Derivational morphology and suffixing bias on linguistic and nonlinguistic material

Across world languages, grammatical meanings tend to be expressed by suffixes. Whether this bias is defined by shaping language so that it is easily processed by domain-general cognitive mechanisms or whether the bias is specific to the language domain has not been resolved. Most evidence supporting these competing hypotheses focuses on the effect of suffixing bias on inflectional morphology and ignores derivational morphology. Here, we explored suffixing bias in German and Slovak populations. These languages are strongly suffixing in terms of inflectional morphology but differ in verbal derivational morphology. Verbal prefixes can be detached from the root in the German language and are always attached to the root in the Slovak language. We explored whether suffixing bias can be observed in both populations while detecting and memorizing linguistic and nonlinguistic sequences in a continuous sensory input by means of statistical learning mechanisms. We found that suffixes facilitate statistical learning more than prefixes on linguistic material, and the effect was not observed on nonlinguistic material, suggesting that suffixing bias is specific to speech. When people are forced to choose between suffixed and prefixed sequences from the familiarization stream, German speakers show a stronger preference for suffixed sequences, while Slovak speakers do not show any preference; hence, properties of derivational morphology of the ambient language can modulate suffixing bias.