Modelling Error Rates in Temporal Pointing
Quantifying Efficiency of Input Methods
/
Lee, Byungjoo
/
Oulasvirta, Antti
Proceedings of the ACM CHI'16 Conference on Human Factors in Computing
Systems
2016-05-07
v.1
p.1857-1868
© Copyright 2016 ACM
Summary: We present a novel model to predict error rates in temporal pointing. With
temporal pointing, a target is about to appear within a limited time window for
selection. Unlike in spatial pointing, there is no movement to control in the
temporal domain; the user can only determine when to launch the response.
Although this task is common in interactions requiring temporal precision,
rhythm, or synchrony, no previous HCI model predicts error rates as a function
of task properties. Our model assumes that users have an implicit point of aim
but their ability to elicit the input event at that time is hampered by
variability in three processes: 1) an internal time-keeping process, 2) a
response-execution stage, and 3) input processing in the computer. We derive a
mathematical model with two parameters from these assumptions. High fit is
shown for user performance with two task types, including a rapidly paced game.
The model can explain previous findings showing that touchscreens are much
worse in temporal pointing than physical input devices. It also has novel
implications for design that extend beyond the conventional wisdom of
minimising latency.
Free-Form Gesture Authentication in the Wild
Smartphone Authentication
/
Yang, Yulong
/
Clark, Gradeigh D.
/
Lindqvist, Janne
/
Oulasvirta, Antti
Proceedings of the ACM CHI'16 Conference on Human Factors in Computing
Systems
2016-05-07
v.1
p.3722-3735
© Copyright 2016 ACM
Summary: Free-form gesture passwords have been introduced as an alternative mobile
authentication method. Text passwords are not very suitable for mobile
interaction, and methods such as PINs and grid patterns sacrifice security over
usability. However, little is known about how free-form gestures perform in the
wild. We present the first field study (N=91) of mobile authentication using
free-form gestures, with text passwords as a baseline. Our study leveraged
Experience Sampling Methodology to increase ecological validity while
maintaining control of the experiment. We found that, with gesture passwords,
participants generated new passwords and authenticated faster with comparable
memorability while being more willing to retry. Our analysis of the gesture
password dataset indicated biases in user-chosen distribution tending towards
common shapes. Our findings provide useful insights towards understanding
mobile device authentication and gesture-based authentication.
How We Type: Movement Strategies and Performance in Everyday Typing
Fingers and Technology
/
Feit, Anna Maria
/
Weir, Daryl
/
Oulasvirta, Antti
Proceedings of the ACM CHI'16 Conference on Human Factors in Computing
Systems
2016-05-07
v.1
p.4262-4273
© Copyright 2016 ACM
Summary: This paper revisits the present understanding of typing, which originates
mostly from studies of trained typists using the ten-finger touch typing
system. Our goal is to characterise the majority of present-day users who are
untrained and employ diverse, self-taught techniques. In a transcription task,
we compare self-taught typists and those that took a touch typing course. We
report several differences in performance, gaze deployment and movement
strategies. The most surprising finding is that self-taught typists can achieve
performance levels comparable with touch typists, even when using fewer
fingers. Motion capture data exposes 3 predictors of high performance: 1)
unambiguous mapping (a letter is consistently pressed by the same finger), 2)
active preparation of upcoming keystrokes, and 3) minimal global hand motion.
We release an extensive dataset on everyday typing behavior.
HCI Research as Problem-Solving
Problem-solving or not? The Boundaries of HCI Research
/
Oulasvirta, Antti
/
Hornbæk, Kasper
Proceedings of the ACM CHI'16 Conference on Human Factors in Computing
Systems
2016-05-07
v.1
p.4956-4967
© Copyright 2016 ACM
Summary: This essay contributes a meta-scientific account of human-computer
interaction (HCI) research as problem-solving. We build on the philosophy of
Larry Laudan, who develops problem and solution as the foundational concepts of
science. We argue that most HCI research is about three main types of problem:
empirical, conceptual, and constructive. We elaborate upon Laudan's concept of
problem-solving capacity as a universal criterion for determining the progress
of solutions (outcomes): Instead of asking whether research is 'valid' or
follows the 'right' approach, it urges us to ask how its solutions advance our
capacity to solve important problems in human use of computers. This offers a
rich, generative, and 'discipline-free' view of HCI and resolves some existing
debates about what HCI is or should be. It may also help unify efforts across
nominally disparate traditions in empirical research, theory, design, and
engineering.
Spotlights: Attention-Optimized Highlights for Skim Reading
Eye Gaze
/
Lee, Byungjoo
/
Savisaari, Olli
/
Oulasvirta, Antti
Proceedings of the ACM CHI'16 Conference on Human Factors in Computing
Systems
2016-05-07
v.1
p.5203-5214
© Copyright 2016 ACM
Summary: The paper contributes a novel technique that can improve user performance in
skim reading. Users typically use a continuous-rate-based scrolling technique
to skim works such as longer Web pages, e-books, and PDF files. However, visual
attention is compromised at higher scrolling rates because of motion blur and
extraneous objects with overly brief exposure times. In response, we present
Spotlights. It complements the regular continuous technique at high speeds
(2-20 pages/s). We present a novel design rule informed by theories of the
human visual system for dynamically selecting objects and placing them on
transparent overlays on top of the viewer. This improves the quality of visual
processing at high scrolling rates by 1) limiting the number of objects, 2)
ensuring minimal processing time per object, and 3) keeping objects static to
avoid motion blur and facilitate gaze deployment. Spotlights was compared to
continuous scrolling in two studies using long documents (200+ pages).
Comprehension levels for long documents were comparable with those in
continuous-rate-based scrolling, but Spotlights showed significantly better
scrolling speed, gaze deployment, recall, lookup performance, and user-rated
comprehension.
Rethinking Mobile Interfaces for Older Adults
SIG Meetings
/
Charness, Neil
/
Dunlop, Mark
/
Munteanu, Cosmin
/
Nicol, Emma
/
Oulasvirta, Antti
/
Ren, Xiangshi
/
Sarcar, Sayan
/
Silpasuwanchai, Chaklam
Extended Abstracts of the ACM CHI'16 Conference on Human Factors in
Computing Systems
2016-05-07
v.2
p.1131-1134
© Copyright 2016 ACM
Summary: This SIG advances the study of mobile user interfaces for the aging
population. The topic is timely, as the mobile device has become the most
widely used computer terminal and at the same time the number of older people
will soon exceed the number of children worldwide. However, most HCI research
addresses younger adults and has had little impact on older adults. Some design
trends, like the mantra "smaller is smarter", contradict the needs of older
users. Developments like this may diminish their ability to access information
and participate in society. This can lead to further isolation (social and
physical) of older adults and increased widening of the digital divide. This
SIG aims to discuss mobile interfaces for older adults. The SIG has three
goals: (i) to map the state-of-art, (ii) to build a community gathering experts
from related areas, and (iii) to raise awareness within the SIGCHI community.
The SIG will be open to all at CHI.
Computational Layout Perception using Gestalt Laws
Late-Breaking Works: Designing Interactive Systems
/
Koch, Janin
/
Oulasvirta, Antti
Extended Abstracts of the ACM CHI'16 Conference on Human Factors in
Computing Systems
2016-05-07
v.2
p.1423-1429
© Copyright 2016 ACM
Summary: We present preliminary results on computational perception of interactive
layouts. Our goal is to algorithmically estimate how users perceive a layout.
Potential applications range from automated usability evaluation to
computer-generated and adaptive interfaces. Layout perception is challenging,
however, because of diverse features, combinatorial complexity, and absence of
approaches. We have explored Gestalt laws as parsing heuristics. Our approach
finds a parametrization that optimally resolves conflicts among competing
interpretations of a layout. The output is a hierarchical grouping of main
elements. The results are promising: an implementation of just four Gestalt
laws enables hierarchical grouping that presents promising results in 90% of
our (realistic) test cases.
Sketchplore: Sketch and Explore Layout Designs with an Optimiser
Interactivity Demos
/
Todi, Kashyap
/
Weir, Daryl
/
Oulasvirta, Antti
Extended Abstracts of the ACM CHI'16 Conference on Human Factors in
Computing Systems
2016-05-07
v.2
p.3780-3783
© Copyright 2016 ACM
Summary: Sketchploration is a novel concept of integrating real-time design
optimisation to sketching tools, to enable interactive exploration of design
alternatives. Although traditional optimisation methods can attack very complex
design problems, their insistence on precise objectives contradicts sketching.
Sketchplorer is an interactive sketching tool that uses a real-time layout
optimiser. It automatically infers the designer's task and searches for local
improvements, and global alternatives. Using several predictive models of user
performance and perception, its suggestions steer designers toward more usable
and aesthetic layouts. This facilitates the creative and problem-solving
aspects of sketching, without requiring extensive intervention from the
designer.
Beyond Relevance: Adapting Exploration/Exploitation in Information Retrieval
Information Retrieval and Search
/
Athukorala, Kumaripaba
/
Medlar, Alan
/
Oulasvirta, Antti
/
Jacucci, Giulio
/
Glowacka, Dorota
Proceedings of the 2016 International Conference on Intelligent User
Interfaces
2016-03-07
v.1
p.359-369
© Copyright 2016 ACM
Summary: We present a novel adaptation technique for search engines to better support
information-seeking activities that include both lookup and exploratory tasks.
Building on previous findings, we describe (1) a classifier that recognizes
task type (lookup vs. exploratory) as a user is searching and (2) a
reinforcement learning based search engine that adapts accordingly the balance
of exploration/exploitation in ranking the documents. This allows supporting
both task types surreptitiously without changing the familiar list-based
interface. Search results include more diverse results when users are exploring
and more precise results for lookup tasks. Users found more useful results in
exploratory tasks when compared to a base-line system, which is specifically
tuned for lookup tasks.
Performance and Ergonomics of Touch Surfaces: A Comparative Study using
Biomechanical Simulation
Understanding & Extending Touch Interfaces
/
Bachynskyi, Myroslav
/
Palmas, Gregorio
/
Oulasvirta, Antti
/
Steimle, Jürgen
/
Weinkauf, Tino
Proceedings of the ACM CHI'15 Conference on Human Factors in Computing
Systems
2015-04-18
v.1
p.1817-1826
© Copyright 2015 ACM
Summary: Although different types of touch surfaces have gained extensive attention
in HCI, this is the first work to directly compare them for two critical
factors: performance and ergonomics. Our data come from a pointing task (N=40)
carried out on five common touch surface types: public display (large,
vertical, standing), tabletop (large, horizontal, seated), laptop (medium,
adjustably tilted, seated), tablet (seated, in hand), and smartphone (single-
and two-handed input). Ergonomics indices were calculated from biomechanical
simulations of motion capture data combined with recordings of external forces.
We provide an extensive dataset for researchers and report the first analyses
of similarities and differences that are attributable to the different postures
and movement ranges.
iSkin: Flexible, Stretchable and Visually Customizable On-Body Touch Sensors
for Mobile Computing
Using Random Body Parts for Input
/
Weigel, Martin
/
Lu, Tong
/
Bailly, Gilles
/
Oulasvirta, Antti
/
Majidi, Carmel
/
Steimle, Jürgen
Proceedings of the ACM CHI'15 Conference on Human Factors in Computing
Systems
2015-04-18
v.1
p.2991-3000
© Copyright 2015 ACM
Summary: We propose iSkin, a novel class of skin-worn sensors for touch input on the
body. iSkin is a very thin sensor overlay, made of biocompatible materials, and
is flexible and stretchable. It can be produced in different shapes and sizes
to suit various locations of the body such as the finger, forearm, or ear.
Integrating capacitive and resistive touch sensing, the sensor is capable of
detecting touch input with two levels of pressure, even when stretched by 30%
or when bent with a radius of 0.5cm. Furthermore, iSkin supports single or
multiple touch areas of custom shape and arrangement, as well as more complex
widgets, such as sliders and click wheels. Recognizing the social importance of
skin, we show visual design patterns to customize functional touch sensors and
allow for a visually aesthetic appearance. Taken together, these contributions
enable new types of on-body devices. This includes finger-worn devices,
extensions to conventional wearable devices, and touch input stickers, all
fostering direct, quick, and discreet input for mobile computing.
Investigating the Dexterity of Multi-Finger Input for Mid-Air Text Entry
Mid-Air Gestures and Interaction
/
Sridhar, Srinath
/
Feit, Anna Maria
/
Theobalt, Christian
/
Oulasvirta, Antti
Proceedings of the ACM CHI'15 Conference on Human Factors in Computing
Systems
2015-04-18
v.1
p.3643-3652
© Copyright 2015 ACM
Summary: This paper investigates an emerging input method enabled by progress in hand
tracking: input by free motion of fingers. The method is expressive,
potentially fast, and usable across many settings as it does not insist on
physical contact or visual feedback. Our goal is to inform the design of
high-performance input methods by providing detailed analysis of the
performance and anatomical characteristics of finger motion. We conducted an
experiment using a commercially available sensor to report on the speed,
accuracy, individuation, movement ranges, and individual differences of each
finger. Findings show differences of up to 50% in movement times and provide
indices quantifying the individuation of single fingers. We apply our findings
to text entry by computational optimization of multi-finger gestures in
mid-air. To this end, we define a novel objective function that considers
performance, anatomical factors, and learnability. First investigations of one
optimization case show entry rates of 22 words per minute (WPM). We conclude
with a critical discussion of the limitations posed by human factors and
performance characteristics of existing markerless hand trackers.
The Emergence of Interactive Behavior: A Model of Rational Menu Search
Interacting with GUIs
/
Chen, Xiuli
/
Bailly, Gilles
/
Brumby, Duncan P.
/
Oulasvirta, Antti
/
Howes, Andrew
Proceedings of the ACM CHI'15 Conference on Human Factors in Computing
Systems
2015-04-18
v.1
p.4217-4226
© Copyright 2015 ACM
Summary: One reason that human interaction with technology is difficult to understand
is because the way in which people perform interactive tasks is highly
adaptive. One such interactive task is menu search. In the current article we
test the hypothesis that menu search is rationally adapted to (1) the
ecological structure of interaction, (2) cognitive and perceptual limits, and
(3) the goal to maximise the trade-off between speed and accuracy. Unlike in
previous models, no assumptions are made about the strategies available to or
adopted by users, rather the menu search problem is specified as a
reinforcement learning problem and behaviour emerges by finding the optimal
Markov Decision Process (MDP). The model is tested against existing empirical
findings concerning the effect of menu organisation and menu length. The model
predicts the effect of these variables on task completion time and eye
movements. The discussion considers the pros and cons of the modelling approach
relative to other well-known modelling approaches.
Text Entry on the Edge
Workshop Summaries
/
Clawson, James
/
Arif, Ahmed Sabbir
/
Brewster, Stephen
/
Dunlop, Mark
/
Kristensson, Per Ola
/
Oulasvirta, Antti
Extended Abstracts of the ACM CHI'15 Conference on Human Factors in
Computing Systems
2015-04-18
v.2
p.2381-2384
© Copyright 2015 ACM
Summary: The primary focus of our workshop is to challenge the expanding text entry
community to move beyond the mobile phone and start exploring novel and
emerging technologies, designing systems for non-traditional users, and expand
into unexplored domains and contexts of use. We hope to engage in setting a new
agenda for our research community through the identification, collection, and
presentation of text entry edge cases. As such, our workshop has two specific
foci. First, to strengthen the text entry community by bringing text entry
researchers working in various disciplines together in hopes of sharing
knowledge across disciplines and establishing a set of best practices that can
be used to build our community. Second, to set a research agenda around these
edge cases that can be used to drive the field forwards and unite the field in
a common direction so that our combined efforts can help bring novel and
impactful text entry solutions to new and emerging technologies as well as
underserved communities of users and research domains.
What to Study in HCI?
Workshop Summaries
/
Hornbæk, Kasper
/
Oulasvirta, Antti
/
Reeves, Stuart
/
Bødker, Susanne
Extended Abstracts of the ACM CHI'15 Conference on Human Factors in
Computing Systems
2015-04-18
v.2
p.2385-2388
© Copyright 2015 ACM
Summary: The question "What to Study in HCI" has two parts. First it asks how HCI
researchers think about the research challenges they tackle: how do they decide
what problems to engage with and how to study them? Second, the question also
asks what is the subject of HCI: which challenges should researchers address
and, ultimately, what makes us unique as a discipline? While there have been
intermittent discussions on this topic in HCI, the present workshop emphasizes
this question and explore some possible answers among a group of seasoned
researchers. One reason is our belief that researchers can benefit from
addressing these questions so as to develop their practical understanding
(e.g., "tricks of the trade") of how to tackle the complexity of selecting
"what to study". Second, we argue that researchers can benefit from thinking
about the epistemological grounds upon which they base their everyday work,
that is, thinking about what HCI is. The workshop results in publicly available
key readings and position papers on "What to Study in HCI".
Principles, Techniques and Perspectives on Optimization and HCI
Workshop Summaries
/
Kristensson, Per Ola
/
Bi, Xiaojun
/
Howes, Andrew
/
Oulasvirta, Antti
/
Murray-Smith, Roderick
/
Thimbleby, Harold
/
Williamson, John
/
Zhai, Shumin
Extended Abstracts of the ACM CHI'15 Conference on Human Factors in
Computing Systems
2015-04-18
v.2
p.2441-2444
© Copyright 2015 ACM
Summary: We propose a workshop on the rapidly emerging topic of optimization and
computational design in human-computer interaction (HCI). The workshop will
tackle the following perspectives: defining and eliciting optimality criteria,
optimizing at scale, optimization and user models, optimization for safety,
optimization and design practice, optimization and users' perception of
performance, and critical perspectives.
Informing the Design of Novel Input Methods with Muscle Coactivation
Clustering
Special Issue on Physiological Computing for Human-Computer Interaction
/
Bachynskyi, Myroslav
/
Palmas, Gregorio
/
Oulasvirta, Antti
/
Weinkauf, Tino
ACM Transactions on Computer-Human Interaction
2015-01
v.21
n.6
p.30
© Copyright 2015 ACM
Summary: This article presents a novel summarization of biomechanical and performance
data for user interface designers. Previously, there was no simple way for
designers to predict how the location, direction, velocity, precision, or
amplitude of users' movement affects performance and fatigue. We cluster muscle
coactivation data from a 3D pointing task covering the whole reachable space of
the arm. We identify 11 clusters of pointing movements with distinct muscular,
spatio-temporal, and performance properties. We discuss their use as heuristics
when designing for 3D pointing.
Narrow or Broad?: Estimating Subjective Specificity in Exploratory Search
IR Session 7: Exploratory Search
/
Athukorala, Kumaripaba
/
Oulasvirta, Antti
/
Glowacka, Dorota
/
Vreeken, Jilles
/
Jacucci, Giulio
Proceedings of the 2014 ACM Conference on Information and Knowledge
Management
2014-11-03
p.819-828
© Copyright 2014 ACM
Summary: Supporting exploratory search is a very challenging problem, not least
because of the dynamic nature of the exercise: both the knowledge and interests
of the user are subject to constant change. Moreover, whether the results for a
query are informative is strongly subjective. What is informative to one user,
is too specific for the other; specificity differs between users depending on
their intent and accumulated knowledge about the domain.
We propose a formal model -- motivated by Information Foraging Theory -- for
predicting the subjective specificity of search results based on simple
observables such as result-clicks. Through two studies including both
controlled and free-form exploratory search we show our model allows us to
differentiate between levels of subjective result specificity with regard to
the current information need of the user.
Demo hour
Demo hour
/
Dauner, Joanna Maria
/
Karagozler, Emre
/
Glisson, Matthew
/
Speed, Chris
/
Hartswood, Mark
/
Laurier, Eric
/
Magee, Siobhan
/
Tynan-O'Mahony, Fionn
/
de Jode, Martin
/
Hudson-Smith, Andrew
/
Harriman, Jiffer
/
Feit, Anna Maria
/
Oulasvirta, Antti
interactions
2014-11
v.21
n.6
p.8-11
© Copyright 2014 ACM
Summary: During DIS 2014 Experience Night, conference attendees experienced a
thought-provoking set of interactive systems, artworks, and techno-crafts. We
selected interactive works that explore the reemergence of craft in the design
of interactive systems, the role of craft in democratizing design, and the role
of makers in interactive technology design. Alissa Antle and Steven Dow, DIS
2014 Demo Chairs
Mixed feelings?: the relationship between perceived usability and user
experience in the wild
/
Raita, Eeva
/
Oulasvirta, Antti
Proceedings of the 8th Nordic Conference on Human-Computer Interaction
2014-10-26
p.1-10
© Copyright 2014 ACM
Summary: Although both user experience and perceived usability have been extensively
studied, the relationship between the two is less well understood. Prior
empirical research suggests that perceived usability influences especially
negative user experiences, but the effect depend on goals, contexts, and
expectations. The paper contributes on this theme with description of a field
study covering self-reporting of 12 subjects using a new smartphone. The
findings confirm some earlier views on the relationship but also permit a
richer understanding. Unlike prior work, the results show that perceived
usability can play an important role in ambivalent experiential episodes. These
episodes emerge from a clash between desired uses and either poor perceived
usability or lack of appropriateness in the broader social context. We discuss
our findings in relation to prior studies.
Improvements to keyboard optimization with integer programming
Input techniques
/
Karrenbauer, Andreas
/
Oulasvirta, Antti
Proceedings of the 2014 ACM Symposium on User Interface Software and
Technology
2014-10-05
v.1
p.621-626
© Copyright 2014 ACM
Summary: Keyboard optimization is concerned with the design of keyboards for
different terminals, languages, user groups, and tasks. Previous work in HCI
has used random search based methods, such as simulated annealing. These "black
box" approaches are convenient, because good solutions are found quickly and no
assumption must be made about the objective function. This paper contributes by
developing integer programming (IP) as a complementary approach. To this end,
we present IP formulations for the letter assignment problem and solve them by
branch-and-bound. Although computationally expensive, we show that IP offers
two strong benefits. First, its structured non-random search approach improves
the outcomes. Second, it guarantees bounds, which increases the designer's
confidence over the quality of results. We report improvements to three
keyboard optimization cases.
Toward optimal menu design
Features
/
Bailly, Gilles
/
Oulasvirta, Antti
interactions
2014-07
v.21
n.4
p.40-45
© Copyright 2014 ACM
PianoText: redesigning the piano keyboard for text entry
Performing interactions
/
Feit, Anna Maria
/
Oulasvirta, Antti
Proceedings of DIS'14: Designing Interactive Systems
2014-06-21
v.1
p.1045-1054
© Copyright 2014 ACM
Summary: Inspired by the high keying rates of skilled pianists, we study the design
of piano keyboards for rapid text entry. We review the qualities of the piano
as an input device, observing four design opportunities: 1) chords, 2)
redundancy (more keys than letters in English), 3) the transfer of musical
skill and 4) optional sound feedback. Although some have been utilized in
previous text entry methods, our goal is to exploit all four in a single
design. We present PianoText, a computationally designed mapping that assigns
letter sequences of English to frequent note transitions of music. It allows
fast text entry on any MIDI-enabled keyboard and was evaluated in two
transcription typing studies. Both show an achievable rate of over 80 words per
minute. This parallels the rates of expert Qwerty typists and doubles that of a
previous piano-based design from the 19th century. We also design
PianoText-Mini, which allows for comparable performance in a portable form
factor. Informed by the studies, we estimate the upper bound of typing
performance, draw implications to other text entry methods, and critically
discuss outstanding design challenges.
PianoText: redesigning the piano keyboard for text entry
Demonstrations
/
Feit, Anna Maria
/
Oulasvirta, Antti
Companion Proceedings of DIS'14: Designing Interactive Systems
2014-06-21
v.2
p.129-132
© Copyright 2014 ACM
Summary: Inspired by the high keying rates of skilled pianists we study the design of
piano keyboards for rapid text entry. We present PianoText, a computationally
designed mapping that assigns letter sequences of English to frequent note
transitions in music. The design is based on four concepts: 1) redundancy, 2)
chords, 3) sound and 4) skill transfer. It allows fast text entry of over 80
wpm on any MIDI enabled keyboard. At the demonstration, visitors can explore
the benefits of these concepts by typing on PianoText -- Mini, a device that
allows for piano-based typing at a portable form factor.
Modeling the perception of user performance
User models and prediction
/
Nicosia, Max
/
Oulasvirta, Antti
/
Kristensson, Per Ola
Proceedings of ACM CHI 2014 Conference on Human Factors in Computing Systems
2014-04-26
v.1
p.1747-1756
© Copyright 2014 ACM
Summary: This paper studies how users perceive their own performance in two
alternative user interfaces. We extend methodology from psychophysics to the
study of interactive performance and conduct two experiments in order to create
a model of users' perception of their own performance. In our studies, two
interfaces are sequentially used in a pointing task, and users are asked to
rate in which interface their performance was higher. We first differentiate
the effects of objective performance (speed and accuracy) versus interface
qualities (distance between elements and width of elements) on perceived
performance. We then derive a model that predicts the amount of change required
in an interface for users to reliably detect a difference. The model is useful
as a heuristic for predicting if a new interface design is better enough for
users to reliably appreciate the obtained gain in user performance. We validate
the model via a separate user study, and conclude by discussing how to apply
our findings to design problems.
