We are happy to present you this year’s contributions from the German HCI labs to CHI 2021! Feel free to browse our list of publications: There are 53 full papers (including one Best Paper and five Honorable Mentions), 16 LBWs, and many demonstrations, workshops, or other interesting publications. Please send us a mail if you feel that your paper is missing or to correct any entries.
Artificially Intelligent Technology for the Margins: A Multidisciplinary Design Agenda
Franziska Tachtler (TU Wien), Konstantin Aal (University of Siegen), Tanja Ertl (University of Siegen), Daniel Diethei (University of Bremen), Jasmin Niess (University of Bremen), Mohammed Khwaja (Imperial College London), Reem Talhouk (Northumbria University), Giovanna Nunes Vilaza (Technical University of Denmark), Shaimaa Lazem (City of Scientific Research, Technological Applications), Aneesha Singh (University College London), Marguerite Barry (University College Dublin), Volker Wulf (University of Siegen), Geraldine Fitzpatrick (TU Wien)
Abstract | Tags: Workshop | Links:
@inproceedings{Tachtler2021chiworkshop,
title = {Artificially Intelligent Technology for the Margins: A Multidisciplinary Design Agenda},
author = {Franziska Tachtler (TU Wien), Konstantin Aal (University of Siegen), Tanja Ertl (University of Siegen), Daniel Diethei (University of Bremen), Jasmin Niess (University of Bremen), Mohammed Khwaja (Imperial College London), Reem Talhouk (Northumbria University), Giovanna Nunes Vilaza (Technical University of Denmark), Shaimaa Lazem (City of Scientific Research and Technological Applications), Aneesha Singh (University College London), Marguerite Barry (University College Dublin), Volker Wulf (University of Siegen), Geraldine Fitzpatrick (TU Wien)},
url = {http://wineme.uni-siegen.de/, Information Systems and New Media University of Siegen},
doi = {10.1145/3411763.3441333},
year = {2021},
date = {2021-05-01},
abstract = {There has been increasing interest in socially just use of Artificial Intelligence (AI) and Machine Learning (ML) in the development of technology that may be extended to marginalized people. However, the exploration of such technologies entails the development of an understanding of how they may increase and/or counter marginalization. The use of AI/ML algorithms can lead to several challenges, such as privacy and security concerns, biases, unfairness, and lack of cultural awareness, which especially affect marginalized people. This workshop will provide a forum to share experiences and challenges of developing AI/ML health and social wellbeing technologies with/for marginalized people and will work towards developing design methods to engage in the re-envisioning of AI/ML technologies for and with marginalized people. In doing so we will create cross-research area dialogues and collaborations. These discussions build a basis to (1) explore potential tools to support designing AI/ML systems with marginalized people, and (2) develop a design agenda for future research and AI/ML technology for and with marginalized people.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
There has been increasing interest in socially just use of Artificial Intelligence (AI) and Machine Learning (ML) in the development of technology that may be extended to marginalized people. However, the exploration of such technologies entails the development of an understanding of how they may increase and/or counter marginalization. The use of AI/ML algorithms can lead to several challenges, such as privacy and security concerns, biases, unfairness, and lack of cultural awareness, which especially affect marginalized people. This workshop will provide a forum to share experiences and challenges of developing AI/ML health and social wellbeing technologies with/for marginalized people and will work towards developing design methods to engage in the re-envisioning of AI/ML technologies for and with marginalized people. In doing so we will create cross-research area dialogues and collaborations. These discussions build a basis to (1) explore potential tools to support designing AI/ML systems with marginalized people, and (2) develop a design agenda for future research and AI/ML technology for and with marginalized people.
Coping with Messiness in Ethnography: Authority, Bias and Immersion in ethnographic Fieldwork in the non-Western World
Marios Mouratidis (University of Siegen), Sarah Rüller (University of Siegen), Konstantin Aal (University of Siegen), Nina Boulus-Rødje (Roskilde University), Shaimaa Lazem (City of Scientifc Research, Technological Applications), Anicia Peters (Namibia University of Science, Technology), Simon Holdermann (University of Cologne), Vasilis Vlachokyriakos (Newcastle University), Ann Light (University of Sussex), Dave Randall (University of Siegen), Volker Wulf (University of Siegen)
Abstract | Tags: Workshop | Links:
@inproceedings{Mouratidis2021ethnography,
title = {Coping with Messiness in Ethnography: Authority, Bias and Immersion in ethnographic Fieldwork in the non-Western World},
author = {Marios Mouratidis (University of Siegen) and Sarah Rüller (University of Siegen) and Konstantin Aal (University of Siegen) and Nina Boulus-Rødje (Roskilde University) and Shaimaa Lazem (City of Scientifc Research, Technological Applications) and Anicia Peters (Namibia University of Science and Technology), Simon Holdermann (University of Cologne) and Vasilis Vlachokyriakos (Newcastle University) and Ann Light (University of Sussex) and Dave Randall (University of Siegen) and Volker Wulf (University of Siegen)},
url = {https://www.wineme.uni-siegen.de/ (lab page)},
doi = {10.1145/3411763.3441328},
year = {2021},
date = {2021-05-07},
abstract = {Ethnography has frmly established its position in the Human-Computer Interaction (HCI) community. Many studies have benefted from following ethnographic approaches to arrive at a grounded and comprehensive understanding of the respective research context. Applying that to the non-Western world, however, comes with challenges for researchers. Aside from ethical concerns which have been addressed in the past, we want to use this workshop to foster conversations and discussions on authority, bias and immersion when conducting ethnographic feld work in the non-Western world – especially as a Western researcher. The main objective of this workshop is to exchange experiences and to identify common aspects and ways of overcoming, coping with or even embracing the messiness in ethnographic work and derive guidelines based on these discussions.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
Ethnography has frmly established its position in the Human-Computer Interaction (HCI) community. Many studies have benefted from following ethnographic approaches to arrive at a grounded and comprehensive understanding of the respective research context. Applying that to the non-Western world, however, comes with challenges for researchers. Aside from ethical concerns which have been addressed in the past, we want to use this workshop to foster conversations and discussions on authority, bias and immersion when conducting ethnographic feld work in the non-Western world – especially as a Western researcher. The main objective of this workshop is to exchange experiences and to identify common aspects and ways of overcoming, coping with or even embracing the messiness in ethnographic work and derive guidelines based on these discussions.
Cycling@CHI: Towards a Research Agenda for HCI in the Bike Lane
Gian-Luca Savino (University of Bremen), Tamara von Sawitzky (Technische Hochschule Ingolstadt), Andrii Matviienko (Technical University of Darmstadt), Miriam Sturdee (Lancaster University), Paweł W. Woźniak (Utrecht University), Markus Löchtefeld (Aalborg University), Andrew L. Kun (University of New Hampshire), Andreas Riener (Technische Hochschule Ingolstadt), Jonna Häkkilä (University of Lapland)
Abstract | Tags: Workshop | Links:
@workshop{2021SavinoCycling,
title = {Cycling@CHI: Towards a Research Agenda for HCI in the Bike Lane},
author = {Gian-Luca Savino (University of Bremen) and Tamara von Sawitzky (Technische Hochschule Ingolstadt) and Andrii Matviienko (Technical University of Darmstadt) and Miriam Sturdee (Lancaster University) and Paweł W. Woźniak (Utrecht University) and Markus Löchtefeld (Aalborg University) and Andrew L. Kun (University of New Hampshire) and Andreas Riener (Technische Hochschule Ingolstadt) and Jonna Häkkilä (University of Lapland)},
url = {https://hci.uni-bremen.de/, Website - HCI University of Bremen
https://twitter.com/HCIBremen, Twitter - HCI University of Bremen
},
doi = {10.1145/3411763.3441316},
year = {2021},
date = {2021-05-01},
abstract = {In this workshop, we will explore and discuss future developments in mobile user-interfaces for cyclists and users of similar interfaces or services. We highlight the challenge of balancing safety and ecological validity in experiments, and how novel and improved evaluation methods can improve the current situation. We aim to bring together researchers with a strong background in designing and evaluating novel user interfaces in the domain of bicycles and mobility, as well as practitioners who build consumer products in that domain. The workshop's goal is to explore novel ways of designing and evaluating user interfaces for cyclists and similar users when it comes to interacting with mobile devices and services on the ride.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {workshop}
}
In this workshop, we will explore and discuss future developments in mobile user-interfaces for cyclists and users of similar interfaces or services. We highlight the challenge of balancing safety and ecological validity in experiments, and how novel and improved evaluation methods can improve the current situation. We aim to bring together researchers with a strong background in designing and evaluating novel user interfaces in the domain of bicycles and mobility, as well as practitioners who build consumer products in that domain. The workshop's goal is to explore novel ways of designing and evaluating user interfaces for cyclists and similar users when it comes to interacting with mobile devices and services on the ride.
Decolonizing HCI Across Borders
Vikram Kamath Cannanure (Carnegie Mellon University), Dilrukshi Gamage (University of Moratuwa), Christian Sturm (Hamm-Lippstadt University of Applied Sciences), Heike Winschiers-Theophilus (Namibia University of Science, Technology), F. Maestre (Indiana University Bloomington), Naveena Karusala (University of Washington), Pedro Reynolds-Cuéllar (MIT), Neha Kumar (Georgia Tech)
Abstract | Tags: Workshop | Links:
@inproceedings{Cannanure2021Across,
title = {Decolonizing HCI Across Borders},
author = {Vikram Kamath Cannanure (Carnegie Mellon University) and Dilrukshi Gamage (University of Moratuwa) and Christian Sturm (Hamm-Lippstadt University of Applied Sciences) and Heike Winschiers-Theophilus (Namibia University of Science and Technology) and F. Maestre (Indiana University Bloomington) and Naveena Karusala (University of Washington) and Pedro Reynolds-Cuéllar (MIT) and Neha Kumar (Georgia Tech)},
doi = {10.1145/3411763.3441348},
year = {2021},
date = {2021-05-07},
abstract = {The HCI Across Borders (HCIxB) community has been growing in recent years, starting with the Development Consortium at CHI 2016 and the HCIxB Symposia at CHI 2017, 2018, and 2019. This year, we propose an HCIxB symposium that continues to foster scholarship potential of early-career HCIxB researchers across the world, particularly those from and in the Global South, engaging on the topic of decoloniality. Through this symposium, we aim to create the space for discussions that have been emerging in pockets of the HCI community but could benefit from greater attention in the interest of demarginalizing members and research areas of the community that have thus far been on the margins of HCI. We expect this virtual workshop at CHI 2021 to be the inaugural session for a series of virtual events to continue this conversation on decolonizing HCI's borders into individual subgroups.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
The HCI Across Borders (HCIxB) community has been growing in recent years, starting with the Development Consortium at CHI 2016 and the HCIxB Symposia at CHI 2017, 2018, and 2019. This year, we propose an HCIxB symposium that continues to foster scholarship potential of early-career HCIxB researchers across the world, particularly those from and in the Global South, engaging on the topic of decoloniality. Through this symposium, we aim to create the space for discussions that have been emerging in pockets of the HCI community but could benefit from greater attention in the interest of demarginalizing members and research areas of the community that have thus far been on the margins of HCI. We expect this virtual workshop at CHI 2021 to be the inaugural session for a series of virtual events to continue this conversation on decolonizing HCI's borders into individual subgroups.
Designing for New Forms of Vulnerability: Exploring transformation and empowerment in times of COVID-19
David Struzek (University of Siegen, Information Systems/IT for the ageing society, Germany), Katerina Cerna University of Siegen, Information Systems/IT for the ageing society, Germany), Richard Paluch University of Siegen, Information Systems/IT for the ageing society, Germany), Sven Bittenbinder University of Siegen, Information Systems/IT for the ageing society, Germany), Claudia Müller (University of Siegen, Information Systems/IT for the ageing society, Germany), Arlind Reuter (Open Lab, Newcastle University, United Kingdom), Lydia Stamato (Department of Information Systems at the University of Maryland, Baltimore County, United States), Özge Subasi (College of Social Sciences, Humanities at Koc University, Turkey), Foad Hamidi (Department of Information Systems at the University of Maryland, Baltimore County, United States), John Vines (University of Edinburgh, United Kingdom)
Abstract | Tags: Workshop | Links:
@inproceedings{Struzek2021Vulnerability,
title = {Designing for New Forms of Vulnerability: Exploring transformation and empowerment in times of COVID-19},
author = {David Struzek (University of Siegen, Information Systems/IT for the ageing society, Germany) and Katerina Cerna University of Siegen, Information Systems/IT for the ageing society, Germany) and Richard Paluch University of Siegen, Information Systems/IT for the ageing society, Germany) and Sven Bittenbinder University of Siegen, Information Systems/IT for the ageing society, Germany), Claudia Müller (University of Siegen, Information Systems/IT for the ageing society, Germany) and Arlind Reuter (Open Lab, Newcastle University, United Kingdom) and Lydia Stamato (Department of Information Systems at the University of Maryland, Baltimore County, United States) and Özge Subasi (College of Social Sciences and Humanities at Koc University, Turkey), Foad Hamidi (Department of Information Systems at the University of Maryland, Baltimore County, United States) and John Vines (University of Edinburgh, United Kingdom)},
url = {https://italg.wineme.uni-siegen.de/ (lab page)},
doi = {10.1145/3411763.3441339},
year = {2021},
date = {2021-05-07},
abstract = {Our workshop will concentrate on vulnerability of specific social groups due to various reasons, including COVID-19, and the potential for technology design to result in empowerment. We want to address issues of what new forms of vulnerabilities emerge and how we can design digital environments in a way that acknowledges vulnerability but also has the potential to empower people in ways that are meaningful for them. When planning the workshop, we will also reflect on social situations that can result in vulnerabilities for participants. Therefore, we will ensure that interested participants will experience low barriers to participation include a variety of people with different backgrounds and ensure that interaction happens based on equality principles and in an atmosphere of solidarity. Participants can exchange ideas and thoughts without worrying about being exposed to biased assumptions. The workshop will allow for non-hierarchical and cooperative discussion and collaboration through interactive online exercises, resulting in a collaboratively developed zine. Finally, the social sustainability of the workshop will be ensured through a website, mailing lists, joint publications and continuous contact.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
Our workshop will concentrate on vulnerability of specific social groups due to various reasons, including COVID-19, and the potential for technology design to result in empowerment. We want to address issues of what new forms of vulnerabilities emerge and how we can design digital environments in a way that acknowledges vulnerability but also has the potential to empower people in ways that are meaningful for them. When planning the workshop, we will also reflect on social situations that can result in vulnerabilities for participants. Therefore, we will ensure that interested participants will experience low barriers to participation include a variety of people with different backgrounds and ensure that interaction happens based on equality principles and in an atmosphere of solidarity. Participants can exchange ideas and thoughts without worrying about being exposed to biased assumptions. The workshop will allow for non-hierarchical and cooperative discussion and collaboration through interactive online exercises, resulting in a collaboratively developed zine. Finally, the social sustainability of the workshop will be ensured through a website, mailing lists, joint publications and continuous contact.
Evaluating User Experiences in Mixed Reality
Dmitry Alexandrovsky (University of Bremen, Digital Media Lab), Susanne Putze (University of Bremen, Digital Media Lab), Valentin Schwind (Frankfurt University of Applied Sciences), Elisa D Mekler (Aalto University), Jan David Smeddinck (Newcastle University), Denise Kahl (German Research Center for Artificial Intelligence (DFKI), Saarland Informatics Campus), Antonio Krüger (DFKI, Saarland Informatics Campus), Rainer Malaka (University of Bremen, Digital Media Lab)
Abstract | Tags: Workshop | Links:
@inproceedings{2021AlexandrovskyEvaluating,
title = {Evaluating User Experiences in Mixed Reality},
author = {Dmitry Alexandrovsky (University of Bremen, Digital Media Lab) and Susanne Putze (University of Bremen, Digital Media Lab) and Valentin Schwind (Frankfurt University of Applied Sciences) and Elisa D Mekler (Aalto University) and Jan David Smeddinck (Newcastle University) and Denise Kahl (German Research Center for Artificial Intelligence (DFKI), Saarland Informatics Campus) and Antonio Krüger (DFKI, Saarland Informatics Campus) and Rainer Malaka (University of Bremen, Digital Media Lab)},
url = {http://dm.tzi.de/, Website - Digital Media Lab
https://twitter.com/dmlabbremen, Twitter - Digital Media Lab
https://sputze.github.io/evaluating-mr/, Workshop Website},
doi = {10.1145/3411763.3441337},
year = {2021},
date = {2021-05-07},
abstract = {Measuring user experience in MR (i.e., AR/VR) user studies is essential. Researchers apply a wide range of measuring methods using objective (e.g., biosignals, time logging), behavioral (e.g., gaze direction, movement amplitude), and subjective (e.g., standardized questionnaires) metrics. Many of these measurement instruments were adapted from use-cases outside ofvMR, but have not been validated for usage in MR experiments. However, researchers are faced with various challenges and design alternatives when measuring immersive experiences. These challenges become even more diverse when running out-of-the lab studies. Measurement methods of VR experience received recently much attention. For example, research has started embedding questionnaires in the VE for various applications, as this allows users to stay closer to the ongoing experience while filling out the survey. However, there is a diversity in the interaction methods and practices on how the assessment procedure is conducted. This diversity in methods underlines a missing shared agreement of standardized measurement tools for VR experiences. AR research strongly orients on the research methods from VR, e.g., using the same type of subjective questionnaires. However, there are some crucial technical differences that require deliberate considerations during the evaluation. This workshop at CHI 2021 provides a foundation to exchange expertise and to address challenges as well as opportunities of research methods in MR user studies. By this, our workshop launches a discussion of research methods that should lead to standardizing assessment methods in MR user studies. The outcomes of the workshop will be aggregated into a collective special issue journal article.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
Measuring user experience in MR (i.e., AR/VR) user studies is essential. Researchers apply a wide range of measuring methods using objective (e.g., biosignals, time logging), behavioral (e.g., gaze direction, movement amplitude), and subjective (e.g., standardized questionnaires) metrics. Many of these measurement instruments were adapted from use-cases outside ofvMR, but have not been validated for usage in MR experiments. However, researchers are faced with various challenges and design alternatives when measuring immersive experiences. These challenges become even more diverse when running out-of-the lab studies. Measurement methods of VR experience received recently much attention. For example, research has started embedding questionnaires in the VE for various applications, as this allows users to stay closer to the ongoing experience while filling out the survey. However, there is a diversity in the interaction methods and practices on how the assessment procedure is conducted. This diversity in methods underlines a missing shared agreement of standardized measurement tools for VR experiences. AR research strongly orients on the research methods from VR, e.g., using the same type of subjective questionnaires. However, there are some crucial technical differences that require deliberate considerations during the evaluation. This workshop at CHI 2021 provides a foundation to exchange expertise and to address challenges as well as opportunities of research methods in MR user studies. By this, our workshop launches a discussion of research methods that should lead to standardizing assessment methods in MR user studies. The outcomes of the workshop will be aggregated into a collective special issue journal article.
Everyday Proxy Objects for Virtual Reality
Florian Daiber (DFKI), Donald Degraen (DFKI), André Zenner (DFKI), Tanja Döring (University of Bremen), Frank Steinicke (Universität Hamburg), Oscar Javier Ariza Núñez (Universität Hamburg), Adalberto L. Simeone (KU Leuven)
Abstract | Tags: Workshop | Links:
@inproceedings{2021DaiberEveryday,
title = {Everyday Proxy Objects for Virtual Reality},
author = {Florian Daiber (DFKI) and Donald Degraen (DFKI) and André Zenner (DFKI) and Tanja Döring (University of Bremen) and Frank Steinicke (Universität Hamburg) and Oscar Javier Ariza Núñez (Universität Hamburg) and Adalberto L. Simeone (KU Leuven)},
url = {https://umtl.cs.uni-saarland.de/, Website - Ubiquitous Media Technology Lab
https://twitter.com/umtl, Twitter - Ubiquitous Media Technology Lab
http://epo4vr.dfki.de/, Workshop Website},
doi = {10.1145/3411763.3441343},
year = {2021},
date = {2021-05-01},
abstract = {Immersive virtual experiences are becoming ubiquitous in our daily lives. Besides visual and auditory feedback, other senses like haptics, smell and taste can enhance immersion in virtual environments. Most solutions presented in the past require specialized hardware to provide appropriate feedback. To mitigate this need, researchers conceptualized approaches leveraging everyday physical objects as proxies instead. Transferring these approaches to varying physical environments and conditions, however, poses significant challenges to a variety of disciplines such as HCI, VR, haptics, tracking, perceptual science, design, etc. This workshop will explore the integration of everyday items for multi-sensory feedback in virtual experiences and sets course for respective future research endeavors. Since the community still seems to lack a cohesive agenda for advancing this domain, the goal of this workshop is to bring together individuals interested in everyday proxy objects to review past work, build a unifying research agenda, share ongoing work, and encourage collaboration.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
Immersive virtual experiences are becoming ubiquitous in our daily lives. Besides visual and auditory feedback, other senses like haptics, smell and taste can enhance immersion in virtual environments. Most solutions presented in the past require specialized hardware to provide appropriate feedback. To mitigate this need, researchers conceptualized approaches leveraging everyday physical objects as proxies instead. Transferring these approaches to varying physical environments and conditions, however, poses significant challenges to a variety of disciplines such as HCI, VR, haptics, tracking, perceptual science, design, etc. This workshop will explore the integration of everyday items for multi-sensory feedback in virtual experiences and sets course for respective future research endeavors. Since the community still seems to lack a cohesive agenda for advancing this domain, the goal of this workshop is to bring together individuals interested in everyday proxy objects to review past work, build a unifying research agenda, share ongoing work, and encourage collaboration.
Out of Your Mind!? Embodied Interaction in Sports
Vincent van Rheden (University of Salzburg), Thomas Grah (University of Salzburg), Alexander Meschtscherjakov (University of Salzburg), Rakesh Patibanda (Monash University), Wanyu Liu (IRCAM Centre Pompidou), Florian Daiber (DFKI, Saarland Informatics Campus), Elise van den Hoven (University of Technology Sydney, Eindhoven University of Technology), Florian Floyd Mueller (Monash University)
Abstract | Tags: Workshop | Links:
@inproceedings{2021RhedenMind,
title = {Out of Your Mind!? Embodied Interaction in Sports},
author = {Vincent van Rheden (University of Salzburg) and Thomas Grah (University of Salzburg) and Alexander Meschtscherjakov (University of Salzburg) and Rakesh Patibanda (Monash University) and Wanyu Liu (IRCAM Centre Pompidou) and Florian Daiber (DFKI, Saarland Informatics Campus) and Elise van den Hoven (University of Technology Sydney, Eindhoven University of Technology) and Florian Floyd Mueller (Monash University)},
url = {https://umtl.cs.uni-saarland.de, Website - UMTLab
https://www.facebook.com/UMTLab/, Facebook - UMTLab
https://sports-hci.com/, Workshop Website},
doi = {10.1145/3411763.3441329},
year = {2021},
date = {2021-05-07},
abstract = {People engage in sportive activities for reasons beyond improving their athletic performance. They also seek experiences like fun, adventure, a feeling of oneness, clear their heads, and flow. Since sport is a highly bodily experience, we argue that taking an embodied interaction perspective to inspire interaction design of sports systems is a promising direction in HCI research and practice. This workshop will address the challenges of designing interactive systems in the realm of sports from an embodied interaction perspective focusing on athletes' experience rather than performance. We will explore how interactive systems enhance sports experience without distracting from the actual goal of the athlete, such as freeing the mind. We will focus on several topics of interest such as sensory augmentation, augmented experience, multi-modal interaction, and motor learning in sports.},
keywords = {Workshop},
pubstate = {published},
tppubtype = {inproceedings}
}
People engage in sportive activities for reasons beyond improving their athletic performance. They also seek experiences like fun, adventure, a feeling of oneness, clear their heads, and flow. Since sport is a highly bodily experience, we argue that taking an embodied interaction perspective to inspire interaction design of sports systems is a promising direction in HCI research and practice. This workshop will address the challenges of designing interactive systems in the realm of sports from an embodied interaction perspective focusing on athletes' experience rather than performance. We will explore how interactive systems enhance sports experience without distracting from the actual goal of the athlete, such as freeing the mind. We will focus on several topics of interest such as sensory augmentation, augmented experience, multi-modal interaction, and motor learning in sports.