SUS: A System Unusable for Twenty Percent of the Population
Summary
Did you know that the SUS creates biases in your research, affecting one in five people? That’s right! People with disabilities, especially those who use assistive technology, are not considered by most of the questions in the SUS. As a designer for the public sector, this could lead to you making design decisions that don’t take into account 20 percent of the visitors to your website.
Key Insights
-
•
Screen readers allow users to navigate web pages quickly by jumping through well-structured headings and content.
-
•
Low vision users often rely on system-wide screen magnification and color inversion settings to reduce eye strain.
-
•
Alternative navigation methods like head mice and voice dictation are selected based on task and user condition, not used exclusively.
-
•
Traditional lab-based usability research often prioritizes convenience over real assistive technology configurations, leading to inaccurate results.
-
•
Assistive technology users rarely use default settings; they extensively customize tools over time for optimal use.
-
•
The System Usability Scale (SUS) includes questions that confuse assistive technology users and do not capture their true experience.
-
•
Fable’s Accessible Usability Scale adapts SUS questions to better reflect the experience of assistive technology users.
-
•
Initial data shows screen reader users report significantly lower usability scores (mid-50s) compared to screen magnification users (low 60s).
-
•
Users’ lowered expectations after years of experience may mask the true severity of usability issues in assistive technology contexts.
-
•
Measuring accessibility usability accurately enables benchmarking and progress in improving digital products for all users.
Notable Quotes
"I’ve been using screen readers for 30 years and accessibility has always been a passion of mine."
"Screen readers let us jump from one heading to another, replicating the experience of skimming a page visually."
"Low vision users often invert colors and use magnification levels as high as 400 percent to reduce eye strain."
"Alternative navigation users pick different tools based on the task and how they feel at that moment, not just one technology."
"In a usability session, the biggest challenge is not to talk at the same time the screen reader is talking."
"No assistive technology user uses default settings; we spend years customizing everything to work for us."
"The System Usability Scale’s question about needing a technical person to use the system is confusing and inaccurate for screen reader users."
"Most people with my assistive technology might learn to use the system at a different pace than non-disabled users."
"Screen reader users scored significantly lower in usability tests, reflecting the most effort in interpreting content."
"If you’re doing research with people with disabilities, consider using the Accessible Usability Scale to get more accurate insights."
Or choose a question:
More Videos
"No one is born knowing how to facilitate; it takes training, observation, and practice."
Alexandra SchmidtEnterprise UX Playbook
December 1, 2022
"The hiring process typically includes two manager screens and a final interview with project presentations."
Jen Crim Jess Quittner Saritha Kattekola Alex Karr Gurbani PahwaCulture, DIBS & Recruiting
June 11, 2021
"Product managers are responsible for value – making sure something valuable is being created that meets real needs."
Christian CrumlishAMA with Christian Crumlish, author of Product Management for UX People
March 24, 2022
"We turned design thinking on ourselves to tackle our own hiring challenges—applying tools meant for customers to our own processes."
Libby MaurerTreating Diversity & Inclusion in Hiring as a Design Problem
December 5, 2019
"Green spaces are not luxuries—they're necessities for urban life."
Ali Jeffery Sheri ChudowHow DesignOps Helped Enable Wall Street to Work Remotely
October 22, 2020
"We all say empathy is foundational for good design, yet contemporary research often remains oddly distant from real human experience."
Daniel GloydDesigning From the Inside Out: How Method Acting Can Inspire Design Research
February 12, 2026
"Learning should be an experience tailored around the learner, not the curriculum."
Kristin SkinnerFive Years of DesignOps
September 29, 2021
"Insights are unexpected discoveries about how things work and how to make them work better - Gary Klein."
Johanna KollmannInsights-Driven Product Strategy: Get your Research to Count
December 6, 2022
"Momentum in users is like energy in fluid—strong motivation drives fast, decisive movement."
David SternbergUncovering the hidden forces shaping user behavior
July 17, 2025
