Social and Cognitive Prostheses

Person with calculator watch on wrist
Photo by Andrik Langfield on Unsplash


Value in software can be assessed by it’s monetary worth, perceived importance or merit to someone. The primary way this value is derived from software is for it’s ability to help someone solve a problem, complete a task, achieve a goal or otherwise be more productive (Page, Johnston and Rollison, 2009). In this way, the software acts as a prosthesis.

Imagine that you had lost a leg. To help you walk, you would rely on a prosthesis—the modern-day steel-and-plastic equivalent of a wooden leg. This prosthesis makes up for a lack, allowing you to accomplish a task (in this case, walking). Not only do people rely on physical prostheses, but they also can rely on cognitive ones. For instance, an electronic calculator is a cognitive prosthesis, filling in for a lack so that you can accomplish a specific task (Kosslyn and Miller, 2014)

Likewise little or no value may mean it doesn’t help someone solve a problem, complete a task or achieve an goal, or causes further hindrance or damage. For example, a prosthetic leg could be too heavy or not articulated enough to be of value. It may even cause harm through injuries. A calculator application may give incorrect results or be too difficult to use causing an accountant to lose an important customer. Value isn’t just for customers and end users, but also project value to business stakeholders.

Value also exists in time and contexts which are subject to change. A prosthetic leg doesn’t deliver any value whilst it’s not being used. It may not deliver any value when it’s being used for a task other than walking. A messaging application loses all its value when everyone is gathered together in person, but becomes a lot more useful when everyone is remotely communicating. In agile development and testing, these are important considerations and discussions that form stories and claims of value.

It’s also important to note that software only helps (or hinders) and isn’t completing the task itself. A prosthetic leg won’t replace the entire action of walking and a software program won’t replace a human being in solving a human problem.

What, say, a pocket calculator does shows that it does something different to a human calculator — for example, when approximation is called for; second, humans make up for what the calculator fails to accomplish, often without noticing that they are doing it — the computer is a social prosthesis (Collins, n.d.)

Customers, end-users and business stakeholders are three classes of people who value software or are affected by it, but there are others too. For example:

  • Professional reviewers and press matter, because reviews or news reports could make or break sales of the software or the reputation of the organisation creating it.
  • Governments matter, because they have the power to fine and prosecute where software or companies have broken laws.
  • Society-at-large matters too. A problem in the software of a nuclear power plant could cause a melt-down that brings loss or harm to the power plant owners, workers and software vendor, but the impact to other people goes far beyond that! No-one wants harm to come to people in that way, so everyone matters when it comes to nuclear safety, not least because it would lead to litigation against the company too.


Social and Cognitive Tools

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Another way to think about the value of software is as a social or cognitive tool. Software is an extension of the human mind in the same way that a spanner or whisk is an extension of the human hand. Each tools is specially designed for a purpose where it can deliver value, whether the tightening bolts, scrambling eggs, communication or data processing. Application (often shortened to “app”) is another popular way to think about software as something that’s applied to solve a particular problem, task or completion of a goal, and is therefore congruent with the idea of a social or cognitive tool.



The capability of software to fulfil a purpose or objective isn’t the only way value can be delivered or threatened. What makes a sports car better than a regular car or a restaurant meal worth paying extra money for in comparison to home cooking? Both cars can fulfil the purpose or objective of getting from A to B and both meals will fulfil their purpose of supplying energy and nutrition to someone. It’s the same with software, what makes a software product worth paying for when the same task can be achieved without software, such as pen-and-paper over a calculator? Likewise, what makes one product better than another when they both can be used to help complete the same task, such as a calculator vs spreadsheets or Microsoft Excel vs OpenOffice Calc?

In software, this capability to help complete a task is built upon functionality which is, from the user perspective, end-to-end operations with a single user input and output. Achieving capability value involves the execution of one or more user functions to help complete a task, achieve a goal or solve a problem. However there are different dimensions to quality that can still affect value in other ways known as parafunctional (or non-functional) quality dimensions (Kaner, 2010).

Even though digital computers have the same capabilities, even though they can do nothing beyond the primitive computing machine devised by Alan Turing, the speed of the processor of course ultimately affects the overall usefulness of a computer system. Any computer that’s slower than the human brain in performing a set of calculations is useless (Petzold, 2000)

Performance is an important parafunctional quality dimension. A software product, system or service may do the job, but if it does it too slowly to be useful, or does it slower than another rival product, its value to someone is going to be low. However performance quality can’t exist without capability quality (functionality). Performing a task quickly or slowly can’t happen unless it’s first possible to complete the task.

Click here to see a full list of quality dimensions.



Value in software is primarily derived from its ability to help solve a problem, complete a task or achieve a goal. In this way, software can be thought of as a social or cognitive prosthesis or tool, or simply an application – something to be applied to solve a particular problem. Value can be captured as user stories that can be tested at expanded upon. Note that capability to complete a task, solve a problem or achieve a goal for someone isn’t the only way in which value is achieved or threatened, and testers must consider many other parafunctional dimensions to value and quality.



  • Agile Alliance, User Story Template. [online] Glossary. Available at: Link
  • Beck, K., 1999.  Extreme Programming Explained: Embrace Change. 1st ed. Boston: Addison-Wesley
  • Cohn, M., 2008. Advantages of the “As a user, I want” user story template. [online] Mountain Goat Software. Available at: Link, see also: Link
  • Collins, H., n.d. Key Concepts [online] Harry Collins. Available at: Link
  • Davis, R., 2001. XP2001 Conference (see Agile Alliance reference)
  • Kaner, C., 2010. BBST Foundations 1B: Overview and Basic Definitions in Software Testing. [online] TestingEducation. Available at Link (t.i. 8m34s)
  • Kosslyn, S. and Miller, G.W., 2014. Social Prosthetic Systems. [online] Psychology Today. Available at: Link
  • North, D., 2007. What’s in a Story? [online] Dan North & Associates Ltd. Available at: Link
  • Page, A., Johnston, K. and Rollison, B., 2009. How We Test Software at Microsoft. 1st ed. Redmond, WA: Microsoft, p. 297
  • Petzold, C., 2000. Code: The Hidden Language of Computer Hardware and Software. 1st ed. Redmond, WA: Microsoft Press, p.259.

2021-10-16: Updated

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