Medical Research Council. We thank Nelson Cowan, Murray Maybery and an anonymous referee for their helpful comments. Graham Hitch is now at the Department of Psychology, University of York, York YO10 5DD, UK.  2003 The Experimental Psychology Society http://www.tandf.co.uk/journals/pp/02724987.html DOI:10.1080/02724980244000747 THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 2003, 56A (8), 1307–1334 Q0924—67/01