The human working memory and the implications on Apple CarPlay
By: Mackenzie Legg
Tags: Usability, Design, Apple, UX, Ts

Today there are more things fighting for our attention than ever before. We are constantly juggling work, family, and social lives. What we don’t realize is, try as we might to multitask, our attention span is quite limited. Recent findings suggest that we can hold about four items (plus or minus 1) in our short-term memory at the same time (Johnson 110). This means that we only have the capacity to focus on a few items at any given moment. Difficulties may arise when doing something that engages other parts of the brain such as driving a car. In our busy lives, with our email, phone, and navigation at our fingertips, using a mobile device while driving is common. A recent study for the European Commission “estimated that driver distraction is likely to be a factor in 10–30% of all road collisions in Europe each year” (IAM Roadsmart ii). In the past 10 years, hands-free phone laws have been established across the U.S. and car manufacturers have responded by making hands-free calling standard in most in-car “infotainment systems”.

In 2014, Apple launched Carplay, a seamless way to integrate your iPhone to your car’s infotainment system. The system not only included hands-free calling, but also voice control for other functions like music selection and navigation via Siri (Apple, Inc.). Studies have shown that human working memory is limited and it has been proven that using a mobile device while driving increases cognitive demand. With this implication in mind, and further development of voice control functions, Apple Carplay is on track to help drivers safely interact while driving.

Defining Working Memory

Two separate types of memory — long and short term — have been defined as early as 1883 by Francis Galton. In 2012, Alan Baddeley published his comprehensive findings on working memory as a way to more accurately portray what goes on in short-term memory. He postulated that short-term memory was the “simple storage of information” while working memory (WM) “implies a combination of storage and manipulation” (Baddeley 5). Baddeley proposed a system for working memory that consisted of four parts: the Central Executive, the Visio-spatial Sketchpad, the Phonological Loop and the Episodic Buffer. The Central Executive is the central controller. The Visio-sketch Pad was distinguished as a short-term visual information store where there was very little capacity. The Phonological Loop thought of as the store for verbal information. The Episodic Buffer being the link across all sections of WM. The Central Executive is the portion in charge of attention. He theorized that the prefrontal cortex is where the working memory functions (Baddeley 3).

Defining Cognitive Load

When discussing the limits of working memory and driving, one must consider what causes distraction. A combination of visual, manual, and cognitive components make up a distraction. Driving can be done safely when the task has the full attention of the working memory. Distracted driving is when the attention of the driver is diverted from the functions that constitute safe and effective driving towards a competing stimulus. This may result in a lack of attention to tasks critical for safe driving. For example, while driving a car, you have to monitor the road, read road signs (visual), and steer the wheel (manual). If the cognitive component, usually regarded as a “general withdrawal of attention”, or a wandering mind comes into play, the driver has become distracted. Often used interchangeably with cognitive distraction, cognitive load is defined as the amount of energy being demanded by an alternative task. The concept of cognitive load. factors heavily in studies conducted on the implications of working memory and driving (Reimer et al. 454–468).

Multitasking and the Bottleneck Effect

Meyer and Kieras (1997) completed research on executive cognitive processes and multiple-task performance. Based upon their work, they theorized that when presented with multiple tasks, the brain cannot fully focus. If multiple tasks are performed, the tasks are prone to error and take longer to complete, perhaps even doubling the time they take to complete (Meyer and Kieras 63–87). Their basis for this is that the brain must restart and refocus on each task and the time in the middle of the swap between tasks leaves gaps inefficiency. So, not only does one do each task less effectively but they lose time in the process.

A study completed by Ruthruff (2001) focused on a bottleneck effect that happens when people try to carry out two separate response tasks simultaneously. Similar to the findings by Meyer and Kieras, Ruthruff found that responses were delayed for one or both tasks. Additionally, he noted that the second task is often slower at first, then speeds up when the stimulus is reduced. The finding is known as the “psychological refractory period (PRP) effect” (Ruthruff 73).

Working Memory and Driving

What do the limits of the working memory mean for drivers? Research completed in 2012 for MIT, showed that as the cognitive demand on the driver increases, the awareness of their environment decreases. The study used recordings of the drivers’ gaze and driving performance from 108 drivers of equal genders across three age groups, 20–29, 40–49 and 60–69, recruited in the Boston, MA area. (Reimer et al. 454).

A mid-size sport car (Volvo XC90) was instrumented with sensors including cameras for capturing driver behavior, vehicle surroundings and audio recording. An eye-tracking system was also set up. The Experiment was conducted on a major highway where the speed limit was 65mph. The drivers were presented with low, moderate and high levels of cognitive workload. For the low level, the driver was given a set of numbers and was asked to repeat those numbers back out loud. At mid-level, the driver was asked to hold each number in memory and asked to speak out loud the previously given number. At the high level, the driver was asked to report verbally, the sum of the numbers given. Driving speed, steering wheel position and acceleration data were recorded directly from the car’s built-in sensors or CAN (Controller area network). The driver’s visual attention was determined by eye-tracking x and y coordinates of the eye position on a vertical plane and a distance as wide as the windshield. Gaze concentration was determined by watching the deviation from standard gaze coordinates. The study found that horizontal gaze concentration was prominent with increased cognitive demand. Meaning, there was a lack of dispersed gaze. “67% of the drivers narrowed the distribution of their eye fixations during the highest-demand period relative to the single-task driving period” (Reimer et al. 465). Researchers studied “gaze concentration” of drivers and found that their awareness of surroundings were affected by increases in cognitive demand. They concluded that developers of advanced driver support systems should consider gaze concentration as a measure of driver cognitive workload because gaze measurements detect visual demand (454).

Apple Carplay and Cognitive Performance Study

IAM Roadsmart, the UK’s largest independent road safety charity, released a report in January 2020 where gaze concentration was one of the criteria used for examining driver safety. This study provides more recent insight on the effect Apple Carplay has on the cognitive performance of drivers. The study used a driving simulator equipped to measure the driver’s “reaction time, eye gaze behavior and vehicle control” (IAM Roadsmart 3). Participants drove the vehicle through 3 trials, one “control drive” where they did not interact with the infotainment system, one “voice-enabled drive” where they performed tasks using only the voice-activated features, and one “touch-enabled drive” where they performed tasks using the touch screen. While driving they were asked to complete five system tasks, using either voice function or touch, including:

Playing music on Spotify

Playing BBC radio

Navigating

Receiving text messages

Making a call

While they completed these tasks, they were tested on their reaction time by responding to red bars displayed on the screen. “The main purpose of the red bar was to measure reaction time to an external stimulus whilst interacting with the infotainment system” (IAM Roadsmart 43).