A functional analysis of receptive language and productive speech: acquisition of the plural morpheme.
Understanding plurals does not make kids say them — teach talking separately.
01Research in Context
What this study did
Zeiler (1969) worked with children who had intellectual disability. The team first taught receptive plurals: when the child heard "Show me cats," they pointed to the picture with more than one cat.
Next they watched whether the child would now say "cats" on their own. No teaching or praise for talking happened during these checks. The design flipped back and forth between receptive-only training and expressive probes to see if the first skill bled into the second.
What they found
Receptive scores shot to nearly 100 % during training. Yet expressive plurals stayed at zero until the teacher added direct speaking trials.
The study showed that understanding the rule "add -s for more than one" in listening does not give the child the rule for talking. Each mode needs its own teaching.
How this fits with other research
Wilson et al. (1973) repeated the question with four children and got the same answer: three kids still needed separate productive training even after mastering receptive plurals. Their data act as a conceptual replication that strengthens the 1969 warning.
Clayborne et al. (2024) looks opposite at first glance. Their preschoolers with ASD formed equivalence classes and then used the words in new ways without extra teaching. The difference is the target: Clayborne taught broad categories, not a tiny morphological rule. Big concepts can jump modalities; small grammar bits usually don’t.
Cameron et al. (1996) found that adding word-building to reading lessons helped kids generalize to new words. Like Zeiler (1969), they showed that production practice is the key missing piece when transfer fails.
Why it matters
If you assume a child will "just start saying it" after they understand it, you may waste weeks. Probe expressive language after receptive mastery, and if the data stay flat, add direct speaking trials right away. This habit saves therapy hours and closes the gap between what the child knows and what the child can say.
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Join Free →After receptive plural trials, run five unreinforced expressive probes; if zero correct, start immediate echoic-to-tact training for the -s morpheme.
02At a glance
03Original abstract
Operant conditioning procedures were applied to two retardates to establish receptive auditory plurals: correct pointing to single or paired objects was reinforced after hearing singular or plural labels. This training proceeded until an errorless (generative) criterion of correct performance was achieved. Unreinforced probes measuring expressive use of singulars and plurals were interspersed in this receptive training. Neither subject generalized from this receptive training to expressive plurals, in that each used singulars when labeling pairs. Then, both subjects were directly trained in conventional expressive plurals to an errorless (generative) criterion. The previous design was then repeated, but the receptive repertoire was reversed: pointing at pairs in response to singular labels was reinforced, and vice-versa. Unreinforced probes of expressive plural usage again showed its independence of the current receptive repertoire in that conventional (unreversed) plural usage was displayed. Thus, the independence of the expressive repertoire (even when unreinforced) from the reinforced patterns of the receptive repertoire was demonstrated.
Journal of applied behavior analysis, 1969 · doi:10.1901/jaba.1969.2-55