Traits and/or states
skala at INCOMA.CZ
Mon Nov 3 09:45:54 CST 2003
thank you for your explanation. Now I believe that our original point (of dr.Deleporte and me) was correct.
You seem to suppose 'states' and 'characters' to be qualitatively different in that states are (representation of) observations while characters are constructs (concepts, generalizationos...).
My position was (and is) that even 'state' is a construct - similarly to a character. You are giving an example of observing a state "five digits" which contrasts with our unability to observe "number of digits". I would like to point that even "observing five digits" is a product of information processing, often very complex. The organismal body is not naturally split into distinct perceptions that would naturally form 'states'. Our splitting of a body into perceptions is a mental process (sometimes unintentional) and the same body can be surely split into different "sets of perceptions" (or characters states). Perhaps more importantly, the observation of "five digits" is possible ONLY IF YOU ALREADY HAVE A CONCEPT OF "NUMBER OF DIGITS". (why not to observe that there are "some digits" or "a finger and 4 digits" or "more than 3 digits"...?)
1. 'states' are indeed representations of observations but not a one-to-one translations of observations. A representation is already a construction process. You can (and it is well known from taxonomic practice) make several mutually intersecting perception/state/character maps of one organism with no straighforward decision rule for which one is "right" or "false".
2. consequently, 'state' and 'character' have similar epistemic position and can be ordered with formal relations
3. state/character distinction is a way how to hierarchize these constructs in a way to make them useful for phylogenetic analysis; it is not to say that another hierarchization/ordering is impossible
skala at incoma.cz
From: Kirk Fitzhugh [mailto:kfitzhug at NHM.ORG]
Sent: Friday, October 31, 2003 8:31 PM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: Traits and/or states
At 10:42 AM 10/31/03 +0100, you wrote:
>The character/state distinction seems to be (to me, at least) reasonable
>not only from the purely practical point of view.
>What we call 'character' and 'state' in the phylogenetic analysis are
>indeed both high-level constructs, not observations (not speaking about
>all the problems with the process of "observation"). The character/state
>distinction is a way how to hierarchize such constructs; we can treat this
>hierarchic relation as a subject/predicate, variable/value or whatever but
>the language we are using can hardly change the merit. I have personally
>found nothing in your message (nor in your presentation referenced below)
>what would contradict this generally accepted opinion. Perhaps you could
>explain your position in more detail?
My thanks to Drs. Skala and Deleporte for their thoughtful comments. I will
try to respond here to both.
I'm not entirely sure I understand what is meant by "high-level
constructs." If descriptions of organisms, or the cells of a data matrix,
do not represent our observations, then it would be difficult to claim that
a phylogenetic hypothesis is an explanation of shared similarities.
The concern I have had with the "character" and "state" distinction is that
it is not consistent with the nature of observation. What we observe are
objects by way of their properties (= character, attribute, trait), and
these are communicated by subject-predicate relations. For instance, I
cannot observe "number of digits." But I can observe that the distal ends
of some set of appendages (subject) have five digits (predicate). The
"character," "number of digits," and the "state," "five," cannot represent
subject-predicate relations denoting observations since "number of digits"
does not represent the subject observed. What are observed are subjects
called appendages with the property (= character, attribute, trait) of five
digits. The cell of a data matrix for species X must code the observation
that individuals in this class have appendages with five digits. The cell
is not simply a "state;" the cell summarizes observations.
I don't find any hierarchic relation here, and such a relation would not be
expected for objects and their properties. On the other hand, an object can
be composed of subsidiary objects, in which case hierarchic relations can
be stated. But, this hierarchic relation of a part composed of parts is not
equivalent to the observations which allow us to speak of the relation itself.
I hope this helps clarify what I said earlier.
J. Kirk Fitzhugh, Ph.D.
Associate Curator of Polychaetes
Invertebrate Zoology Section
Research & Collections Branch
Los Angeles County Museum of Natural History
900 Exposition Blvd
Los Angeles CA 90007
e-mail: kfitzhug at nhm.org
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