Subject: Unattended streams From: Al Bregman <BREGMAN(at)PSYCH.MCGILL.CA> Date: Fri, 25 May 2001 10:51:38 -0400Dear Michael, I believe you are right to argue that the background streams are at least partially organized, but it's a hard question to attack experimentally. You may have given a hint as to how to go about it when you wrote: "you can switch attention from a foreground stream A to one of a pair of background streams B and C in less time than it takes for two streams to form from B and C without A (though I haven't found a published ref for this)." In other words, we know that it takes time (T) for a stream to form. If switching attention allows the system to skip the T interval, it suggests that the switched-to stream was already formed. So far as I know, the only person to attack this problem by getting subjects to switch streams is Bob Carlyon. His results seem to imply that there is no (background) stream until the switch occurs. [Bob, is there an online version of your article that interested persons could read?] His results seem to be at odds with Elyse Sussman's findings with evoked potentials (method of mismatch negativity) that show that an unattended stream still evinces "surprise" when the order (but not the identities) of tones in the stream changes. It is hard to reconcile these two findings as well as the everyday experience recounted by you. Clearly more thinking and research are in order. Al ---------------------------------------------------------------- Albert S. Bregman, Emeritus Professor Psychology Dept., McGill University 1205 Docteur Penfield Avenue Montreal, QC, CANADA H3A 1B1 Office: Tel: +1 (514) 398-6103 Fax:+1 (514) 398-4986 Home: Fax & phone: +1 (514) 484-2592 Lab web page: www.psych.mcgill.ca/labs/auditory/laboratory.html ----------------------------------------------------------------- - Michael Norris wrote: > Has anyone looked into what qualities of the organization of unattended > streams differ from the attended stream? I believe that the background > streams are organized to some extent because (from my own informal > experiments) you can switch attention from a foreground stream A to one > of a pair of background streams B and C in less time than it takes for > two streams to form from B and C without A (though I haven't found a > published ref for this). The question then is in what ways are the > background streams less organized than the foreground? > > -m. ------------------------------------------------- Albert S. Bregman, Emeritus Professor Dept of Psychology, McGill University 1205 Docteur Penfield Avenue Montreal, QC, Canada H3A 1B1 Office: Phone: +1 (514) 398-6103 Fax: +1 (514) 398-4896 Home: Phone & Fax: +1 (514) 484-2592 Email: bregman(at)psych.mcgill.ca -------------------------------------------------