User Experience Design: Test user psychological load with mobile Input method

Article Description: A new perspective of User experience assessment--the measurement of user's psychological load.

User experience is determined by many factors, but for different types of products (including different user groups, usage purposes, usage scenarios, etc.), the weights between the dimensions and the dimensions are not the same.

Take the mobile input method as an example, this is a typical tool class product. The performance of user input (including speed and accuracy) is the most important factor to determine the overall user experience level, so it is also the most important research focus in the experience evaluation. However, in practice, we often find that the input of poor performance is usually the user's subjective satisfaction is low-this is easy to understand, there is no problem, and some of the input performance of the experimental programs are often unable to get the highest degree of subjective satisfaction rating users. For example, for the key size of the program, because users need to be very cautious input, the correct rate of input is higher, but will feel nervous, not easy, resulting in poor subjective satisfaction.

Psychological load and subjective satisfaction of product

In fact, the user's psychological load level in the use of products also directly affect the user's subjective satisfaction. The definition of mental load (Mental workload) is diverse, and we have no intention of exploring its precise meaning here. In general, we can think of mental load as a corresponding concept of physical load--the physical energy required to complete an operation--the thought and psychological stress that is required to carry out an operation or accomplish a task.

In psychology, the Yerkes-dodson Law describes the inverted U-shaped relationship between the level of psychological arousal (arousal) and operational performance (performance). and the psychological load and arousal level are positively correlated. In other words, under both low and high mental load levels, the performance of the operation will be negatively affected. In sports competitions, if the athlete is absent-minded, slumber (at low psychological load level) or opposite, extreme tension (at high psychological load level), play will be adversely affected, that is the truth.

Measurement of mental load

After understanding the influence of psychological load on subjective satisfaction and operation performance, how to measure mental load is a problem that must be solved. At present, there are two main types of psychological load measurement in academia:

Physiological index measurement method. The psychological load level was measured by measuring blood pressure, heart rate, skin conductivity, brain wave and other physiological indexes. There is a big problem with this method. First, the psychological load changes can be reflected in the physiological indicators, but the mechanism is very complex, and the changes in physiological indicators are not entirely caused by psychological factors. Therefore, the method of monitoring physiological index response psychological load level is questionable. In addition, this method is not feasible in the enterprise-level user research work.

Self-reporting evaluation method. The main is to let the participants fill in the psychological scale to measure the mental load level. We are currently using the software version of the NASA-TLX scale developed by NASA to measure the psychological load level of a user completing a test task. NASA-TLX Scale is one of the most widely used and effective psychological load scale, and its simple structure is very suitable for the daily user research work.

Six dimensions of the NASA-TLX scale:

Psychological needs (Mental Demand): The amount of mental effort expended to accomplish a task

Physical needs (physical Demand): The amount of physical energy expended to accomplish a task

Time required (temporal Demand): The length of time required to complete a task

Performance (performance): Effect of task completion

Degree of effort (effort): the level of effort required to complete a task

Frustration (frustration): a sense of frustration after completing a task

The participants were required to rate their behavior on these six dimensions. The rationale is the same as the common Richter scale, which is not to be summarized here.

After scoring, the weights of each dimension need to be set. The basic principle is to order the importance of six dimensions, according to different sorts of different dimensions of the weights, so as to calculate the final psychological load index.

For the mobile Input method product, the input performance and the psychological load level directly affect the overall user experience. Therefore, high input performance and low mental load design will be the direction of experience upgrade.

Tips:

Because the NASA-TLX scale needs to be filled out by the user itself, the interpretation of the meaning of each dimension becomes particularly important. We have to make sure that the understanding of different users is broadly consistent.

One of the problems with the use of NASA-TLX in Western countries is that western users tend to exaggerate their subjective feelings. A recurring phenomenon is that in the multiple-program alignment, the user has a high level of psychological load on the easier task, so that there is no room for elevation when they find more difficult tasks. And for Chinese users, many people are not good at perceiving their true feelings. You will find that no matter how difficult the task is, the user's score is always small and almost in the middle. In the face of such users, it is necessary to conduct a mock demo before the formal test, so as to adapt them to the way they perceive themselves.

The use of NASA-TLX scale, as well as all subjective measurement of a taboo is to the measurement of the results of the comparison between individuals. Because the subjective feelings between different people are not comparable. It's like two people say they have pain, but we can't use the same criteria to determine who is more painful than who. Therefore, the psychological load index is best for the same group to evaluate the different programs.

Objectively speaking, the introduction of user psychological load can not completely solve the experience assessment problems encountered, and does not apply to all products, but at least let us to the "real user" a step closer.