Vassilis Kostakos

• PhD
• Professor at University of Melbourne

What mechanism links climate change and social change? Palaeoanthropological analysis of human remains suggests that abrupt climate change is linked to societal restructuring, but it has been challenging to reliably identify the exact mechanisms underlying this relationship. Here we identify one potential mechanism that can link climate to behavior...

We present a mobile instrumentation toolkit, AWARE, an open-source effort to develop an extensible and reusable platform for capturing, inferring, and generating context on mobile devices. Mobile phones are sensor-rich but resource-constrained, and therefore several considerations need to be addressed when creating a research tool that ensures prob...

This paper makes contributions toward adopting a systemic view of city-wide ubiquitous systems. Here, we present methods and techniques for combining multiple sensing modalities to measure and model traffic patterns in urban environments. We show how noise in one modality can be reduced by considering another more reliable modality and how two moda...

Background Digital assessment of behaviours, including physical activity, sleep, and social interactions could be associated with changes in mood and other mental health symptoms. This study assessed the safety, feasibility, acceptability, and potential predictive value of passive and active sensing in young people with major depressive disorder (M...

Purpose Physical activity could be associated with psychological symptoms in young people with major depressive disorder (MDD). Using actigraphy and ecological momentary assessment (EMA), we investigated the associations between physical activity and stress, anxiety and positive and negative affect in young people with MDD. Methods Actigraphy and...

Background Smartphones have become an indispensable part of people’s lives, and the fear of being without them, what has been termed “no mobile phone phobia” (nomophobia), is a growing phenomenon. The rise of problematic smartphone use highlights the urgent need to explore the intricate relationship between smartphones and human behavior. However,...

The ubiquity of smartphones offers a unique lens for studying human behavior in natural settings. Smartphone sensing, an expanding field driven by the widespread use of sensor-rich smartphones, facilitates observation and analysis of natural, “in-the-wild” behavior. These devices enable the seamless and unobtrusive collection of data across a broad...

The fog computing paradigm is rapidly gaining popularity for latency-critical and bandwidth-hungry IoT application deployment. Meanwhile, MicroService Architecture (MSA) is increasingly adopted for developing IoT applications due to its high scalability and extensibility. For mission-critical IoT services in fog, reliability remains one of the most...

Journaling offers significant benefits, including fostering self-reflection, enhancing writing skills, and aiding in mood monitoring. However, many people abandon the practice because traditional journaling is time-consuming, and detailed life events may be overlooked if not recorded promptly. Given that smartphones are the most widely used devices...

The proliferation of mobile sensing technologies has enabled the study of various physiological and behavioural phenomena through unobtrusive data collection from smartphone sensors. This approach offers real-time insights into individuals' physical and mental states, creating opportunities for personalised treatment and interventions. However, the...

This demo presents a novel end-to-end framework that combines on-device large language models (LLMs) with smartphone sensing technologies to achieve context-aware and personalized services. The framework addresses critical limitations of current personalization solutions via cloud-based LLMs, such as privacy concerns, latency and cost, and limited...

Smartphones have become essential to people's digital lives, providing a continuous stream of information and connectivity. However, this constant flow can lead to moments where users are simply passing time rather than engaging meaningfully. This underscores the importance of developing methods to identify these "time-killing" moments, enabling th...

Mobile near-infrared sensing is becoming an increasingly important method in many research and industrial areas. To help consolidate progress in this area, we use the PRISMA guidelines to conduct a systematic review of mobile near-infrared sensing, including 1) existing prototypes and commercial products; 2) data collection techniques; 3) machine l...

UNSTRUCTURED Smartphones have become an indispensable part of people’s lives, and the fear of being without them, what has been termed ‘nomophobia’, is a growing phenomenon. The connections among nomophobia, mental health measures, smartphone usage, and daily activities remains largely unexplored. This paper investigates nomophobia by analysing dat...

BACKGROUND Implantable Medical Devices (IMDs), such as pacemakers, increasingly communicate wirelessly with external devices. To secure this wireless communication channel, a pairing process is needed to bootstrap a secret key between the devices. Previous work has proposed pairing approaches that often adopt a “seamless” design and render the pair...

We present a fully-printable method to embed interactive information inside 3D printed objects. The information is invisible to the human eye and can be read using thermal imaging after temperature transfer through interaction with the objects. Prior methods either modify the surface appearance, require customized devices or not commonly used mater...

ChatGPT and other large language models (LLMs) have proven useful in crowdsourcing tasks, where they can effectively annotate machine learning training data. However, this means that they also have the potential for misuse, specifically to automatically answer surveys. LLMs can potentially circumvent quality assurance measures, thereby threatening...

Objectives: Hand hygiene has long been promoted as the most effective way to prevent the transmission of infection. However, due to the low compliance and quality of hand hygiene reported in previous studies, constant monitoring of healthcare workers' hand hygiene compliance and quality is crucial. In this study, we investigate the feasibility of...

The Fog computing paradigm utilises distributed, heterogeneous and resource-constrained devices at the edge of the network for efficient deployment of latency-critical and bandwidth-hungry IoT application services. Moreover, MicroService Architecture (MSA) is increasingly adopted to keep up with the rapid development and deployment needs of fast-ev...

MicroService Architecture (MSA) is gaining rapid popularity for developing large-scale IoT applications for deployment within distributed and resource-constrained Fog computing environments. As a cloud-native application architecture, the true power of microservices comes from their loosely coupled, independently deployable and scalable nature, ena...

Background: Young people are vulnerable to experiencing problematic levels of loneliness which can lead to poor mental health outcomes. Loneliness is a malleable treatment target and preliminary evidence has shown that it can be addressed with digital platforms. Peer Tree is a strength-based digital smartphone application aimed at reducing lonelin...

Artificial intelligence (AI) systems have been increasingly used to make decision-making processes faster, more accurate, and more efficient. However, such systems are also at constant risk of being attacked. While the majority of attacks targeting AI-based applications aim to manipulate classifiers or training data and alter the output of an AI mo...

The design and evaluation of accessibility technology is a core component of the computer science landscape, aiming to ensure that digital innovations are accessible to all. One of the most prominent and long-lasting areas of accessibility research focuses on motor impairments—deficiencies that affect the ability to move, manipulate objects, and in...

Artificial Intelligence (AI) systems have been increasingly used to make decision-making processes faster, more accurate, and more efficient. However, such systems are also at constant risk of being attacked. While the majority of attacks targeting AI-based applications aim to manipulate classifiers or training data and alter the output of an AI mo...

BACKGROUND Low engagement rates with digital mental health interventions are a major challenge in the field. Multicomponent digital interventions aim to improve engagement by adding components such as social networks. Although social networks may be engaging, they may not be sufficient to improve clinical outcomes or lead users to engage with key t...

Background Low engagement rates with digital mental health interventions are a major challenge in the field. Multicomponent digital interventions aim to improve engagement by adding components such as social networks. Although social networks may be engaging, they may not be sufficient to improve clinical outcomes or lead users to engage with key t...

Smart speakers have become exceedingly popular and entered many people's homes due to their ability to engage users with natural conversations. Researchers have also looked into using smart speakers as an interface to collect self-reported health data through conversations. Responding to surveys prompted by smart speakers requires users to listen t...

Due to their widespread adoption, frequent use, and diverse sensor capabilities, smartphones have become a powerful tool for academic studies focused on sampling human behaviour. While packing many technological advances, the need for researchers to develop their own software packages in order to run smartphone-based studies has resulted in a clear...

Emotion has long been acknowledged as an important part of technology user experience. More recently, research has begun to catalogue ways in which people use technology to manage and shape emotion. These have been characterised as emerging digital forms of a category of behaviour known to psychologists as emotion regulation. Since digital emotion...

Smartphone use has become an indispensable aspect of daily life for billions of people. Increasingly, researchers are examining the impact of smartphone use upon psychological well-being. However, little research has investigated how people deliberately use their smartphones to shape affective states; in other words, how smartphones are used as too...

Hand hygiene can reduce the transmission of pathogens and prevent healthcare-associated infections. Ultraviolet (UV) test is an effective tool for evaluating and visualizing hand hygiene quality during medical training. However, due to various hand shapes, sizes, and positions, systematic documentation of the UV test results to summarize frequently...

Edge and Fog computing paradigms utilise distributed, heterogeneous and resource-constrained devices at the edge of the network for efficient deployment of latency-critical and bandwidth-hungry IoT application services. Moreover, MicroService Architecture (MSA) is increasingly adopted to keep up with the rapid development and deployment needs of th...

The World Health Organization (WHO) recommends a six-step hand hygiene technique. Although multiple studies have reported that this technique yields inadequate skin coverage outcomes, they have relied on manual labeling that provided low-resolution estimations of skin coverage outcomes. We have developed a computational system to precisely quantify...

Non-invasive inspection and imaging techniques are used to acquire non-visible information embedded in samples. Typical applications include medical imaging, defect evaluation, and electronics testing. However, existing methods have specific limitations, including safety risks ( e.g. , X-ray), equipment costs ( e.g. , optical tomography), personnel...

Emotion has been studied in HCI for two decades, with specific traditions interested in sensing, expressing, transmitting, modelling, experiencing, visualizing, understanding, constructing, regulating, manipulating or adapting to emotion in human-human and human-computer interactions. This CHI 2022 workshop on the Future of Emotion in Human-Compute...

Technology plays an increasingly prominent role in emotional lives. Researchers have begun to study how people use devices to cope with and shape emotions: a phenomenon that has been called Digital Emotion Regulation. We report a study of the impact of the COVID-19 pandemic upon young people's digital habits and emotion regulation behaviors. We con...

Quality improvement methods are essential to gathering high-quality crowdsourced data, both for research and industry applications. A popular and broadly applicable method is task assignment that dynamically adjusts crowd workflow parameters. In this survey, we review task assignment methods that address: heterogeneous task assignment, question ass...

The Fog computing paradigm, offering cloud-like services at the edge of the network, has become a feasible model to support computing and storage capabilities required by latency-sensitive and bandwidth-hungry Internet of Things (IoT) applications. As fog devices are distributed, heterogeneous and resource-constrained, efficient application schedul...

Voice assistants, such as Amazon's Alexa and Google Home, increasingly find their way into consumer homes. Their functionality, however, is currently limited to being passive answer machines rather than proactively engaging users in conversations. Speakers' proactivity would open up a range of important application scenarios, including health servi...

We present UbiNIRS, a software framework for rapid development and deployment of applications using miniaturized near-infrared spectroscopy (NIRS). NIRS is an emerging material sensing technology that has shown a great potential in recent work from the HCI community such as in situ pill testing. However, existing methods require significant program...

We present a technique to embed information invisible to the eye inside 3D printed objects. The information is integrated in the object model, and then fabricated using off-the-shelf dual-head FDM (Fused Deposition Modeling) 3D printers. Our process does not require human intervention during or after printing with the integrated model. The informat...

Quality improvement methods are essential to gathering high-quality crowdsourced data, both for research and industry applications. A popular and broadly applicable method is task assignment that dynamically adjusts crowd workflow parameters. In this survey, we review task assignment methods that address: heterogeneous task assignment, question ass...

Social conformity is the act of individuals adjusting their personal opinions to agree with an opposing majority. Previous work has identified multiple determinants of social conformity in controlled laboratory studies, but they remain largely untested in naturalistic online environments. For this study, we developed a realistic debating website, w...

The global pandemic and the uncertainty if and when life will return to normality have motivated a series of studies on human mental health. This research has elicited evidence for increasing numbers of anxiety, depression, and overall impaired mental well-being. But, the global COVID-19 pandemic has also created new opportunities for research into...

Emotions have a significant impact on our decision-making, learning, awareness, social interactions, and mental and physical health. Even though large efforts have been put into quantifying human emotions, their subjectivity, context-dependence, and complexity render them as being almost unpredictable. However, while different streams of research i...

Social conformity is the act of individuals adjusting personal judgements to conform to expectations of opposing majorities in group settings. While conformity has been studied in online groups with emphasis on its contextual determinants (e.g., group size, social presence, task objectivity), the effect of age – of both the individual and the membe...

Background Although convenient and reliable modern messaging apps like WhatsApp enable efficient communication among hospital staff, hospitals are now pivoting toward purpose-built structured communication apps for various reasons, including security and privacy concerns. However, there is limited understanding of how we can examine and improve hos...

Crowdsourced labor markets represent a powerful new paradigm for accomplishing work. Understanding the motivating factors that lead to high quality work could have significant benefits. However, researchers have so far found that motivating factors such as increased monetary reward generally increase workers’ willingness to accept a task or the spe...

The Experience Sampling Method is used to collect participant self-reports over extended observation periods. These self-reports offer a rich insight into the individual lives of study participants by intermittently asking participants a set of questions. However, the longitudinal and repetitive nature of this sampling approach introduces a variety...

Background: Young people are vulnerable to experiencing problematic levels of loneliness which can lead to poor mental health outcomes. Loneliness is a malleable treatment target and preliminary evidence has shown that it can be addressed with digital platforms. Peer Tree is a strengths-based digital smartphone application aimed at reducing lonelin...

Despite large investments in smartwatch development, the market growth remains smaller than forecasted. The purpose of smartwatch use remains unclear, indicated by the lack of large-scale adoption. Thus, we aim to better understand the early adoption and everyday smartwatch use. We investigate a diverse usage data of smartwatches logged over a peri...

With the wide expansion of distributed learning environments the way we learn became more diverse than ever. This poses an opportunity to incorporate different data sources of learning traces that can offer broader insights into learner behavior and the intricacies of the learning process. We argue that combining analytics across different e-learni...

In this paper, we investigate the feasibility of using mobility patterns and demographic data to predict hospital visits. We collect mobility traces from two thousand users for around two months. We extract 16 mobility features from these passively collected mobility traces and train an XGBoost model to predict users' hospital visits. We demonstrat...

BACKGROUND Although convenient and reliable modern messaging apps like WhatsApp enable efficient communication among hospital staff, hospitals are now pivoting toward purpose-built structured communication apps for various reasons, including security and privacy concerns. However, there is limited understanding of how we can examine and improve hos...

Background: Hand hygiene is one of the most effective ways of preventing health care–associated infections and reducing their transmission. Owing to recent advances in sensing technologies, electronic hand hygiene monitoring systems have been integrated into the daily routines of health care workers to measure their hand hygiene compliance and qual...

BACKGROUND Hand hygiene is one of the most effective ways of preventing health care–associated infections and reducing their transmission. Owing to recent advances in sensing technologies, electronic hand hygiene monitoring systems have been integrated into the daily routines of health care workers to measure their hand hygiene compliance and quali...

In the context of learning systems, identifying causal relationships among information presented to the user, their behavior and cognitive effort required/exerted to understand and perform a task is key to building effective learning experiences, and to maintain engagement in learning processes. An unexplored question is whether our interaction wit...

NIRS is a spectroscopic method that propagates near-infrared waves through objects and measures the absorbance by diffuse reflection, users could analyze the composition information of objects based on that. The technology has fast speed and non-destructive analysis features with relatively simple requirements for operators, making it very friendly...

Background The use of location-based data in clinical settings is often limited to real-time monitoring. In this study, we aim to develop a proximity-based localization system and show how its longitudinal deployment can provide operational insights related to staff and patients' mobility and room occupancy in clinical settings. Such a streamlined...

While crowd workers typically complete a variety of tasks in crowdsourcing platforms, there is no widely accepted method to successfully match workers to different types of tasks. Researchers have considered using worker demographics, behavioural traces, and prior task completion records to optimise task assignment. However, optimum task assignment...

Although crowd work is typically completed through desktop or laptop computers by workers at their home, literature has shown that crowdsourcing is feasible through a wide array of computing devices, including smartphones and digital voice assistants. An integrated crowdsourcing platform that operates across multiple devices could provide greater f...

A catalyst for the spread of fake news is the existence of comments that users make in support of, or against, such articles. In this study we investigate whether critical and supportive comments can induce conformity in how readers perceive trustworthiness of news articles and respond to them. We find that individuals tend to conform to the majori...

Recent years have witnessed much work unraveling human mobility patterns through urban visitation and location check-in data. Traditionally, user visitation and check-in have been assumed as the same behavior, yet this fundamental assumption can be questionable and lacks supporting evidence. In this paper, we seek to understand the similarities and...

Although crowd work is typically completed through desktop or laptop computers by workers at their home, literature has shown that crowdsourcing is feasible through a wide array of computing devices, including smartphones and digital voice assistants. An integrated crowdsourcing platform that operates across multiple devices could provide greater f...

Sensing and machine learning advances have enabled the unobtrusive measurement of physiological responses and facial expressions so as to estimate one's cognitive performance. This often boils down to mapping the states of the cognitive processes underpinning human cognition: physiological responses (e.g., heart rate) and facial expressions (e.g.,...

The articles in this special section focus on personalized pervasive health. For over more than two decades, mobile, wearable, and ambient sensor and interaction devices have grown into today’s plethora of computing platforms and tools for pervasive health. Pervasive computing is now assimilating into medicine, from disease risk prevention to diagn...

Kinship verification is the problem whereby a third party determines whether two people are related. Despite previous research in Psychology and Machine Vision, the factors affecting a person's verification ability are poorly understood. Through an online crowdsourcing study, we investigate the impact of gender, race and medium type (image vs video...

Physical, mental, and behavioral processes of most living beings underlie cyclic changes, mainly governed by the day-night cycle. Investigations of these circadian rhythms have traditionally required constrained settings and invasive methods, such as repetitive blood testing and testing in sleep laboratories. Recent developments in pervasive techno...

Social conformity occurs when individuals in group settings change their personal opinion to be in agreement with the majority's position. While recent literature frequently reports on conformity in online group settings, the causes for online conformity are yet to be fully understood. This study aims to understand how social presencei.e., the sens...

BACKGROUND The use of location-based data in clinical settings is often limited to real-time monitoring. Here we develop a proximity-based localisation system, and show how its longitudinal analysis can provide operational insights relating to mobility and occupancy in clinical settings. OBJECTIVE We measure the accuracy of the system, and algorit...

Inspired by the increasing prevalence of digital voice assistants, we demonstrate the feasibility of using voice interfaces to deploy and complete crowd tasks. We have developed Crowd Tasker, a novel system that delivers crowd tasks through a digital voice assistant. In a lab study, we validate our proof-of-concept and show that crowd task performa...

Purpose The purpose of this paper is to propose a distributed smartphone sensing-enabled system, which assumes an intelligent transport signaling (ITS) infrastructure that operates traffic lights in a smart city (SC). The system is able to handle priorities between groups of cyclists (crowd-cycling) and traffic when approaching traffic lights at ro...

Equipped with an abundance of small-scale microelectromechanical sensors, modern mobile devices such as smartphones and smartwatches can now offer context-aware services to users in mobile environments. Although advances in mobile context-aware applications have made our everyday environments increasingly intelligent, these applications are prone t...

Despite decades of research concerning social conformity and its effects on face-to-face groups, it is yet to be comprehensively investigated in online contexts. In our work, we investigate the impact of contextual determinants (such as majority group size, the number of opposing minorities and their sizes, and the nature of the task) and personal...

Researchers in Human-Computer Interaction typically rely on experiments to assess the causal effects of experimental conditions on variables of interest. Although this classic approach can be very useful, it offers little help in tackling questions of causality in the kind of data that are increasingly common in HCI – capturing user behavior ‘in th...

The articles in this special section explore the use of pervasive technology by and for children and teens. A number of pervasive computing products and services are now available for play, education, learning, and smart living. It is, therefore, important to understand how they affect—and how they are used by—children and teens who are growing up...