The effects of differential training procedures on linked perceptual class formation.
Link two stimulus classes fastest by training the center item of one class with the edge item of the other.
01Research in Context
What this study did
Fields et al. (2007) tested four ways to link two separate stimulus classes. They used a lab matching-to-sample setup with adults. Each class held pictures that looked alike. The goal was to see which training style made the classes merge fastest.
They tried anchor-to-anchor, boundary-to-boundary, mixed pairs, and anchor-to-boundary mappings. Anchor pictures sat in the middle of a group. Boundary pictures sat on the edge. Only the anchor-to-boundary condition gave clear, strong links.
What they found
Anchor-to-boundary training won. It created the biggest, most stable linked classes. Adding other pair types on top gave an extra boost, but the anchor-boundary pair did the heavy lifting.
The authors called the extra boost synergistic: the whole was bigger than the sum of its parts.
How this fits with other research
Saunders et al. (1988) showed classes can merge without any rewards during test trials. Lanny built on that by pinning down which trained links work best.
Johnson et al. (2014) later tested adults and got mixed results: some linked classes right away, others never did. They used reinforcers as nodes, a different tactic, showing the anchor-boundary rule is not the only path.
van Schrojenstein Lantman-de Valk et al. (2006) looked at pigeons and found no sign that response patterns enter classes. That seems like a clash, but the bird study asked whether responses themselves become class members. Lanny asked which stimulus pairings link classes. Different questions, different answers.
Why it matters
When you want learners to treat two sets of items as one big concept, pair the center item from one set with the edge item from the other. Think: linking the picture of a classic dog (anchor) with the scruffiest dog picture (boundary) to create a single dog concept. Start with anchor-boundary trials, then layer on extra pairs if needed. This cuts training time and builds stronger generalization.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Pick one anchor and one boundary stimulus from each set you want linked and run conditional-discrimination trials between them first.
02At a glance
03Original abstract
When the stimuli in one perceptual class (A') become related to the stimuli in another perceptual class (B'), the two are functioning as a single linked perceptual class. A common linked perceptual class would be the sounds of a person's voice (class A') and the pictures of that person (class B'). Such classes are ubiquitous in real world settings. We describe the effects of a variety of training procedures on the formation of these classes. The results could account for the development of naturally occurring linked perceptual classes. Two perceptual classes (A' and B') were formed in Experiment 1. The endpoints of the A' class were called anchor (Aa) and boundary (Ab) stimuli. Likewise, the anchor and boundary stimuli in the B' class were represented as Ba and Bb. In Experiment 2, the A' and B' classes were linked by the establishment of one of four cross-class conditional discriminations: Aa-->Ba, Aa-->Bb, Ab-->Ba, or Ab-->Bb. Results were greatest after Aa-->Bb training, intermediate after Aa-->Ba and Ab-->Ba training, and lowest after Ab-->Bb training. Class formation was influenced by the interaction of the anchor/boundary values and the sample/comparison functions of the stimuli used in training. Experiment 3 determined whether class formation was influenced by different sets of two cross-class conditional discriminations: Aa-->Ba and Ab-->Bb, or Aa-->Bb and Ab-->Ba. Both conditions produced equivalent results. Similarities were attributable to the use of anchor stimuli as samples and boundary stimuli as comparisons in each training condition. Finally, the results afterjoint Aa-->Ba and Ab-->Bb training were much greater than those produced by summing the results of Aa-->Ba training alone and Ab-->Bb training alone. This same synergy was not observed after joint Aa-->Bb and Ab-->Ba training or either alone.
Journal of the experimental analysis of behavior, 2007 · doi:10.1901/jeab.2007.10-06