Date Published: March 22, 2016
Publisher: Public Library of Science
Author(s): Jukka Hyönä, Miia Ekholm, Kevin Paterson.
Effects of background speech on reading were examined by playing aloud different types of background speech, while participants read long, syntactically complex and less complex sentences embedded in text. Readers’ eye movement patterns were used to study online sentence comprehension. Effects of background speech were primarily seen in rereading time. In Experiment 1, foreign-language background speech did not disrupt sentence processing. Experiment 2 demonstrated robust disruption in reading as a result of semantically and syntactically anomalous scrambled background speech preserving normal sentence-like intonation. Scrambled speech that was constructed from the text to-be read did not disrupt reading more than scrambled speech constructed from a different, semantically unrelated text. Experiment 3 showed that scrambled speech exacerbated the syntactic complexity effect more than coherent background speech, which also interfered with reading. Experiment 4 demonstrated that both semantically and syntactically anomalous speech produced no more disruption in reading than semantically anomalous but syntactically correct background speech. The pattern of results is best explained by a semantic account that stresses the importance of similarity in semantic processing, but not similarity in semantic content, between the reading task and background speech.
Reading is done in many different physical environments. It may be done during a quiet evening lying on a couch undisturbed by any external sources of visual or auditory information. It may also be done in a noisy environment, such as a crowded cafeteria or a busy train or subway couch, where a lively discussion or a phone conversation may be heard in the background. Many people prefer to read in silence and find noisy environments distracting and disturbing for reading.
In Experiment 1, reading of long sentences embedded in text was tested in three different background speech conditions: in silence, with Italian background speech (non-meaningful to the participants), and with Finnish background speech (meaningful to the participants). Based on the phonological loop model , it was hypothesized that if phonological loop is in operation during the comprehension of long, syntactically complex sentences, sentence processing is disrupted by the presence of background speech, in comparison to the silent condition, regardless of the meaningfulness of the background speech (yet, meaningful background speech may disrupt more than meaningless background speech). The model further predicts a more robust syntactic complexity effect during the two irrelevant speech conditions compared to the silent condition. This prediction is based on the assumption that syntactic complexity increases the comprehender’s reliance on the contents of the phonological short-term store  and that irrelevant speech corrupts or overwrites its contents so that the verbatim representation of the initial constituent of the main clause will be lost by the time the reader encounters the rest of the main clause. This loss is assumed to be more detrimental to the processing of complex than less complex sentence constructions. On the other hand, the view advocated by Sörqvist and Marsh  does not predict such an effect, as processing difficulty is assumed to shield against distraction by task-irrelevant stimuli.
On the basis of the interference-by process account of auditory distraction of Marsh et al. (2008), it may be argued that disruption in reading comprehension due to irrelevant background speech is caused by the two information sources (written text and background speech) calling for and activating shared semantic representations and processes. In the Introduction, we sketched an analogous account for syntactic information. According to this account, shared syntactic representations and processes between the text to-be-read and the background speech would be responsible for the disruption effects in reading.
The first goal of Experiment 3 was to re-examine whether it is indeed the case that coherent speech would not lead to marked disruption in reading, compared to silence, as observed in Experiment 1. The second aim of Experiment 3 was to directly compare disruption effects by meaningful speech (Experiment 1) to those of scrambled speech obtained in Experiment 2 (both semantically unrelated to the text to be read). Experiment 1 suggested that coherent irrelevant speech does not interfere markedly with sentence parsing, while Experiment 2 provided evidence for notable disruption in sentence processing due to anomalous background speech. In Experiment 3, we pitted these two background speech conditions against each other as a within-participants comparison. More robust interference by anomalous speech than coherent speech would be evidence supporting both the syntactic and semantic account. If the processing system makes attempts at processing syntactically and semantically anomalous speech, it should bring about interference in semantic and syntactic processing during reading.
As regards the nature of the effect of anomalous background speech in reading, the data of Experiment 2 and 3 can be accommodated either by the syntactic or the semantic account, as long as the emphasis is on shared processing and not on shared representations between the two information sources. This is because Experiment 2 obtained no evidence for the view that similarity in general semantic content between the two sources of information would exacerbate the disruption effect in reading. However, on the basis of Experiment 2 and 3 it is not possible to tease apart the relative contribution of the semantic and syntactic component, as the scrambled speech used was anomalous both syntactically and semantically. The random word salad did not conform to the syntactic rules of the language, neither did it express any sensible meanings, but rather strange combinations of words that may sometimes appear humorous. Experiment 4 was designed to help tease apart the effect of the two types of anomaly. This was done by testing disruption effects in reading for two types of scrambled speech: one that is both syntactically and semantically anomalous (similarly to Experiment 2 and 3) and another that is semantically anomalous but syntactically correct. The latter condition was created by first randomizing the order of words of a coherent text and then editing the word list in order to construct syntactically correct but semantically anomalous sentences. If syntactic anomaly is particularly disruptive, we should then find more robust interference effects for scrambled speech that is both syntactically and semantically anomalous than for scrambled speech that is only semantically anomalous.
The present study was conducted to examine disruption effects in reading long, syntactically complex sentences due to different types of background speech played while participants were engaged in reading expository texts. Readers were asked to ignore the background speech and concentrate only on reading. Effects of background speech were investigated by registering readers’ eye movement patterns for a selected set of sentences embedded in relatively long texts. The target sentences were center-embedded relative clause sentences. For a half of the target sentences, syntactic complexity was further increased by changing in the main clause the word order from the default order (SVO) to a marked and more infrequent order (OSV or OVS).