What is interaction

This is the first homework for the PCom, which is quite… philosophy rather than a project-based question. But as is known to all, it will be better to take serious consideration in methodology part before starting the practical part (and also a good transition from vacation to semester).

In the article I will first answer the questions proposed by our course, and then trying to say something except the questions but which I want to talk.

Since I’m not a native-English speaker, if there is some improper statement, please let me know.

How would you define physical interaction?

This item is composed by two words, physical and interaction. So one of the good methods is, first analysis the two words separately, then to figure out how to combine them together.


Physical here shouldn’t means the opposites parts of the Mental, and should be more close to the meaning of the “real part of the world”, means visible, audible, and most important part, tangible things in order to make a difference with “Screen based Interaction”.

Moreover, if we take consideration of the interaction here, physical should not only means “happen in the physical world”, but also “computing in the physical world”. Just as the course name “physical computing”, the physical here should include the meaning together with computing, that is to say:

Physical computing, in the broadest sense, means building interactive physical systems by the use of software and hardware that can sense and respond to the analog world. While this definition is broad enough to encompass things such as smart automotive traffic control systems or factory automation processes, it is not commonly used to describe them. In the broad sense, physical computing is a creative framework for understanding human beings’ relationship to the digital world. In practical use, the term most often describes handmade art, design or DIY hobby projects that use sensors and microcontrollers to translate analog input to a software system, and/or control electro-mechanical devices such as motors, servos, lighting or other hardware. 


As is known to all, the contents from WikiPedia is not always correct, but here some important points are included, those are:

  • interactive physical systems
  • software and hardware — sense and respond to the analog world
  • understanding human beings’ relationship to the digital world

Though the third item is not so academic, but that’s the item I like most, that is to say, the whole structure should be served onto human beings, but not only the cold machine which could make profits but no emotional part related to anything into people.


For the Interaction part, I totally agree the definition proposed by Crawford, which contains three cores of the whole system, they are:

  • Listening (Input)
  • Thinking (Process)
  • Speaking (Output)

And I also agree with the point proposed by him, which is to say, in an interaction system, the most important thing is not the visual/sound/effects, the selling point should be the whole interaction process, and the experience which user will get during the communication with the system.


So if we combine those two parts together, we can get a version 1 definition of Physical Interaction, that is:

Physical Interaction is a kind of interaction systems based on physical computing, differentiate with the Interaction happened beneath a screen, totally human-based interaction or other kind of interaction. Typically the system will have many sensors to listen, or to sense user’s behavior, processing the datas with premade program, and speak, or reacting to the user in the real world. The aim of physical interaction is always for exploring human beings’ relationship to the digital world, but not only for producing or profits.

What makes for good physical interaction?

First thing is the interaction-level, which is proposed by Crawford but only with a vague definition. Personally I would say we need to make it with more details and clearly. Since I’m the person more like a “boring” User Interface Technologist rather than an “interesting” Interactive designer (By Crawford’s words), I would analysis such a vague definition in technology aspects.

Proper Sensing and Actuating

For physical interaction, the input part invade into the physical world, that is, jump out of the boundary of the traditional devices like mouse and keyboard, but with many fancy sensors like kinect, microphone arrays, wearable sensors and so on.

But good projects are not the gathering of advanced sensors, and advanced sensors shouldn’t be the most important part of the interaction. In fact, all sensors should serve for the functions and needs — if we want to trace people’s motions, one kinect is better than an array of GoPro; if we only need to get a face shape, a camera with standard 50mm lens will be better than a depth camera which will generate more useless information which might interface the process speed.

The same story happened in the Actuating part. Since most of the physical interaction projects will choose to use physical actuating as their output, it is important to choose a proper actuating, like shape change, moving, make sound, or beat the user up by a machine arm. Things should be simple, clearly and rational in the speaking part, even if you want to make a surprise for the users, you should keep the principles above.

Proper Response time

Though whole engineering world is chasing for a “Faster, Higher, Stronger” system, this might not be so proper for a physical interaction system. Too faster is as bad as too slow, a proper, accepted response time is needed for a good system.

But it is not easy to define a “proper” time for all the projects, the proper here should based on each project one by one. For instance, if we use a system for information collection, like refer the weather, it is good for us to get the weather information once we make an enquiry since we do not want to wait. But if the system is so smart, that when you type “we”, or even you haven’t sent an enquiry, the information comes to your side, you may feel uncomfortable.

For the physical interaction, things will be more complicated. Things happened in the physical world is much more real than a virtual image through a screen, a proper, not scaring and comfortable response time is required. Typically the reaction time always be too long, like you wave your hands, after 1 second the machine will then react that gesture — But things are not so absolutely, a proper response time should be kept.

Are there works from others that you would say are good examples of digital technology that are not interactive?

I want to introduce the following useless machine below:

Of course, this is a totally useless, but interesting interactive machine, the machine can listen to whether someone change the switch, and speak “shut down”, to change the switch back to its initial states.

After that, people make a joint between two machines, make conflict between each other, things like the belows:

This is interesting, but not a interactive device, since people can only watch, laugh, but noting to do with input and output.