Implicature processing
When we speak, we often communicate, implicitly, much more than what we say literally. For instance, if you ask your friends whether they liked the dinner you prepared, and they reply “Some of your dishes were nice,” you will understand that, most probably, they did not like all the dishes - even though this was not what they literally told you.
Understanding meaning that is not explicitly expressed, as in the example above, requires making an inference (an “implicature”). Is making these implicatures more difficult than sticking to the literal meaning of sentences?
To answer this question, we reasoned that if implicatures are mentally effortful, they could be particularly challenging for children's developing mind and for non-native speakers. Our results confirmed this: Both these groups prefer to interpret sentences more literally than adult native speakers do.
We then focused on autism, because autistic individuals are often said to understand language literally. In an experiment, we measured participants’ eye pupils while they made implicatures, because pupils change involuntarily not only with light, but also with mental effort. Interestingly, individuals with fewer autistic traits showed smaller pupils while making the implicature, indicating that they were making less effort when doing so.
The dissertation shows that implicatures, despite being ubiquitous in everyday language, are mentally effortful, and pupils offer a window into the hidden mental cost of implicit language.