The feature-positive effect is a
very robust phenomenon described first in discrimination learning by Sainsbury
and Jenkins (1967). In concept discrimination, the "feature", the stimulus
element that defines the concept, may be present (feature-positive)
or absent (feature-negative)
In the following little lab-class
example on concept discrimination, two series of trials are provided with
identical pairs of number stimuli. Students must decide which is the "correct"
choice, with immediate feedback given. When the feature is positive, the
vast majority of students will learn the concept in ten trials. When
the feature is negative, it is a near certainty that the concept will not
be learned within 20 trials.
Unknown to the subject we are testing a Feature
Positive condition and the correct feature is "4", therefore, selecting
"A" is the correct choice. Subjects soon learn the correct response in
the Feature Positive condition (criterion: 5 consecutive correct responses).
In the Feature Negative condition, "B" would be the correct choice because
the feature "4" is absent. Under this condition few subjects learn the
correct choice.
Find out what a group of numbers have in common.
Select in each trial either group A or group B for your choice to find
the solution! Below is an example of six responses on a record sheet, although
20 trials are presented in total.
Stimulus group:
A
B
--------------------------------------------------------------------
1. B
147
239
2. A
724
639
3. A
947
865
4. A
421
795
5. A
843
261
6. A
394
756
7. .........
For more information on the term 'concept discrimination' in birds see Lea
1984; for an interesting approach to the feature-positive effect in pigeons
see also Lindenblatt and Delius 1988.
