Did the boy bite the cat, or was it the other way around?
When processing a sentence with several objects, one has to establish ‘who did what to whom’. When a sentence cannot be interpreted by recalling an image from memory, we rely on voluntary imagination to construct a novel mental image in our mind.
In a previous study, the team of Dr. Andrey Vyshedskiy, a neuroscientist from Boston University, USA, hypothesized that this voluntary imagination ability has fundamental importance for combinatorial language acquisition. To test the hypothesis, the researchers designed a voluntary imagination intervention and administered it to 6,454 children with language deficiencies (age 2 to 12 years).
In that three-year study, published in 2021, the scientists concluded that children, who were engaged with the voluntary imagination intervention, showed 2.2-fold improvement in combinatorial language comprehension compared to children with similar language deficiencies. These findings suggested that language can be improved by training voluntary imagination and confirmed the importance of the visuospatial component of language.
In his latest work, now published in the open-science scholarly journal Research Ideas and Outcomes (RIO), Dr. Vyshedskiy builds on these experimental findings to address the question of language evolution and suggest that evolutionary acquisition of language was driven primarily by improvements of voluntary imagination, rather than the speech apparatus.
Dr. Vyshedskiy proposes that this step-wise development of voluntary imagination – and not the speech apparatus per se – was the key factor underlying the acquisition of modern combinatorial language.
There are several additional lines of evidence suggesting dissociation of articulate speech and voluntary imagination.
Firstly, there is significant genetic and archeological evidence that modern speech apparatus was acquired 600,000 years ago, which is quite a long time before acquisition of modern voluntary imagination 70,000 years ago.
Secondly, mirroring phylogenetic sequences, typical children develop articulate speech by their second year, two years before they acquire the voluntary imagination necessary to comprehend spatial prepositions, recursion, and complex fairy tales.
Thirdly, speech is not an obligatory component of combinatorial language at all. If early humans had voluntary imagination, they could have invented sign language. All formal sign languages include spatial prepositions and other recursive elements. This has been evidenced in the 1970s, when the largest natural experiment of language origin to date reported on 400 Nicaraguan deaf children from two schools who spontaneously invented a new combinatorial sign language in just a few generations. This means that the capacities of the speech apparatus could not have been a limiting factor in the acquisition of modern combinatorial language at all.
Fourthly, articulate sounds can be generated by gray parrots and thousands of other songbird species. However, these birds do not acquire combinatorial language. So, evolution of sound articulation is independent from and also a simpler process than improving voluntary imagination.
In conclusion, on the basis of children studies, neurological observations, archeological findings, combinatorial sign language invention by Nicaraguan deaf children, and variety of sound boxes in birds, Dr. Vyshedskiy argues that the evolution of hominin speech apparatus must have followed (rather than led to) the improvements in voluntary imagination.
Contrary to the common assumption, it is voluntary imagination rather than speech that appears to define the pace of combinatorial language evolution.
Vyshedskiy A (2022) Language evolution is not limited to speech acquisition: a large study of language development in children with language deficits highlights the importance of the voluntary imagination component of language. Research Ideas and Outcomes 8: e86401. https://doi.org/10.3897/rio.8.e86401