Ergonomics of Interaction

Introduction

Ergonomics, also known as human factors, is the study of the physical characteristics of human interaction with other systems. Ergonomics helps the designer to design an interface that enhances user performance. It is a vast field of human psychology but also closely related to HCI. For this reason, we are going to study some important factors of ergonomics as a part of this introductory course.

Arrangement of controls and displays

To enhance performance, display sections and controls should be grouped logically. A logical arrangement will allow the user to access them rapidly. The logic of arrangement depends on the application and the domain. Some possible arrangements are:

• Sequential: The controls and displays that form a sequence of actions to perform a task are organized in their order of use.
  Example: There are two Educative signup forms below. The one on the left is the actual form. As you can see, it has all the information and action fields in sequential order of how they should be filled out. The one on the right has been edited. Only the sequence of information has been changed. This form distracts the user’s attention all over rather than gaining the user’s focus on one piece of information at a time. Due to this reason, this form has a high probability of producing user errors and mistakes.

• Frequency: The controls and displays are arranged based on how frequently they are used. The most frequently used control will be placed in the most easily accessible location.
  Example: Let’s compare the placement of two different options of a text editor. One is the “new file” option that creates a new file, and the other is the “dictionary” option that has suboptions of different dictionaries to select from. The former action is a more frequently used one compared to the latter one. Observe their placement in the images down below. The new file option is more accessible than the dictionary option.

In addition to the arrangement of controls and groups, here are some points to consider regarding the interface as a whole:

• Critical displays should be placed at eye level.
• All necessary displays and controls should be accessible to the user without extra body movements.
• Controls should be spaced apart enough to avoid slips like selecting the wrong control.
• Lighting inside the room should be arranged to avoid displays with distorted reflections.

Use of colors

The use of proper colors is one of the most important ergonomic concerns. As we have already studied, humans have limitations on visual perception, and illusions can disrupt the interaction by causing confusion. Also, we know that a significant number of people have color vision deficiency. Here are some important rules regarding the use of color that shouldn’t be violated without any good reason.

• The colors used should be distinct.
• The distinction of colors should remain unaffected by changing contrast.
• Refer to common conventions of colors when selecting them. For example:
  • Red: Usually associated with a stop or a warning. In an interface, use red for alarming and emergency situations.
  • Green: Usually associated with go or all good. In an interface, green should be used for indicating normal activity or success.
  • Blue: Usually considered a calm color. In an interface, blue should not be preferred for indicating critical controls.

Example: Here is an example of an online wholesale meat supplier’s shop. They have used bright red as a background color for their website with white as the font color. This is a color combination that should never be used.

Physical environment

Two important points that we need to consider when designing an interface are:

• The place where the system will be used.
• The intended users of the system.

For example, some considerations to take into account are:

• The controls on the interface should be accessible by users of all sizes, from the smallest person or a person in a wheelchair to the tallest person.
• Whether the system will be used in a public environment or personal space. The level of distraction in a public environment is usually greater than in a personal environment. If intended for a public environment, the system should aim to engage the user more by providing continuous feedback on the task.
• Whether the system will require users to sit or stand. In the case of personal computers, users may be required to sit for a long time, so the seating place should be comfortable.

Health issues

Users’ health and safety concerns are another factor that can affect the design of an interface. Apart from the hazardous results of a poorly designed safety-critical system, below are some health factors that directly influence interaction quality and user performance. Please note that all these factors are part of the physical environment that concerns human health and safety.

• Physical position: Interactions shouldn’t be exhausting and tiring for the user. All the displays and controls should be easily accessible by the user. Also, interactions should not require the user to sit or stand for long periods of time.

• Temperature: Extreme hot or extreme cold temperature can decrease user performance and in some cases, can affect health as well.

• Lighting: The work environment should provide adequate light to avoid user’s discomfort or eye strain while looking at the screen.

• Time: The required time of interaction should be limited and controlled. Excessive exposure to displays can be harmful to users.

• Noise: Noise levels should be maintained and controlled at an appropriate level. Extreme levels of noise can cause pain to the human ear, disturbance, and even hearing loss in an acute case.