The Mechanism Of Irrelevant Speech Effect On Text Reading:What Role For The Nature Of Text Processing

Text reading is vulnerable to disruption by sound in our daily life,particularly if that sound is speech.The phenomenon that task-irrelevant background sounds disrupt performance of visually-based cognitive tasks is typically termed as the Irrelevant Speech Effect(ISE).Studies on the short-term memory have demonstrated that identical irrelevant speech can produce different effects in list recall due to the different task demands,suggesting the auditory distraction in short-term memory is process-oriented.However,there is currently no published research that has directly manipulated task demands during reading and we know little of whether the disruption by background speech on reading is jointly dependent on the nature of the sound and the task processes deployedThe present research conducted a series of five experiments to investigate the role of focal task processing in the ISE by exploiting the combination of behavioural measures and eye-tracking techniquesTo specify the properties of background speech that determine disruption to reading,in Experiment 1,participants either read sentences while being exposed to Chinese speech,scrambled-character speech(meaningful in character level),Uyghur speech(unintelligible for the participants),pink noise or silence.The results showed that Chineses speech and scrambled-character speech increased fixations,regressions,average fixation duration,regression path and total reading times compared to silence.However,there were no difference for Uyghur speech,pink noise or silence conditions.The findings could be explained by both semantic-interfenece-by-content hypothesis and interference-by-process hypothesisExperiment 2 investigated whether the disruption of text reading by background speech was jointly-dependent on the meaningfulness of the background speech and the demands for semantic processing in the focal task.The meaningfulness of speech was manipulated by comparing Chinese speech and Uyghur speech.Two focal,reading tasks differ only in their processing requirements.In one task,participants were required to adjudicate whether the sentence made sense(i.e.,semantic acceptability task)and in the other task,another group of participants were required to identify whether the sentence contained a noncharacter(i.e.,non-character detection task).Results showed a substantial disruptive effect of the meaningfulness of the speech only in the semantic acceptability task.Compared with reading with meaningless speech or reading in silence,the meaningful speech increased numbers of fixations,regressions,regression path and total reading times.These results favoured the interference-by-process hypothesis over interference-by-content hypothesisThus,one striking aspect of the present findings and most previous studies was that phonological properties of speech have little influence on text reading.Notably,the absent effect by the phonological properties of speech on reading seems to be conflict with both the interference-by-content and the interference-by-process hypotheses.To further verify the interference-by-process hypothesis from the perspective of phonological processing,the next three experiments examined whether the disruption of text reading by background speech would be jointly-dependent on the phonological properties of the background speech and the demands for phonological processing in the focal task.The semantic properties of speech were manipulated by comparing normal Chinese speech and phonotactically-legal meaningless speech(PLS).Whilst the phonological properties of speech were manipulated by comparing PLS and spectrally-rotated speech(SRS)Experiment 3 also adopted two task demands to manupilate the nature of the focal task processing in the character level.Participants were instructed to decide whether the presented character pair shared the same meaning or onset under the semantic decision task and the phonological decision task,respectively.The results were very straightforward and clear,showing that the meaningfulness of speech only increased participants' reaction times in the semantic decision task and the phonological properties of speech only increased participants'reactions times in the phonological decision taskExperiment 4 used sentences with repeated phonemes and matched normal sentences as reading materials.The results showed that both semantic and phonological properties of speech disrupted two types of sentence reading.The difference is that the semantic properties of speech affected two sentence conditions similarly.Whilst the phonological properties of speech exerted a more significant disruption on sentences with repeated phonemes than normal sentences.Experiment 5 adopted two task demands to manupilate the nature of the focal task processing in the sentence level.The sentences to be read were the same set of sentences with repeated phonemes in Experiment 4.For one group,participants were required to read the sentence for meaning and then answer a short "yes-no" question(i.e.,semantic decision task)For another,participants were required to find the most frequent onset in the sentence and then choose one character contained that onset out of two characters(i.e.,phonological decision task).The results showed that the semantic properties of speech only disrupted the semantic decision task.However,the phonological properties of speech influenced both tasks,producing more disruption on the phonological decision task than the semantic decision task.The findings from the above three experiments implied that the phonological content of speech would also affect text reading,especially when the focal tasks emphasize phonological processingTaken together,the present research provides the first well controlled demonstration of a modulatory influence of focal task-process on disruption caused by speech during text reading Our primary conclusion from these results is that the extent to which auditory distraction effects occur in a reading situation depends both on the nature of the distraction sounds and the precise task that the participant is engaged in,which is best explained by the interference-by-process hypothesis.