Perceptual Blindness

Perceptual Blindness is a failure to notice a fully-visible, but unexpected object because attention was engaged on another task, event, or object.

Inattention Errors in Extemporaneous Writing


Automation provides many opportunities for inattention errors. Extemporaneous writing/typing is particularly prone to errors so egregious that they are funny… in retrospect. Here are a few examples of “scary” autocorrect mistakes as well as other problems caused by limited or spit [sorry, that was “split”] attention on the task of communication. 1. Everyone fails sometimes It is easy to fail when we are in a hurry, or are under pressure, or don’t proofread our work before it goes out. Some fails are the result of trying to be too clever and not getting a second opinion. Some fails are due to lack of process — a second pair of eyes on the copy would have noticed the “extra word” problem. Some fails are easily caught via a spellchecker… But in some cases, a spellchecker does help… And in many cases, spellcheck is the CAUSE of strange communications. I had a few of those myself… 2. Errors are different from mistakes Mistakes are things that we know are wrong the moment we notice them — the head-slappers! They are usually caused by inattention on the task. Errors are different. Errors result from true ignorance. But it doesn’t make the resulting fails…

Review eBook: Affordances and Design

Manches a Gigots

Victor Kaptelinin, a Professor at the Department of Information Science and Media Studies, University of Bergen, Norway, and the Department of Informatics, Umeaa University, Sweden, just published an eBook with Interaction Design Foundation: “Affordances and Design.” I was asked to write a review of this book and provide some insights into using affordances in interaction design and HCI. Let me start by providing the definition of affordance as given by Donald Norman: In his eBook, Victor Kaptelinin provides the history of the idea of affordance from its initial introduction by James Gibson in 1977 to the present day. The eBook’s bibliography and reference section is a great place to start the exploration of this topic for anyone new to these ideas. Unfortunately, the book doesn’t help much if an individual is looking for some guidance on how to apply these ideas in practical situations during interaction design or HCI design. For clarity’s sake, allow me to give a very brief explanation of affordances, from their roots to the present time. When James Gibson first introduced the concept of affordances, he focused on physical environment — what actions are possible? And the set of these action were invariable — just because…

Perceptual Focus Error

Early on in my academic career, I did research in a middle school classroom. Computers were just introduced to a bunch of kids that never experienced them directly before. There were very few computers in schools at the time, and students were bunched up in groups around each one. One kid got to sit and control the keyboard, another student controlled the mouse. (I bet you know the genders of these two kids.) Most kids just focused their attention on the screen. The task was to familiarize with how the desktop computer interface worked. At the end of the activity, I got to interview the kids. One of the surprises was how many of the kids didn’t associate the movement of the mouse with the action on the screen. To connect the two actions together, a kid would have had to know that mouse movements and a pointer were related. It was not an obvious observation, especially in a tight crowd of a student group around the computer screen. And to this day, this required double focus is difficult for kids on the Autistic spectrum (iPads are much more intuitive for this population). One of the conclusions of my study…

Where to post the “OK” Button on the Screen?

OK Button on Early Mac

I have very strong opinions about where on the screen the OK or NEXT or SUBMIT buttons go in relation to CANCEL. Without giving it away, I’m going to walk through the design decision tree and provide a lot of references for both sides of the issue — yes, there are strong feelings about the right versus the left position choice. I’m not alone! Passive versus Active Buttons Active Buttons are the ones that advance the action to the next level. Passive ones return the users to previous state, negate the action sequence. OKAY, OK, NEXT, SUBMIT, ACCEPT, GO are all active buttons. CANCEL, BACK, PREVIOUS are action that reverse forward momentum and push the user to places they’ve been before. HELP and INFO sidetrack the user and distract from forward thrust of activity. In general, product designers want to move the users toward their goals — thus we want the perceptual focus to be on the action buttons. We want to make sure that users fist see the way forward, and then click on the right button that propels them forward to completion of the task. All distractions and side movements should be downplayed with Interface Design with the…

p-Prims about Memory

Memory can be tricky—somethings seem to come to mind without bidding, while others are stubbornly evading our efforts at recalling them. We have many explanations for how and why somethings are easy to remember and others take so much effort; or why some people are very good at mnemonic feats and others not so much. Many of these mental models of how memory works are faulty (or simply not true) and are based on folksy wisdom passed from one generation to the next. Some of these wisdoms involve tricks for remembering things. For example, my Russian grandmother suggested tying corners of handkerchief to aide memory—if you notice a knot on the corner, you know that there’s something you supposed to remember. Since I don’t carry a handkerchief, I use my rings for the same effect—move a ring from finger to another (where it typically doesn’t belong) and then at least I know that should be keeping something in mind. Of course this strategy does nothing to help you remember what it is you are supposed to remember, but that’s another problem. So I thought to put together a little list of memory-related p-prims—a set of beliefs—that are common in our culture. Below,…

Attention Control Errors & Perceptual Blindness

Harvard Vision Lab created a few experiments that feature Attention Controls Errors and Perceptual Blindness. Below is one of their optical illusions. Directions: concentrate on the central white dot. Did the colors of the outside dots continue to shift throughout the video? If they stopped when the dots were rotating, then you’ve just experienced Silencing—the lab’s vocabulary for individual’s inability to pay attention to both motion and color shift at the same time. Here, we mostly call it Perceptual Blindness. My Personal Experience with this Illusion: The first time I watched the video, I think the colors stopped shifting…but I don’t really remember—I wasn’t paying attention! The second time, I saw the shift. When I showed the illusion to a colorblind individual, he saw the shift from the first viewing. To read about the complete experiment and to view more illusion videos, please visit the lab: