Subject: perceptual variables and data variables From: Stephen Barrass <stephen.barrass(at)GMD.DE> Date: Mon, 31 Aug 1998 12:25:52 +0200Al Bregman says > A dimension of > experience, such as pitch, can be either prothetic or metathetic > (metathetic, in the case of pitch). The mass of an animal is physical,= so > it can't be either prothetic or metathetic. > > It occurred to me that if we're not allowed to link quantitative physic= al > variables such as wavelength or repetition rate with metathetic variabl= es > of experience, such as color or pitch, psychophysics (i.e., Psycho <-- > physics) becomes impossible. > in visualization Bertin has proposed a formal method for representing data variables with perceptual variables the idea is that a prothetic variable such as colour lightness or sound loudness which has a true or "natural" zero and a unidimensional metric (i.e. colour can't be seen when lightness goes to zero, sound can't be heard when loudness goes to zero) allows faster, more accurate perceptions of ratio data (i.e. data with a true zero and a unidimensional metric such as the mass of an animal) metathetic variables such as colour hue, allow the better perception of difference without order in judgements of difference between categorical data (for example different colours for different species of animals in a graph) pitch has order and difference, but no zero so allows better perception of ordinal data (for example ordered categories such as the likelihood of rain classed as "low, medium or high") further reading if interested ... Bertin J. (1981) Graphics and Graphic Information Processing, Walter de Gruyter. Casner S. (1992) A Task Analytic Approach to the Automated Design of Graphic Presentations, ACM Transactions on Graphics, 10, pp 111-151. Cleveland W.S. (1985) The Elements of Graphing Data, Wadsworth Advanced Books and Software, Monterey, California. Norman D.A. (1991) Cognitive Artifacts, in Carroll J.M. (ed), Designing Interaction : Psychology at the Human-Computer Interface, Cambridge University Press. Rogowitz B.E. and Treinish L.A. (1993a) Data Structures and Perceptual Structures, Proceedings of the SPIE Human Vision, Visual Processing and Digital Display IV, SPIE Vol. 1913. Ware C. (1993) The Foundations of Experimental Semiotics: a Theory of Sensory and Conventional Representation, Journal of Visual Languages and Computing, 4, pp 91-100, Academic Press Limited, London. -- Gr=FC=DFen stephen Stephen Barrass Ph.D. <http://viswiz.gmd.de/~barrass/thesis/> Virtual Environments <http://viswiz.gmd.de> GMD IMK, Schloss Birlinghoven, D-53754 St. Augustin, Germany fax:+49-2241-14-2040 phone:+49-2241-14-2838(w) +49-0228-465432(h) Email to AUDITORY should now be sent to AUDITORY(at)lists.mcgill.ca LISTSERV commands should be sent to listserv(at)lists.mcgill.ca Information is available on the WEB at http://www.mcgill.ca/cc/listserv