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#20 - What is Doherty's Threshold?

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Article written by
Juan Jesús Millo

Where does the Doherty Threshold come from?

Who is Walter J. Doherty and what can he tell us about reaction time? How long are we willing to wait for a system to react?

Surely, sometime, in a conversation with another person, we remain silent because we do not remember what we wanted to say, breaking the flow of the conversation; the moment we finally remember what we wanted to say, it is difficult to start again, since we have to make a cognitive over-exertion to remember the narrative of it.

Productivity based on Doherty threshold

Now we are going to transfer this to computer systems; Richard P. Kelisky and Doherty, in 1976, did a study at IBM to check the degradation of our attention with respect to the response time of a system. You may have all played the Sims, where you tell the character what to do and in what sequence of commands, but you have a cap on actions, right? Well, this is not a joke, since humans outside that screen work in the same way; when we think about doing something it is not a single action, it is a chain of actions, which we keep in our short-term memory, as if it were RAM memory, but what if this sequence was affected by external agents? In our real world it would be a phone call, or in our digital world, that our computer is not powerful enough to execute all actions in real time.

If this is affected, what is achieved is an alteration of the thinking process, giving place to having to think again this chain of actions, resulting in a longer processing time and lowering our productivity. Then the time of reaction that is looked in a system so that we have a fluid experience between action:reaction or TER (time of response of the system) are 400 milliseconds, this is what is known as the Doherty's Threshold.

If the system achieves this time, we will be at 100% of our productive capacities, while if it is higher, our attention will go to the trash and we will have problems to focus again in this sequence, causing an unnecessary frustration.

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