The purpose of this study was to examine the bidirectional effects of simulated driving and conversations using different speaking modalities. Participants included 30 males and 30 females with no history of speech, language or hearing disorders. The participants were divided into three age groups: 20s, 40s, and 60s. They completed a driving simulation task in isolation and also while speaking on a hand-held or hands-free cell phone or with a passenger in the car. Speech measures included speaking time ratio, mean, and standard deviation of intensity, as well as mean and standard deviation of fundamental frequency in semitones. Driving measures included standard deviation of lane position, mean, and standard deviation of speed, standard deviation of steering wheel position, and the average number of steering wheel turns. There were significant effects of speaking while driving on mean intensity, speaking time ratio, standard deviation of steering wheel position, and the number of steering wheel turns. There were significant gender effects for speaking time ratio, standard deviation of intensity, and mean intensity, with the females having higher speaking time ratios, and the males having a higher standard deviation and mean of intensity. There was a significant age effect for mean fundamental frequency, standard deviation of lane position, and the standard deviation of steering wheel position. For mean fundamental frequency, the 60s group were lower than the 20s group. The 60s group had a higher standard deviation of lane position and standard deviation of steering wheel position. These findings reveal effects on both speaking and driving performance when speaking and driving concurrently. This has potential clinical implications for planning therapy activities that will help individuals generalize their learned skills from quiet, distraction-free clinic rooms to more realistic situations with distractions and background noise.

This study examined interference between three non-speech tasks and concurrent speech performance. The non-speech activity consisted of computer-based mathematical, language, and visuospatial tasks. The speech tasks included a procedural discourse monologue and a conversation. Participants included 60 adults in two age groups with 30 participants each. The younger adults were aged from 18 to 30 years and older adults from 55 to 82 years. Each participant completed the non-speech tasks in isolation, the speech tasks in isolation, and then each of the speech tasks concurrently with each of the three non-speech tasks. Speech acoustic measures included the mean and standard deviation of intensity and fundamental frequency as indicators of prosody, speaking time ratio to reflect speaking versus pausing time, and speech rate. Non-speech measures included total responses, correct responses, and accuracy. Statistical analysis revealed significant divided attention effects on speech, with increases in fundamental frequency and decreases in speaking time ratio, speech rate, and intensity. Performance on all non-speech tasks was negatively impacted by speech, as there was a significant decrease in total responses and total correct responses overall. There was a significant age effect for intensity and fundamental frequency variability, in that the younger group had less prosodic variation compared to the older group. The present findings provide some evidence that the effects of divided attention increase with age, as older adults gave fewer responses than younger adults overall. However, results indicate older adults prioritize accuracy over speed compared to younger adults. These findings suggest that bidirectional interference occurs between speech and mathematical, language, and visuospatial tasks. The results expand what is known about bidirectional interference between speech and other concurrent tasks, as well as the effects of age on divided attention.

The purpose of this study was to examine interference between concurrently performed speaking and driving tasks. Participants included 60 adults, 30 males and 30 females, with no history of communication disorders. They were divided into three different age groups of 20 participants each: younger (20s), middle-aged (40s), and older (60s). The participants were given a list of topics to consider and were instructed to select eight topics that they could talk about; they completed five practice trials of the driving simulator prior to the experimental recording to eliminate practice effects. Each participant completed the speaking task and driving task both separately and concurrently. The speaking task consisted of producing a monologue about the topics that they had selected. Dependent measures for speech included metrics relating to intensity, fundamental frequency, and the ratio of speaking to pausing time. The simulated driving task involved maintaining a constant speed and lane position on a freeway. Dependent measures for driving included metrics relating to speed, lane position, steering wheel position, and a count of steering wheel turns. Results indicated significant divided attention effects in speaking time ratio, intensity, speed, and steering wheel control. There was a significant age effect for intensity and fundamental frequency as the younger group had less variation with these variables compared to the other age groups. There was a significant age effect for lane position, steering wheel position, and speed as the younger group had less variation in lane and position compared to the other groups and the older group had more variation in speed and steering wheel position compared to the other groups. There was a significant gender effect for intensity and lane position as the females had less variation in intensity and more variation in lane position compared to the males. These findings suggest that divided attention conditions impact both speech and driving performance. The results also shed some light on the effects of age on concurrently performed speech and driving tasks. These findings imply that divided attention conditions should be incorporated in treatment to help patients generalize the skills learned in therapy to everyday communication.

The present study examined the divided attention effects of three non-speech tasks on concurrent speech motor performance. These tasks targeted linguistic, cognitive, and manual motor activity. Participants included 60 healthy adults separated into three different age groups of twenty participants each: college-age (20s), middle-aged (40s), and older adults (60s). Each participant completed a speech task once in isolation and once concurrently with each of the three non-speech tasks: a semantic decision task, a quantitative comparison task, and a manual motor task. The non-speech tasks were also performed in isolation. The speech task involved repeating a target phrase each time a beep sounded, for a total of fourteen repetitions. Dependent measures for speech were derived from lip kinematic recordings from a head-mounted strain gauge system. Dependent measures for the other tasks included timed response counts and accuracy rates. Results indicated significant divided attention effects, impacting speech and nonspeech measures in the linguistic and cognitive conditions, and impacting speech measures in the manual motor condition. A significant age effect for utterance duration was also found, as well as a divided attention interaction with age for cognitive task accuracy. The results add to what is known about bidirectional interference between speech and other concurrent tasks, as well as age effects on speech motor control.