The Effects and Interactions of Top-down Influences on Word Recognition

It is widely acknowledged that top-down influences such as our prior experiences, expectations and knowledge influence the way in which we perceive information. However less attention has been given to how different sources of top-down influences interact when modifying sensory information. In this study we utilised concurrent behavioural and EEG measurements to examine the main effects and interactions of two sources of expectations - informative hints (semantic priming), and stimulus repetition - in an auditory task requiring the recognition of spoken words embedded in noise. We manipulated participants’ prior knowledge of the target stimuli by presenting valid, invalid and no hints (both acoustically and visually), and then assessed how their performance differed over multiple repetition blocks. Although we found an initial effect of informative hints, these effects were short lived and did not carry on to later repetition blocks. Contrastingly, the effect of repetition-based learning was more robust, and quantitatively overrode the effects of hint types and modalities in which they were delivered. While the interactive effects between hints and repetitions were also observed, they were not consistent across hint types and modalities. Taken together, we argue that both informative hints and stimulus repetition might utilise different learning mechanisms, both of which contribute to the perception of speech.