Fields, L., Reeve, K. F., Adams, B. J., Brown, J. L., & Verhave, T. (1997).
Predicting the extension of equivalence classes from primary generalization gradients: The merger of equivalence classes and perceptual classes.
Journal of the Experimental Analysis of Behavior,
68, 67-91.
In Experiment 1, 6 college students were given generalization
tests using 25 line lengths as samples with a long line, a short
line, and a "neither" option as comparisons. The
neither option was to be used if a sample did not go with the
other comparisons. Then, four-member equivalence classes were
formed. Class 1 included three nonsense words and the short line.
Class 2 included three other nonsense words and the long line.
After repeating the generalization test for line length,
additional tests were conducted using members of the equivalence
classes (i.e., nonsense words and lines) as comparisons and
intermediate-length lines as samples. All Class 2 comparisons
were selected in the presence of the test lines that also evoked
the selection of the long line in the generalization test that
had been given before equivalence class formation. Class 1
yielded complementary findings. Thus, the preclass primary
generalization gradient predicted which test lines acted as
members of each equivalence class. Regardless of using
comparisons that were nonsense words or lines, the
post-class-formation gradients overlapped, showing the
substitutability of class members. Experiment 2 assessed the
discriminability of the intermediate-length test lines from the
Class 1 (shortest) and Class 2 (longest) lines. The test lines
that functioned as members of an equivalence class were
discriminable from the line that was a member of the same class
by training. Thus, these test lines also acted as members of a
dimensionally defined class of "long" or
"ort" lines. Extension of an equivalence class, then,
involved its merger with a dimensionally defined class, which
converted a close-ended class to an open-ended class. These data
suggest a means of predicting class membership in naturally
occurring categories.
Key words: equivalence classes, generalization of emergent
relations, perceptual classes, class merger, discriminability,
key press, human adult