Understanding Usability

People who think that operating an eye tracker is hard, time consuming and requires lots of technical understanding are wrong.

If you can drive a usability testing tool like Morae or Silverback; or if you can drive a design program, then you can use eye tracking software. If you can create an online survey or roll out a social network you can use eye tracking software. So long as it it a Tobii eye tracker.

Here's two training videos on the Tobii Studio software:

If you want to use one at our EyeTrackLab for the day, let us know by emailing jbreeze@objectivedigital.com.

Of course, it is important that you have experience in usability test facilitation and setting up great research projects!

Visit our website for more user experience FAQs.

Loading mentions Retweet

We can help you with your social media strategy, set up the sites with some initial content and mentor you along the way.

Setting social media up, is reasonably easy:

• Research your market
• Choose your social networks
• Get some designs done
• Determine key words and content topics
• Create some initial content or reuse existing
• Connect the networks with each other and with your other marketing communications (e.g. website)

The challenge begins, when clients realise:

1. Who is going to create content ongoing?
2. How much content do we need ongoing?
3. How often do we need to update content?
4. How many resources do we need to handle this?

My response is:

1. Who is going to have conversations and create compelling content?
2. What are your customers interested in?
3. How often do your customers want to talk to you?
4. I have no idea, depends on how much you engage with people.

Your requirement for resources to manage social media will increase as soon as you start. The best way to overcome the exponential increase in resource requirement is to share the load around the organisation. Staff with different skills and interests, can help you cope with different situations, such as:

• geography and time zones
• customer types
• customer needs

Whilst social media can be great for marketing campaign, to see th real benefits you should modify your business processes so that they integrate social media. For example,

• Blogging to allow senior executives to communicate directly with customers   
• Social bookmarking to share key content amoungst staff and customers
• New products researched online with customers
• Some call centre communications facilitated through twitter
• Events organised through Facebook
• Advertising on Facebook
• Recruitment with LinkedIn
• Hosting your videos and images on YouTube and Flickr
• PR and media connections facilitated though online networks 
• Blogs for staff or customer communications instead of email, the list goes on. 

It's about culture change

The best way to handle this new customer and staff interaction mechanism is to change the culture of the organisation and have everyone doing it as part of their job. It should be taken seriously and staff should be rewarded for good use of social media (mainly customer interactions). 

Cultural change takes time and it's difficult. The best way to start is to identify people within the organisation who are great with people, who like the internet and who are enthusiastic about your business.  Some staff may never be able to do this, but that's ok, not everyone in an accountant and can balance your books.

Objective Digital will help you get your social media strategy right, kick start the process and mentor you through the cultural change. But we won't be tweeting for you for ever more. It is up to you to embed a way of doing things that supports this new business model.

 

Loading mentions Retweet

On June 22, 2010 Tobii launched a new revolutionary eye tracker: Tobii Glasses. This is the first head mounted, or wearable eye tracker from Tobii. Just like all of the other eye trackers from Tobii, Glasses is taking eye tracking to the next level. Unlike other wearable eye tracking systems Glasses is very lightweight (Glasses 75 grams plus recording assistant 200 grams), just like wearing a pair of sun glasses and an iPod. This is not the only revolutionary thing about Tobii:

Glasses, the real leap forward is the ease of use and the ability to aggregate eye tracking data which enables you to conduct quantitative eye tracking studies which is really unique for a wearable eye tracker.  To be able to do this Tobii has developed a new technology called AOA-Track with small markers that emits infrared light. By placing these IR-markers around objects and/or areas you want to study in depth, Tobii Glasses automatically knows when a person is looking within these areas and will automatically aggregate the data from all the participants in an eye tracking study. This is truly amazing! Previously when doing this kind of research it has required a lot of manual coding work to be able to do this, now it all happens automatically and you are able to use the analysis software Tobii Studio to analyze the data just as if it was recorded with a stationary eye tracker. In other words you can create visualizations like heat maps and gaze plots, calculate statistics etc automatically with data from a Tobii Glasses recording.

The device also includes a microphone and of course a camera filming everything the participant is looking at so it can also be used for qualitative studies (you just watch the recording as a video with the gaze point overlaid) and might even enable new research methodologies, what do you say about “Concurrent Think Aloud Walking” in usability research for example!

To learn more about the Tobii Glass please visit these resources online:

Video about how to use Tobii Glasses for Market Research:
http://www.tobiiglasses.com/marketresearch/

Video about how to use Tobii Glasses in Scientific Research:

http://www.tobiiglasses.com/scientificresearch/

Tobii Glasses Product Leaflet (pdf)

Tobii Glasses product page on Tobii.com here

Examples

These are some examples from Tobii Glasses recordings Tobii did in a Supermarket.

Watch a shopper in a supermarket being eye tracked in the YouTube video below

This is a Gaze Plot showing how a person is searching for a product on the shampoo shelf. IR-markers have been placed on the shelf to enable us to collect the data.

This is another shelf, the heat map shows the aggregated data from 30 recordings and reveals where people look when deciding which product to buy. IR-markers have been placed on the shelf (try to find them!) to enable us to aggregate the data and make this heat map.

YouTube video describing Tobii Glasses

Loading mentions Retweet

During the AIMIA Digital Customer Experience forum, that I chaired this morning, there was considerable discussion about how to justify the work UX people do and have it accepted as part of the business culture.  Difficulties with acceptance often occur in large enterprise where traditional cultures are strong and therefore it is difficult to update process. However, the landscape is changing.

I have been encouraged in recent years that enterprise has accepted the importance of customer (and staff) research during the product development process.  Companies like Telstra, Fairfax, Sensis, News Corp, Westpac, BT Financial and CBA have their own internal customer experience teams.  Most importantly, these teams are not just working on website and mobile apps. The great ones are shaping the entire business! UX Leads are overseeing product design, not just focussing on the digital bits. 

Another trend for these teams, that has been slow to take off in Australia, is the consideration of more than just the technology interaction during the design process.  Great UX teams are thinking about how the entier customer journey is 'designed'. Here's a concept from Opher Yom-Tov, from BT Financial and previously IDEO.

 

So how do companies make this happen?

One project at a time.
Don't use too many motherhood statements of user experience principles and try to preach them to the uninitiated. Instead do a project, do it properly and incorporate processes that engage users on the journey.  The outcomes will speak for themselves.

Inform.
Seb Chan from The PowerHouse Museum, reckons that sharing results of research is an important part of the UX sales process. Even if you don't have to, make sure that everyone knows that there is customer research available in a central repository (and that they can access it). The way that Seb encouraged sharing at the Powerhouse was to set up internal company blogs, where people began regularly sharing their insights from different projects. These blogs became so popular that they are now open to the World!

Teach.
Opher suggested that you should treat the project as an education process where the business and technical stakeholders and project team members are taught what UX design means and why it is important. At project team meetings let people know what they are there and what each step will do for the project. When customers are engaged in the project take photos, these will be useful later, when you need to show everyone what you did.

Once these projects are launched and the business sees success the exec will come round to the user experience way of thinking.

Loading mentions Retweet

Keep it simple.

Loading mentions Retweet

This is a copy of our UXMag.com guest post. Thanks UXMag!

Eye Tracking: Best Way to Test Rich App Usability | UX Magazine

Eye tracking has recently been debated on many fronts, with a particular focus on the ways people misuse it, and how some use eye tracking only as a way to "wow" clients. In our experience, however, it's invaluable in bringing to light key findings that are otherwise unattainable through other user testing methods. Eye tracking offers UX people the ability to:

• Leave a participant alone during a test to focus on the task at hand, and therefore
• Capture real physiological data about their conscious and unconscious experiences. This data is unique to eye tracking.

Eye Tracking for Rich Applications

Recently eye tracking has been heavily used in website design and testing. When I became involved about eight years ago, the sites tested were mainly flat HTML. Researchers were able to produce beautiful heat maps that were useful for comparing and optimising simple screen layouts and online advertising placements.

The invention of rich, interactive, and transactional interfaces, however, has meant producing eye tracking results is now more complex. Each interface has multiple states and people can interact in pretty much whatever way they like. People can choose their own way through a task to completion and the eye trackers can't tell which state is what as a person's eyes are tracked. Additional analysis is now required to separate these interactions, and fortunately eye tracking technologies have advanced to make this process relatively simple.

If this new level of sophisticated analysis is not achieved, this will result in eye tracking data being misused and eye tracking will retain (inappropriately) its novelty status.

Usability Testing Fraternities Lock Horns

Think Aloud

Think Aloud (TA) is an age-old usability testing method. People are asked to speak their thoughts, feelings, and opinions during a set of usability testing tasks. This is done with the help of the facilitator, who “skilfully interrupts" the process frequently to find out why people do particular things during the test.

In my opinion, when people are faced with lots of interactions on screen, considerable cognitive effort is required. Adding TA to this experience will inappropriately add more cognitive load to the task that would not normally be present. This can lead to misleading additional eye fixations and dwell times on outputs, which clouds the analysis. Often a poor facilitator will prompt users to the next stage (when was the last time someone knocked on your door and helped you find the right button when you browsed at home?), again spoiling the desired realism while testing.

We know there are three types of memory “storage" systems: sensory memory, short term, and long term. Our sensory memory retains an exact copy of what is seen or heard, and is generally thought to last between 300ms and a few seconds. Our short-term memory tends to remember between five and nine “items" (George Miller, et al) of information. If we start to talk about our actions in a TA protocol, these precious (milli) seconds and snapshots of information are quickly forgotten or overwritten. After that, what are they basing their commentary on?

Eye Tracking

There has been considerable debate about the usefulness of usability testing with eye tracking. Many TA proponents claim their methods, when carefully performed, will find enough issues compared with eye tracking, which they consider to be too difficult, time consuming, and expensive to bother about.

To my mind, this criticism arises from a situation where some people use eye tracking to make wild claims about how all websites should be designed. These can be found in numerous blog posts written that offer tips and guidelines. These include 23 Actionable Lessons From Eye-Tracking Studies, Web Form Design Guidelines: An Eyetracking Study, and Eyetracking Study Reveals 12 Website Tactics. These articles have been widely referenced and retweeted; however, they should be taken with a grain of salt. Without a clear understanding of the methodology used, the information should simply be seen as an investigative tool in your design process, not as the Holy Grail.

Of particular concern is Jakob Nielsen's F-pattern research. This was produced in 2006 and I regularly hear it mentioned in design meetings in Australia. This study was done using the regular TA protocol, which means that participants' eye gaze data is very likely not valid because they were talking to the experimenter during the study. Try doing an everyday task like driving, cooking, or cleaning while all along the way verbalising every little step, and see how your behaviour (actions, methods, or time to complete) is affected.

Retrospective Think Aloud

Retrospective Think Aloud is another usability testing method that has been used for many years. In this case, participants give their opinions of a task after it is completed and the interview is recorded for later reference. Of course, it is hard to remember what you did during a task.

Retrospective TA with eye tracking (RTA) is a method in which participants are quickly calibrated on the eye tracker and then asked to do the testing task without interruption from the facilitator. In fact, the facilitator can even leave the room during a test. Following the test, the facilitator immediately asks the participant to score their experience and then replays the eye gaze video of the participant's experience to them. This replay of their eye gaze triggers the person's memory of what they did, thereby mitigating the memory issue. Expanding on this, the eye gaze can also be removed to ask what the participant thought they looked at before revealing their actual interactions.

Think Eyetracking, an early adopter of the RTA eye tracking protocol (which they renamed PEEP), have published a jointly researched academic paper with Lancaster University, UK. Their academic article can be downloaded on the Think Eyetracking Blog. They also had a very popular blog post about it in 2008 that generated some controversy.

Below are some eye tracking heat maps created by Think Eyetracking that show a comparison of a Google search task done with TA (on the left) and RTA (on the right). Note the dramatic differences! It is obvious that the behaviour is very different, with long dwell times and numbers of fixations apparent in the TA output, probably caused by the participants staring at and browsing the screen while verbalising their actions.

Recently, Tobii Technology from Sweden created a unique feature in their Tobii Studio software where during the eye gaze replay stage of the test, the software records a video and audio record of the participant and facilitator as they review the eye tracking session. This can be paused, replayed, and scrubbed to allowing a full detailed analysis of the session with both visual and audio cues. Find out more about RTA on Scribd or watch this video:

Usability labs are set up to approximate real life. We regularly see experimenters set up their testing facilities like offices or lounge rooms to make the person feel at home. TA asks people to talk to someone while they are busy doing a task—where's the real life in that?

Eye tracking is the only real way to test a rich application without distracting the participant.

See Where People Looked, Not Where They Think They Looked

Here are some examples from our recent work at Objective Digital.

We allow people to complete tasks in a focused way, and also obtain real physiological data about what they are doing. It is difficult to argue with and almost impossible to fake these measures. We are not making assumptions about what they looked at and in what order things captured their attention. Some recent client projects encouraged us to use eye tracking to identify:

1. Where do people look first?
2. What don't they look at?
3. What they looked at before the usability issue occurred?
4. How people learn an interface?

1. Where Do People Look First?

Very simply, eye tracking can tell us exactly what caught people's attention first on a screen. Jay Eskenazi put this very clearly in a comment on the IxDA forum in 2009:

Eye tracking measures unconscious behavior—and provides data that people simply cannot verbalize in other common user research methods, especially TA usability testing protocols. Decades of psychology research show that much human behavior occurs at an unconscious level.

The human eye, for example, can make up to 5 fixations per second and this occurs below people's level of conscious awareness. So in a 30 second scan of a typical homepage, the customer may be looking at up to 150 items on the page. Your customers (or research participants) simply cannot verbally tell you where their eyes are going and this is exactly the value that good eye tracking data provides.

Our experience is that visual attention data IS correlated with behavioral performance metrics. If people don't "see" something, then they are less likely to click it.

2. What They Don't Look At

Case study 1: Eye tracking shows what things on the screen people didn't look at. Importantly, the data revealed what space was being wasted in the design and what areas of the page were essentially ignored.

Recently, when we tested an internal CRM application for a finance company, eye tracking proved that customer service staff ignored the very information the company wanted them to focus on. In the task, they weren't even required to click on the screen.

The image here shows clearly that in the first few seconds of usage staff focused primarily on the bottom right rather than the bottom left where they were meant to focus. This would not have been observable if simply interviewing them. Considering this screen is used 300,000 times per day, any improvements to the design that make the correct part of the screen more obvious will drive positive outcomes for the finance company's customer service.

Joanna Lewis, whom I work with, recently wrote a blog post about what people ignore.

3. What They Looked at Before the Usability Issue Occurred

Only with eye tracking can we see all the options that people consider, even unconsciously, before starting and completing a specific task.

Eye tracking shows you where people immediately look on a screen. Yes, they can find a target and do a usability task just fine. But where did they look first, especially for ecommerce where time taken can force customers to leave you or stay? Rob Tannen puts this very clearly:

[Eye tracking] does have value as a secondary diagnostic tool. In the context of usability testing, eye tracking does not determine the presence of a usability problem, but helps determine what led to that problem in conjunction with performance data, facilitator observations and user self-reporting.

Case study 2: As the video clearly shows, this user was looking everywhere except at the Donate area on the right. After looking at the navigation both at the side and at the top, the rest of the page was viewed but at no point did the user focus on the Donate area in the main image. It clearly highlights the fact that this call-to-action does not stand out in the prototype, and users are also expecting to see something within the navigation. Equally, the heat map below gives an indication where all six people we tested would expect to see this link.

Case study 3: When users were asked to change one of the options on this screen, the eye tracking heat map below showed very clearly where they were expecting to go. People did not see the areas they were supposed to (indicated in red). Eye tracking of the first second they looked at the screen allowed us to make the site more efficient as it clearly indicated where the functionality should have been positioned.

The heat map below shows the first second of eye tracking on a prototype applicaiton. Users were heavily fixated on one area of the screen, and it can be assumed that this is where they were expecting to find the function they were asked to look for (the buttons).

This experience can also be seen in our financial institution case study.

How Do People Learn an Interface?

Eye tracking is also useful for change management and training when a new system is introduced to staff within a business.

Where do people look the first time they see an application? How about the second time, and the third time? Eye tracking shows very clearly how people learn to interact with a system.

Case study 4:
A new user visiting the website

The new user is seen to skip back and forth between the right hand side panel and the selections and information on the main part of the page to complete the task.

A frequent user of the website

The frequent user skips back and forth less frequently than the new user and is more focused on completing the task.

An expert user of the website

The expert user is highly focused and directed and completes the task with minimum effort.

This example was again from the banking CRM case study. The client even used an eye tracking video as part of the training package for customer service reps. It was used to show them the best way to look at the interface the instant a customer identifies themselves at a branch.

Role-Played Customer Service

The eye tracking data gathered from the CRM examples above was gathered during a simulated customer service interaction. The bank branch staff member was tracked during a 45-minute role-played customer interview. Afterward, the usability issues were discussed when the staff member's eye gaze and screen interactions were replayed to him. I can't think of any other way to do this type of test that essentially involves three people: participant, role-played customer, and facilitator.

Commonly Reported Eye Tracking Advantages

Eye tracking offers unique advantages above and beyond traditional TA. Other widely known advantages include:

1. A more relaxed testing environment where participants give feedback in their own time, and actually find more usability errors.
2. Executives like eye tracking because it produces compelling physiological data that can't be argued with.
3. Real time eye tracking data also provides for a better observation experience. I frequently find that if I am observing a participant's gaze data in real time while they complete their tasks, I am better engaged and glean more detailed insights about the user interface.

In TA, sometimes it can be very hard to see what a person is talking about during the test. I once mentioned this to a TA proponent and they suggested that if the TA is managed well it wouldn't be a problem. During the test, they would have the test facilitator ask the participant to hover their mouse over the part of the screen they are describing so that the observers can see what is being discussed. I'm sorry, but this just means the participant gets even more distracted from the task at hand.

Loading mentions Retweet

Heuristic is a big word for a usability guideline and principle (best practice).Heuristics are used in the context of an Expert Usability Review (Heuristic Evaluation) to ensure that the user experience professional uses as a rule of thumb to uncover issues and create a usable website. 

I use the story of how my Honours thesis was edited to describe heuristics. The process took my editor friend, June, ages! When I asked. "Why did it take so long?" She responded "I read it 40 times?" "What? Why?", I said. "Don't you just read it through and pick up mistakes?"

The reason that my thesis was read so many times is that each time she read it, she had one single editing issue in mind.

• Grammar
• Spelling
• Capitalisation
• Fonts
• Image Titles
• Page numbers
• Style
• the list goes on.

She was using this technique to ensure coverage, to ensure that nothing was missed. 

I liken the expert usability review process to the editing process I experienced as an Honours student. Instead of 'reading' the website we use a set of carefully constructed tasks that represent what users would want to do with the technology, within the context of what the business is trying to achieve. Joanna recently blogged about how to create tasks.

As we go through the tasks the first time, issues that are observed can be noted down against each heuristic. Following this you can review the tasks again with an individual heuristic in mind as you go through each one.

According to Jakob Nielsen the 10 usability heuristics are:

• Visibility of system status
• Match between system and the real world
• User control and freedom
• Consistency and standards
• Error prevention
• Recognition rather than recall
• Flexibility and efficiency of use
• Aesthetic and minimalist design
• Help users recognize, diagnose, and recover from errors
• Help and documentation

These usability heuristics are representative of the most common issues for technology. However, sometimes it is necessary to use other ones at a more granular level. When we do an expert review we also use a long checklist against each of the heuristics.

You can read more about expert and oporutunity reviews on our website.

Loading mentions Retweet

Understanding eye tracking requires an insight into:

1. How the eye works?
2. Why the eye moves?
3. What do we study in eye tracking?
4. How do eye trackers work?

This content is taken from the Tobii blog that we administer and  white paper on Scribd.

1. How does the eye work?

Our eyes have many similarities with how a photo camera works: Light reflected from an object or a scene travels into our eyes through a lens. This lens concentrates and projects the light on to a light sensitive surface located on the back of a closed chamber. However, unlike a camera, the light sensitive surface (which in the eye is called the retina, see below) is not equally sensitive everywhere.

The retina is a light sensitive structure inside of the eye responsible for transforming light into signals, which are later converted into an image by the visual cortex in the brain. The fovea is a section of the retina that contains a high density of both kinds of light receptor cells found in the eye, i.e. Cone and Rod cells. Rod cells, which are mostly located in the outer retina, have low spatial resolution, support vision in low light conditions, do not discriminate colors, are sensitive to object movement and are responsible for the peripheral vision. Cone cells, which are densely packed within the central visual field, function best in bright light, process acute images and discriminate colors.

Through evolution, our eyes have been designed to work in both dark and light environments as well as providing both detail and quick changes in what we see. This has led to certain compromises, e.g., that we can only see details clearly in a limited part of our visual field (in the eye called the foveal area). The larger part of our visual field (the peripheral area) is better adapted to low light vision, and to detect movements and register contrasts between colors and shapes. The image produced by this area is blurry and less colorful. Between these two areas we find a region of transition called the para-foveal area, in which the image becomes gradually more blurry as we move from the fovea into the peripheral area (see below).

This figure is a schematic representation of the human visual field. The main area that is in focus, F, corresponds to the area where we direct our gaze to – the foveal area. As is illustrated in this image, the foveal area is not circular. Hence, the area in focus will have a slightly irregular shape as well. Within the rest of the visual field (the para‐foveal and peripheral areas) the image we perceive is blurry and thus harder to interpret and discriminate in high detail.

The cause of the differences in our visual field is the two different kinds of light receptor cells available in the eye, i.e. the rods and the cone cells. About 94% of the receptor cells in the eye are rods. As mentioned previously, the peripheral area of the retina is not very good at registering color and providing a sharp image of the world. This is because this area is mostly covered by rods. Rods do not require much light in order to work, but do, on the other hand, only provide a blurred and colorless image of our surroundings. For more detailed and clear vision, our eyes are also equipped with light receptor cells called cones which make up about 6% of the total number of light receptor cells in our eyes. Cones are, in the human eye, most often available in three different varieties; one that registers blue colors, one that registers green and one that registers red. While being efficient in providing a clear picture, the cones do require much more light in order to function. Hence, when we look at things when it’s dark around us, we lose the ability to see color and use mainly information registered by rods, providing us with a grey scale image. Cones are mostly found within the fovea where they are tightly packed in order to provide as clear an image as possible.

2. Why do our eyes move?

Often in articles on human vision and eye tracking accuracy, we come across measurements expressed in visual angle, e.g. the size of the foveal area is estimated to be 1-2° visual angle, or remote eye trackers have an accuracy between 1-0.5°. (Note: A smaller angle means less inaccuracy.) When we point a flashlight on a wall in a dark room we can observe that the light forms a projection on the wall. The size and shape of this projection is related to the size of the light source and the distance that you stand from the wall. The reason the distance affects the size of the projection is because the light disperses at a specific angle from the source. Hence, if we wish to specify the size of the projection area using a standard size measure (e.g. cm or cm2) of that flashlight we would always have to specify the distance at which it was measured. However, if we use the angle of dispersion as size indicator we can easily calculate the projection size for multiple distances using simple trigonometry. The same rationality applies to our visual field as images are formed through the projection of light on the retina, i.e. our eye works as a reversed flashlight that absorbs light instead of emitting it.

The human visual field spans about 220 degrees and is, as previously mentioned, divided in 3 main regions: foveal, parafoveal, and peripheral region. We primarily register visual data through the foveal region which constitutes less than 8% of the visual field.

Even though this represents only a small part of our field of vision, the information registered through the foveal region constitutes 50% of what is sent to the brain through our optic nerve. Our peripheral vision has a very poor acuity, which is illustrated above, and is only good for picking up movements and contrasts. Thus when we move our eyes to focus on a specific region of an image or object, we are essentially placing the foveal region of the eye on top of the area which is currently within main focus of the lens in our eye. This means that we are consequently maximizing our visual processing resources on that particular area of the visual field which also has the best image due to the optic characteristics of the eye. By letting the foveal region register the image, the brain get the highest resolution possible for the image of the interesting area to process as well as the most amount of data registered by the eye about that area. Hence, the brain is able to present the best possible image of the area we find interesting to us.

Click to view large

Rather than perceiving an object or a scene as a whole we fixate on relevant features that attract our visual attention, and construct the scene in our visual cortex using the information acquired during those fixations.

Eye movements have 3 main functions which are considered important when we process visual information:

1. Place the information that interests us on the fovea. To do this, fixations and saccades are used. A fixation is the pause of the eye movement on a specific area of the visual field; and saccades the rapid movements between fixations.
2. Keep the image stationary on the retina in spite of movements of the object or one’s head. This movement is commonly called a smooth pursuit.
3. Prevent stationary objects from fading perceptually. Movements used for this are called microsaccades, tremors and drift.

3. What do we study when we use eye tracking data?

What is visual attention?

Whenever we look at the world, we consciously or unconsciously focus only on a fraction of the total information that we could potentially process, in other words we perform a perceptual selection process called attention. Visually this is most commonly done by moving our eyes from one place of the visual field to another; this process is often referred to as a change in overt attention – our gaze follows our attention shift. Even though we prefer to move our eyes to shift our attention, we are also capable to move our mind’s attention to the peripheral areas of our visual field without eye movements. This mechanism is called covert attention. Although we can use these two mechanisms separately they most frequently occur together. An example is when we are looking at a city landscape and we first use our covert attention to detect a shape or movement in our visual field that appears to be interesting and use our peripheral vision to roughly identify what it is. We then direct our gaze to that location allowing our brain to access more detailed information. Thus a shift of our overall attention is commonly initiated by our covert attention quickly followed by a shift of our overt attention and the corresponding eye movements.

How fast is human visual perception?

In addition to only having a very limited sharp field of vision, our eyes are also fairly slow at registering changes in images compared to the update frequency of a modern computer screen. Research has shown that the retina needs about 80 ms of seeing a new image before that image is registered in normal light conditions. This doesn’t mean that we consciously have noticed any changes – only that the eye has registered a change. The ability to register an image is also dependent on the light intensity of that image. This can be compared with a photographic camera where a short shutter speed, in a badly lit environment results in a dark and blurred image, where hardly anything can be seen. However, if taking an image of something which is very well lit, e.g. a window, the shutter speed can be very short without this problem occurring. In addition to needing time to register an image, the eye also requires time for the image to disappear from the retina. This is also dependent on the light intensity. One example of this is when being exposed to a very bright light such as a camera flash where the image of the flash stays on the retina long after the flashing has ended.

In addition to the light sensitivity of the eye, how fast we perceive something we are looking at also depends on what we are observing. When reading in normal light conditions, it has been observed that most people only need between 50-60 ms of seeing a word in order to perceive it. However, when looking at, e.g., a picture people need to see it for more than 150 ms before being able to interpret what they are seeing.

Most eye tracking studies aim to identify and analyze patterns of visual attention of individuals when performing specific tasks (e.g. reading, searching, scanning an image, driving, etc.). In these studies eye movements are typically analyzed in terms of fixations and saccades. During each saccade visual acuity is suppressed and, as a result, we are unable to see at all. We perceive the world visually only through fixations. The brain virtually integrates the visual images that we acquire through successive fixations into a visual scene or object (see the image above). Furthermore we are only able to combine features into an accurate perception when we fixate and focus our attention on them. The more complicated, confusing or interesting those features are the longer we need to process them and, consequently, more time is spent fixating on them. In most cases we can only perceive and interpret something clearly when we fixate on an object or are very close to it. This eye–mind relationship is what makes it possible to use eye movement measurements to tell something about human behavior.

4. How do eye trackers work?

The process of eye tracking is, from a technical point of view, divided into two different parts: registering the eye movements and presenting them to the user in a meaningful way. While the eye tracker records the eye movements sample by sample, the software running on the computer is responsible for interpreting the fixations within the data. This blogpost aims at explaining the principles used in Tobii Eye Trackers in order to track the participant’s eye movements.

Pupil Centre Corneal Reflection technique (PCCR) A light source is used to cause reflection patterns on the cornea and pupil of the test person. A camera will then be used to capture an image of the eye. The direction of the gaze is then calculated using the angles and distances.

How are the eye movements tracked?

Eye tracking has long been known and used as a method to study the visual attention of individuals. There are several different techniques to detect and track the movements of the eyes. However, when it comes to remote, non‐intrusive, eye tracking the most commonly used technique is Pupil Centre Corneal Reflection (PCCR). The basic concept is to use a light source to illuminate the eye causing highly visible reflections, and a camera to capture an image of the eye showing these reflections. The image captured by the camera is then used to identify the reflection of the light source on the cornea (glint) and in the pupil. We are then able to calculate a vector formed by the angle between the cornea and pupil reflections – the direction of this vector, combined with other geometrical features of the reflections, will then be used to calculate the gaze direction. The Tobii Eye Trackers are an improved version of the traditional PCCR remote eye tracking technology (US Patent US7,572,008). Near infrared illumination is used to create the reflection patterns on the cornea and pupil of the eye of a user and two image sensors are used to capture images of the eyes and the reflection patterns. Advanced image processing algorithms and a physiological 3D model of the eye are then used to estimate the position of the eye in space and the point of gaze with high accuracy.

Eye during Brigh pupil eye tracking. Above to the left is a Hispanic or Caucasian eye. Above to the right is an Asian eye.

Eye during Dark pupil eye tracking. Above to the left is a Hispanic or Caucasian eye. Above to the right is an Asian eye.

What are Dark and Bright Pupil eye tracking?

There are two different illumination setups that can be used with PCCR eye tracking: bright pupil eye tracking, where an illuminator is placed close to the optical axis of the imaging device, which causes the pupil to appear lit up (this is the same phenomenon that causes red eyes in photos); and dark pupil eye tracking where the illuminator is placed away from the optical axis causing the pupil to appear darker than the iris.

There are different factors that can affect the pupil detection during remote eye tracking when using each one of these two techniques. For example, when using the bright pupil method, factors that affect the size of the pupil, such as age and environmental light, may have an impact on trackability of the eye. Ethnicity is also another factor that affects the bright/dark pupil response: For Hispanics and Caucasians the bright pupil method works very well. However, the method has proven to be less suitable when eye tracking Asians for whom the dark pupil method provides better trackability.

Tobii Eye Trackers of the T/X Series use both bright and dark pupil methods to calculate the gaze position while the earlier 50‐series only used dark pupil eye tracking. Hence, the Tobii T/X Series Eye Trackers are able to deal with larger variations in experimental conditions and ethnicity than an eye tracker using only one of the techniques described above. All participants are initially subjected to both the bright and dark pupil methods and the method that is found to provide the highest accuracy is chosen for the actual testing. During a recording the Tobii TX‐Series Eye Trackers do not change between bright and dark pupil tracking unless conditions change in a way that have a significantly negative impact on trackability. If that happens, the Tobii Eye Trackers conduct a new test where both methods are used simultaneously in order to determine which method is the most suitable for the new conditions and continue the recording using only the selected method.

Wow! that was a long post. Eye tracking is pretty complex! Thanks Tobii!

Read other FAQs about eye tracking on our Objective Digtial website.

Loading mentions Retweet

"They're Too complicated!"

That’s the most common mistake we see in tasks for a usability test. You want the test participant to focus on the website, not the tasks. Too complicated and the participant will be interacting with you, not with the website. Plus, when they'll keep forgetting the task if it is too long.http://img.skitch.com

 

These are our 10 guidelines for developing simple, effective and uncomplicated tasks for a usability test:

1 Relate each task to test objective

You don’t have many opportunities – generally only 1 hour with the participant, so keep the task focused on the purpose of the test. If the purpose is to test whether users can complete an order, get them to do just that. You should be able to tick off each of the test objectives against a task.

2 Select scenarios that rate high on frequency and/or importance

You may have only 6-8 tasks in a test, so focus on the important tasks. Find something and check out.

For a new site, you generally want to test the primary purpose of the site – find a product and check out, sign up for something, find the answer to something.

3 Don’t make them too complicated

We've said it before, but its important. Keep it simple, preferably to one or two sentences:

Example: You want to book a holiday for your family. Find a holiday that suits you.

4 Be as realistic as possible

Try to make the task suit the participant’s real life circumstances. That’s why you have recruited them against certain criteria. For example, don’t have people look for a holiday for an imaginary family – get them to use their own family or friends.

If you have very different user groups, say, Customer and Advisers on a banking site, you need two sets of tasks. One for each group.

5 Move from general to specific

You don’t want to lead the participant around the website by the sequence of tasks. It’s better to have an open exploratory task first to see how the participant interacts with the website.  Then, move to the more specific tasks, based on the objectives and the new functionality.

6 Avoid using the words on the website

Using words on the website leads people. Try to write the task in everyday language.

Example: You want to take out your superannuation NOT You want to consolidate your super.

7 Use concrete language

As much as possible, use active verbs to describe the task - Book a hotel in Rome; Buy a Xmas present for your partner; Find out the weather forecast for today.

8 Follow a logical flow through the website

Try to make the test follow a natural customer journey from start to finish. For example, on an e-commerce site, the customer may explore, compare, purchase, create an account, and check out. Your test should follow this sequence.

9 For information tasks, instruct the participant on how to end

Don't leave the participant floundering when they have reached the end of the task. Have the participant tell the facilitator when they have found the answer.

Example: Find a cruise which interests you. Tell the facilitator when you have found it.

10 Utilise other communications

Showing the participant other product material such as brochures, leaflets or ads can be useful if you don’t want to explain too much in a task. Then it is up to the participant to work it out from the website, and the extra material.

Example: You saw this ad on a bus stop. Find out if this product would suit you.

Of course, we will write the tasks with you!

Feel free to read more usability FAQs on our website.

Loading mentions Retweet