I did not see your earlier query, or possibly zapped it without reading...
you may be interested in:
 
"What Visitors Want to Know: The use of front-end and formative
evaluation in determining label content in an art museum," for openers,
by Lisa Hubbel Mackinney, June, 1993 Master of Arts paper for the School
of Liberal and Professional Arts at John F. Kennedy University
 
Also, anything written by Beverly Serrell of Serrell and Assoc. out
of Chicago; there's also an AAM publication; also, refer to AAM publication put
 out via N.A.M.E. (standing committee on exhibitions), called "Recent and
Recommended," which is a bibliography of outstanding sources relating to
signs, wayfinding, label design and fabrication, exh. design, and other good
stuff...
 
The Masters paper summarizes many other studies about labels..
 
Hope this helps:
T. Robinson
The Detroit Institute of Arts
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