Effects of conversational noise, locus of control, and field dependence/independence on the performance of academic tasks

The effect of speech and speech intelligibility on task performance

The aim of this study was to find out what are the effects of three different sound environments on performance of cognitive tasks of varying complexity. These three sound environments were 'speech', 'masked speech' and 'continuous noise'. They corresponded to poor, acceptable and perfect acoustical privacy in an open-plan office, respectively. The speech transmission indices were 0.00, 0.30 and 0.80, respectively. Sounds environments were presented at 48 dBA. The laboratory experiment on 36 subjects lasted for 4 h for each subject. Proofreading performance deteriorated in the 'speech' (p < 0.05) compared to the other two sound environments. Reading comprehension and computer-based tasks (simple and complex reaction time, subtraction, proposition, Stroop and vigilance) remained unaffected. Subjects assessed the 'speech' as the most disturbing, most disadvantageous and least pleasant environment (p < 0.01). 'Continuous noise' annoyed the least. Subjective arousal was highest in 'masked speech' and lowest in 'continuous noise' (p < 0.05). Performance in real open-plan offices could be improved by reducing speech intelligibility, e.g. by attenuating speech level and using an appropriate masking environment.

A model predicting the effect of speech of varying intelligibility on work performance

Speech is the most distracting sound in (open-plan) offices. Several laboratory studies have shown that speech impairs the performance of, for example, reading and short-term memory. It is not the sound level of speech that determines its distracting power but its intelligibility, which can be physically determined by measuring the Speech Transmission Index (STI). The aim of this study was to develop a mathematical model that predicts how much the performance is reduced due to speech of varying intelligibility. The model was based on the literature according to which performance decrements have been 4-45% depending on the task. The best performance occurs when speech is absent (STI=0.0), and the strongest performance decrement occurs when speech is perfectly heard (STI=1.0). The shape of the performance vs. STI between 0.0 and 1.0 was adopted from the general speech intelligibility theory. The performance starts to decrease when STI exceeds 0.2. Highest performance decrease is reached already when STI exceeds 0.60.

PRACTICAL IMPLICATIONS

The prediction model can be exploited in the evaluation of work performance in different acoustical conditions in open-plan offices when STI is known. It can be utilized to promote actions aiming at better acoustical conditions.

Taking charge of remembering: locus of control and older adults' memory for speech

The relation between control beliefs and recall of spoken word lists and prose passages was assessed for 32 older adults, ages 62 to 85, in a task where they were given control over presentation of stimuli. They differed in the degree to which they believed that factors within their control (internals) or outside their control (externals) affected their intellectual functioning; they were similar in age, education, vocabulary, and digit span. They were required to stop the speech input at points of their own choosing to recall the stimuli on a segment-by-segment basis. Externals were more likely than internals to make inaccurate predictions of the number of words they could remember and to choose longer segments than they could recall. Results suggest that externals are poorer than internals in monitoring on-line memory processing.

Locus of control differences in memory recall strategies when confronted with noise

In some individuals, noise appears to have an adverse effect on memory recall. This decrement may result from a shift in the memory strategy being employed. Studies have shown memory strategies used by persons with an internal locus of control differ from those used by persons with an external locus of control. The present investigation asked subjects who were classified as either internal or external in locus of control to recall words presented under conditions of noise and of quiet. Word recall was aided by providing subjects with potential memory strategies. Each word list included words from meaningful content categories (which favor a semantic strategy) and word pairs that rhymed (which favor a perceptual strategy). Though internal and external subjects did not differ in total words recalled, they did differ in their use of strategies. Whereas internal subjects' strategies were unaffected by noise, external subjects decreased their use of the higher level semantic memory strategy (content categories) and increased their use of lower level perpetual (rhymes) strategy in the noise condition. The results are discussed in terms of a differential arousal hypothesis.