Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!cs.utexas.edu!rutgers!njin!princeton!pucc!PSYCH@TCSVM From: harnad@phoenix.Princeton.EDU (Stevan Harnad) Newsgroups: sci.psychology.digest Subject: PSYCOLOQUY V1 #9 (discussion : 162 lines) Message-ID: <9007191824.AA01816@reason.Princeton.EDU> Date: 18 Jul 90 20:55:59 GMT Sender: VMNNPOST@pucc.Princeton.EDU (Listserv to Netnews Gateway) Organization: Listserv to Netnews Gateway at pucc.Princeton.EDU Lines: 157 Approved: PSYCH@TCSVM PSYCOLOQUY Wed, 18 Jul 90 Volume 1 : Issue 9 Lateralized and Central Presentations in Neuropsychology Memory ---------------------------------------------------------------------- From: Bob Zenhausern Subject: Lateralized and Central Presentations in Neuropsychology I would like to continue developing the ideas initiated in these two short excerpts. For example, I have empirical data using central presentation that shows that the sex difference in laterality is due to a decrement in right hemisphere presentation for males, rather than a "left hemisphere superiority". Another point I would like to develop is an explanation of lateralized differences on the basis of integrated functioning. The whole brain is needed for the task, but when the stimulus is lateralized the "quality" of what one hemisphere passes to the other toward this integration varies and this difference is the basis of lateralized differences in performance. I would appreciate any reactions to this series and suggestions as to the best way to present it for general discussion. Bob Zenhausern drz@sjuvm This is the first in a series of ideas on lateralized presentations in neuropsychology that will focus on an integrated rather than split brain approach. Too much of the literature is written from a split brain perspective, as can be seen from statements such as: "The left hemisphere does the task more efficiently than the right hemisphere." This wording is misleading and makes inferences far beyond the data. Any task presented to an intact individual must be completed through the integrated functioning of the whole brain and lateralizing the stimulus does not change this fact. The more conservative statement would be: "The subject performed the task more efficiently when the stimulus was presented to the left hemisphere than when it was presented to the right hemisphere." This latter statement is about an observable fact; the former is much more speculative. The next question is "Why is performance better with left hemisphere presentation?" The question can only begun to be answered if an essential control condition -- central presentation -- is included. Lateralization is a distortion of normal perception and the effect of this distortion can only be examined in comparison to normal non-lateralized presentation. Unfortunately, it is rare for a study investigating laterality to include such central presentation as this essential control condition. Here is a concrete (albeit fictitious) example. Consider these hypothetical experiments examining lateralized differences in accuracy to three "verbal tasks". LH RH Experiment 1 50 40 Experiment 2 50 40 Experiment 3 50 40 On the basis of these results one could conclude that the effect of lateralizing the stimulus was equal for all 3 tasks. However, to these hypothetical results, add equally hypothetical scores from a central presentation condition and three entirely different interpretations emerge. Experiment 1 Central = 100. Conclusion: The effects of lateralizing the stimulus are far more critical than left/right differences. Experiment 2. Central = 50. Conclusion: There was a right hemisphere decrement due to lateralization. Experiment 3. Central = 40. Conclusion: There was a left hemisphere facilitation due to lateralization. I now want to present actual data from a recent PH.D. dissertation here at St. John's. It was a reaction time study comparing males and females on a lateralized task. The table below represents a significant interaction effect. Left Hem Right Hem Central Males 820 840 810 Females 852 852 834 Without the Central condition, it would seem that males were faster with Left Hem than Right Hem presentation, but there was no difference for females, leading to the familiar conclusion that males are more lateralized than females. The Central condition makes it clear, however, that lateralized presentation resulted in an overall performance decrement and the male "left hemisphere advantage" was in fact due to a greater decrement in performance with right hemisphere presentation. The females show equal decrements for the two hemispheres. Rather than saying males are more lateralized than females, might it be more accurate to say that females are more integrated than males since performance does not depend on the hemisphere to which the stimulus was lateralized? Bob Zenhausern drz@sjuvm ------------------------------ From: Frank Dane Subject: Memory During a discussion on a different list, someone posed the following: >>Linda Weltner, a writer for The Boston Globe, wrote an _excel- lent_ commentary on this a year or so (see, what I mean!) ago. She vividly describes how one is racing along in a conversation, bringing in witty and incisive tidbits of information, and suddenly, WHAM!, some key item you need is just not there. Resort to cute mnemonic tricks won't retrieve it, it just isn't there at that moment, though it will bob to the surface later. Everyone in the 40-50 age range that I have showed this to, has said, "Yes, yes! Exactly!" So, I return to my original speculation. Has anyone bothered to study this? Do the studies bear out the anecdotal evidence? Is this something that has always existed, but is just much, much more noticible in an information age?<< Memory is not my area. Does anyone have any suggestions vis-a- vis specific research? Frank Dane, Mercer University ------------------------------ PSYCOLOQUY is sponsored by the Science Directorate of the American Psychological Association (202) 955-7653 Co-Editors: (scientific discussion) (professional/clinical discussion) Stevan Harnad Perry London Psychology Department Dean, Graduate School of Princeton University Applied and Professional Psychology Rutgers University Assistant Editors: Malcolm Bauer John Pizutelli Psychology Department Psychology Department Princeton University Rutgers University End of PSYCOLOQUY Digest ******************************