In contemporary society, we are surrounded by not only physical materials, but also images of them. We are capable of judging materials and their properties with only visual information. For instance, if an object looks solid and glossy or soft and fluffy. This ability is called material perception. As for images, there are various ways of image making, such as photography, painting, computer rendering, etc. And a new method has emerged recently: generative AI. All these image generation methods can produce different appearances of the same object or material. In this thesis, we studied human visual perception of two types of appearances: appearance as material property, appearance as pictorial style and the interaction between them.

In Chapter 2, we investigated depiction style by zooming in on a single motif, an apple. By using the fragments instead of the whole painting, we were able to keep the subject matter relatively constant, and isolate style from composition as well as other contextual information. We first constructed a perceptual space of style using similarity judgements from online participants. Then we fitted perceived attributes to this space to understand its dimensions. The data resulted in a three-dimensional space. Dimension 1 is associated with smoothness and brushstroke coarseness. Dimensions 2 and 3 are related to hue and chroma. Surprisingly, we also found a rotational relation between creation year and the first two dimensions, revealing a certain cyclic, repetitive pattern of style. The results suggest style can already be perceived in fragments of paintings.

In Chapter 3, we studied the influence of medium on appearance. For example, imagine an oil-painted apple and a pencil-sketched apple: they can have different appearances. The comparison between different media has rarely been studied. One possible reason is the difficulty to isolate medium from its confounding factor, subject matter. We found a solution by comparing oil paintings and their engraved reproductions. The identical content gave us a perfect opportunity to compare material perception from two distinct media. We collected 15 pairs, consisting of 88 fragments depicting different materials like fabric, skin, wood and metal. We also created three manipulations to understand the effect of color (a grayscale version) and contrast (equalized histograms towards both painting and engraving). We collected ratings on five attributes: three-dimensionality, glossiness, convincingness, smoothness and softness. Paintings showed a broader perceived range than engravings, with contrast equalization having a greater impact on perception than color removal. Possibly engravers used local contrast to compensate the absence of color.

In Chapter 4, we analyzed an emerging medium from a non-human creator, generative AI. In two experiments, we explored human material perception using generative AI stimuli and compared the perceptual spaces of three generative AI models, as well as a computer-generated BRDF stimulus set, the MERL dataset. In Experiment 1, we used text descriptions of 32 materials from MERL (e.g. ‘green fabric’) as prompts for DALL-E 2 and Midjourney v2. Both AI models resulted in a 2D space while MERL resulted in a 1D one. The three spaces showed low similarity, suggesting the AI models generated unique and different images of materials from identical text prompts. In Experiment 2, we explored another text-to-image model Stable Diffusion v1.5 with an add-on, ControlNet. ControlNet allowed us to add additional graphical constraints besides text input. In this way we could inspect more complex shapes. We kept the same 32 descriptions and generated material blobs in three shapes, from simple to more complex geometry. The three perceptual spaces from the three shapes showed high similarity, indicating both robust structure and minor influence of object shape on material perception. Interestingly, the perceptual spaces from Experiment 2 also shared similar structure as perceptual spaces from other material studies using real-world photos, computer renderings and depictions. In sum, we investigated visual perception through the lens of art by examining appearances rendered by painters, engravers and generative AIs.

Nowadays, co-design is progressively popular in the area of customized retail services. Co-design involves users and potential customers into the whole process of product design, from ideation to final design, and thus, has a great potential in offering a personalized customer experience based on the individual needs and behaviors. However, usually co-design requires face-to-face communication, which might be difficult especially in the current corona time. Additionally, it is a challenge for the customer, the non-expert designer to equally collaborate with professional designers. Therefore, a tool is needed to support remote co-design actions and expower the non-expert users for an equal cooperation with designers.

We propose that socialVR, an emerging mediated social interaction technology in the medium of Virtual Reality, has a potential in supporting remote and interactive co-design activities. Social VR technology enables users in different locations to interact with virtual avatars of other users in a collaborative Virtual Environment. Additionally, socialVR allows users to communicate with each other through diverse communication cues (i.e., 3d visual, audio, haptic), and hence, supports intricate social and physical interactions in co-design.

In this project, we aim to explore how socialVR can facilitate co-design, and understand how socialVR influences people’s experience and behavior in remote collaborative design tasks To find out the answers, we follow a research-through-design methodology. Firstly, we choose a specific use case of collaborative cake-making between cake-makers and clients for the purpose of customized retail. Then, based on the current interaction between baker and clients, we designed and developed a medium-fidelity VR prototype, which allows two users collaboratively design cakes in VE wearing head-mounted displays (HMDs). After that, we performed a VR test for user evaluation, so as to investigate the impacts of socialVR on social and collaborative behavior, as well as validate the functionality and interaction techniques of this prototype. The results offer abundant insights for us to understand the how design non-experts experience interacting with professional designers and design systems in socialVR, and how their experience influences their behavior.

Knee osteoarthritis, the most common form of arthritis, which results in stiffness, pain, and impaired movement, is a major cause of disability in elderly populations around the globe. In the course of treating this disease, patients have to endure enormous pains travel to hospitals to meet medical professionals. The motivation behind this project is to support those patients with limited physical mobility to travel fewer times to the hospital but still, communicate well with doctors and nurses. The goal is to build a VR clinic that simulates the real consultation room and facilities in the hospital.
An ethnographic study was conducted at a local hospital in Delft to map the patient treatment journey from the first consultation meeting to the last meetings after surgery. The patient education part of the patient journey was chosen as the focus of this thesis since it involves most of the patient-nurse communications compared to other parts of the journey. Based on the results of the ethnographic study, a social VR clinic was designed and implemented to assist the nurse in explaining the treatment process, and to show the anatomy models and the surgery room to the patient.
The main contribution of this thesis is the design and evaluation of a social VR clinic, based on the use case of knee pain treatment. Future research can expand the consultation to other diseaseses, explore the impact of using more realistic avatars on the VR clinal experience. Other perspectives can be probed into to describe user portraits on their attitude of having VR consultations.

With the growth of global population, the big cities become increasingly crowded. It is not rare to see large crowds in public transportations and events with masses of visitors, such as music festivals and football matches. The question “How to deal with crowds” is receiving attention, both from academia and practical crowd management.
This thesis aims at contributing to a better understanding of crowds from the perspective of individual crowd members’ experiences, including their well- being, emotional experiences and action tendencies. In addition, we want to understand the emotional contagion effect between groups in crowds. To achieve this, we chose to go into the crowds, get in touch with the crowd members, and try to find out what factors sustain their well-being, how their emotional experiences can be measured in a playful and non-intrusive manner, what they tend to do when they have certain emotions, and how the grouping behavior reflects their experiences.

What role patients should assume in medical decision making is an issue that has stimulated much debate. A wide variety of opinions exist, ranging from the view that patients should assume at least some responsibility for their own treatment, to the position that it is unwise to encourage such participation because patients do not have the specialised knowledge required to make treatment decisions (Degner, Sloan, 1992). The difficult process of shared decision making (SDM), is a process in which the physician shares with the patient all relevant risk and benefit information on all treatment alternatives and the patient shares with the physician all relevant personal information that might make one treatment or side effect more or less tolerable than others (King, Eckman, & Moulton, 2011). SDM is currently being advocated by both healthcare professionals and patients as the ideal for decision making (Stiggelbout, Pieterse, & De Haes, 2015). The process of SDM is difficult to implement, for example because it has proven difficult to create access to balanced and easy to understand information for patients. The difficulty of implementing SDM also applies to adjuvant chemotherapy treatment decisions regarding patients with colon cancer. This decision-making moment occurs after surgery when the pTNM-classification (UICC, 2010) shows a certain value which suggests if adjuvant chemotherapy is applicable. During the multidisciplinary consultation (IKNL, n.d.) the best treatment option is discussed in the eyes of the physicians. This is then shared with the patient during the consultation with the oncological surgeon. During the next consultation with the oncologist, it is expected of the patient to make a final treatment decision. Different research methodologies like literature research, semi-structured interviews and observations were performed to obtain the understanding of the current decision-making procedure concerning adjuvant chemotherapy for colon cancer patients. The insights obtained from the observations and semi-structured interviews, were used to create the patient physician experience journey. Combining this with the theoretical framework, the design goal for this project emerged.   The aim of the design process was to Create a User Interface for a web application that ensures that both patient and physician are aware of the different possible treatment options, understand what these treatment options involve concerning risks, treatment options and possible outcome, according to the principles of risk communication, and that interaction can take place, so that the preferences and values of both patient and physician can be shared, to support the process of SDM concerning adjuvant chemotherapy for colon cancer patients. From the patient physician experience journey, combined with the theoretical framework, the IPD was created through multiple iteration steps, involving physicians, patients, and potential patients. The IPD allows the patient to find general information about adjuvant chemotherapy, and triggers the patient to think about their preferences and values concerning quality of life, which can be scored and communicated with the treating physicians. Added to that, the patient and physician are both enabled to gain insights from prediction information about life expectancy. The IPD allows both patient and physician to be aware of the same amount of information and to understand what this information entails, which, according to the literature, is the condition to be able to implement the SDM process properly. Because this project was carried out in the name of IKNL, the IPD was created for a small fraction of the numerical information database they possess, with the purpose to be able to project the principle of the IPD on their entire database to help as many cancer patients as possible with their valuable information. When patients are more involved in making treatment decisions based on the process of SDM, it may have influenced the patient experience in a positive was, leading to a better quality of life of the patient. When the quality of life of the patient is improved due to the provided care, it can be said that the quality of care has also improved.

This project was done for and in cooperation with Karakter Kinder- en Jeugdpsychiatrie, a psychiatric hospital for children. The aim was to give Karakter knowledge and tools to improve the experience of the therapists during the implementation of Jouw Omgeving, a digital environment that allows patient, parent and therapists to communicate about the therapy process. However, the digital environment is not used much by the therapists and thus not by patients and parent either. Qualitative research was conducted with the therapists in order to find out what parts of the implementation could be improved and how the therapists could become intrinsically motivated to use JO. Based on the insight a training was designed that focused on connecting eHealth to personal values and on gaining skills and knowledge to be able to use Jouw Omgeving. The steps of the training were evaluated with the therapists, which led to some changes in the activities of the training.

Nowadays, social interaction is often mediated by technology, which makes it possible for people to interact with each other when they are separated. However, most of these technologies target the interaction between 'weak ties' and they cannot support the naturalness and richness offered through face-to-face interaction. Recently, a new type of mediated social interaction technology, social VR, is opening new possibilities. Social VR technology allows users who are separated to interact with virtual representations of other people in shared virtual environments. These types of social VR technologies are believed to have the potential to create social interactions that are similar to face-to-face interaction.
Efforts are needed to understand how people experience interacting with others in social VR. What are the advantages of social VR that make it different from other social medias, and how can these be used to improve mediated social interaction. Regarding this knowledge gap, the problem defined in this project is to understand the impact of social VR on user experience during social interaction.

This project is divided into six parts: exploring a UX framework for social VR, understanding the photo sharing context, designing an evaluation methodology, evaluating user experience in an experiment, providing design recommendations and reflecting on the project.

In PART 1, the user experience framework of social VR is explored. Several relevant frameworks are selected and compared. These frameworks help us to create a common ground understanding of user experience in social VR.
In PART 2, user experience is explored in a specific scenario - photo sharing between two friends. Context mapping is used to understand the important dimensions of user experience. Three dimensions of experience are identified: Quality of interaction, Social meaning and Presence/immersion.
In PART3, an evaluation methodology is developed according to the research findings in PART 2. This methodology consists of a quantitative part and a qualitative part. For the quantitative part, a questionnaire is developed, based on a set of questions selected from related work. For the qualitative part, a semi-structured interview is designed.
In PART 4, the evaluation methodology from PART 3 is used in a user experience experiment. We compare the experience of photo sharing in Social VR with a Face-to-face situation and a Skype situation. The experiment results show that social VR provide good experience of social meaning as well as presence and immersion. But the quality of interaction needs to be improved.
In PART 5, design recommendations for social VR are proposed, based on the evaluation results from the experiment in PART 4.
In PART 6, reflections on the whole project are provided. Suggestions for future research are given.

With over 300.000 new cases each year, and a survival rate of 50%, oral cancer is a big problem for public health. The primary and best treatment option for oral cancer is surgery. In order to have the best prognosis and quality of life, international guidelines prescribe that the tumor should be removed including a margin of healthy tissue from at least 5mm. However, it is essential not to remove too much tissue, because this will negatively affect the quality of life of the patient.

Most of these procedures are very difficult due to the complex anatomical and functional structures in the oral cavity. Currently, surgeons can only judge the surgical margins by visual inspection and palpation, without much support of technology or other diagnostic techniques. Research has shown that this subjective method results in a very low percentage of successful surgeries. So there is a need for clear and objective information about the resection margins during the surgery.

SurGuide is therefore developing the MarginGuide system. This device uses an optical technique to distinguish healthy tissue from tumorous tissue. It will be used to inspect the margins directly after the tumor has been removed from the patient, which enables the surgeon to remove additional tissue if needed. The MarginGuide should therefore increase the success rate of oral cancer surgeries.

This project focusses on the workstation of the MarginGuide system. The workstation should support the operator in correctly (and easily) measuring and reporting the margins during the surgical procedure. During this project the importance of correct information flow became clear, shifting the focus to software, protocols and the workflow of the workstation.

To establish the different needs and requirements for the workstation, the desired workflow, information flow, and communication of the measurement results are investigated. The research has been verified with surgeons, pathologists and researchers from the Erasmus-University Medical Center.

Based on the results, a software design has been developed. This software design includes the completely designed work- and information flow. This design is supported by anatomical templates, measurement methods, and measurement reports. The anatomical templates can be used by surgeons and pathologist to communicate and save information about the surgery and the resected tumor. Currently, the templates from this project are being used at the Erasmus-University Medical Center for real patients.

The various aspects of the software have been tested separately with the intended users. At the end of the project a complete prototype of the software, workflow, measurement method, measurement report and anatomical templates was developed to test and verify the final designs.

Simultaneously, a design of the physical aspects of the workstation and trolley has been made. The design has been visualised and was verified with the research team at the Erasmus-University Medical Center. However due to time constrains, no prototype has been made for this part of the design.

The National Immunisation Programme (NIP) provides Dutch children with vaccinations for twelve infectious diseases free of charge and on voluntary basis. During several years, the vaccination coverage in the Netherlands has declined (about 0.5 percent per year). It is important to have a high vaccination coverage in order to stop spreading diseases and reaching herd immunity. This herd immunity, of which the minimum percentage differs per disease but lies around 90 percent, protects the people that cannot be vaccinated due to illness or are too young to be vaccinated.

This graduation project focuses on risk communication, presenting both advantages and disadvantages, about the first child vaccinations (DKTP-Hib-Hepb and pneumococcal vaccination between 6 and 9 weeks of age). The project does not focus on increasing the vaccination coverage. The goal is to support (soon to be) parents in a decision making process based on information in order to strengthen those who are positive towards vaccination and help the people who are doubting about participation in the NIP. People who do not have the intention to participate in the NIP are not taken into account. In order to find the most applicable strategy or means of communication, the target group was involved during the whole project.

Different theories about behavioural intentions and decision making processes were examined which has finally led to the model that can be found in Figure 1. This model is based on the normative description of an analytical process of making a choice from Timmermans (2013) represented by the pink boxes. In collaboration with experts, this model is adapted as is visualised by the dotted parts. The short-cuts that are added visualise more intuitive decision making strategies (heart and eye) and a thorough analytical approach that iterates between structuring and evaluation (scale).

Information needs and sources that are used by the target group are found by doing seven interviews with people in the target group. Several ideas with applicable approaches towards communicating the information were formed out of these insights. The ideas led to three design concepts that communicate the information in different ways; positive towards vaccination (focussing on the benefit of herd immunity), as transparent as possible (by showing both advantages and disadvantages) and negative towards vaccination (focussing on the side effects that can occur).

The front pages of the concepts (see Figure 2) are designed for intuitive people. Those who have a more analytical approach will go through the different steps as stated in Figure 1 by opening the leaflet. Recommendations for improvement of these concepts and future research could be made after five concept tests with the target group. The concepts were evaluated and ranked in the test.

The seven interviews that were held and the five concept tests resulted into interpretations of only those people involved. Because only a small amount of participants is used, the data is mainly used for inspiration and not for conclusions about the overall target group.

This project is done in collaboration with the RIVM and VUmc.

COPD (Chronic Obstructive Pulmonary Disease) is a lung disease that causes damage in the patients lung and results in energy and breathing problems. COPD patients often experience a decrease in their energy level. This decrease means they have to adjust their routine and habits and that can be a big challenge. In this graduation project the needs and challenges of COPD patients in regard to energy management are explored. The insights in the needs and challenges leads to a set of criteria. This set of criteria can be used to develop and evaluate e-health solutions that support COPD patients in energy management. Needs COPD patients have two general needs in regard to self-management: autonomy and security. They want to feel secure about their abilities and feel in control of their life. Challenges In order to adjust their routine and feel secure & autonomous the patients meets some challenges. Three groups, with a total of nine of challenges are defined based on interviews with patients. The three groups of challenges are: Keep focus on energy level and act if needed, Find new applicable routine, Put yourself in first place. Needs for support All the challenges of COPD patients lead to specific needs and needs for support. The needs for support are translated into criteria for e-health solution that help COPD patients with energy management. Criteria The result is a list of in total twenty validated criteria. The criteria can be used to evaluate concepts and when translated in a “how to.. “ question as guidens during ideation.

It is impossible to see the light in an empty space, we can only observe light as emission from a light source or reflections from objects. Yet, human observers can estimate the illumination in empty parts of an observed scene, based on the appearance of surrounding objects. This dissertation presents studies on human sensitivity to the light field structure in empty spaces and description of the development of a light visualization tool that implements our knowledge of light fields, light design and perception.

In our perceptual studies, we reconstructed and compared physical and visual light fields. Physical measurements of the illuminance were made in real and modelled scenes with Cuttle's cubic measurement approach. The measurement device was a cube (a simulated one for modelled scenes) with small sensors on each side. The device was positioned over a grid of points in scenes creating regular measurements. For each position six measurements were translated to light properties (intensity, vector direction, diffuseness) with Cuttle's formulas. Then the resulting data was interpolated in order to obtain a full light field. In psychophysical experiments we used a probe proposed by Koenderink et al., a white matte sphere on which the illumination could be controlled by an observer. The task was to make the probe visually fit to a scene or an object. Placing the probe over grids of positions we obtained user data that was proven to be robust enough to reconstruct the global visual light field. We demonstrated that observers' data is robust enough to reconstruct the global structure of the visual light field. We also found that the visual light field is simplified with respect to the physical truth. In particular, it does not reflect subtle variations of the physical light field. In studies on scenes with complex light field structures (i.e. light zones, neighboring light fields with contrasting differences in one or more light properties), we found that observers are quite sensitive to the difference in light properties between the light zones. However, they showed idiosyncratic behavior especially for light zones with diferences in depth of a scene (front-back), rather than in the picture plane (left-right).

The second goal of this thesis was to develop a tool that incorporates our knowledge in measurement and perception of light in its visualization. Modern light visualizations often focus on surfaces or show light in a sophisticated manner understandable only for experts. We augment existing approaches with our tool that visualizes light in 3D volumes and in a perceptually-relevant manner. The measurement approach was the same as the physical measurements used for the perceptual studies above. The measurement cubes could be implemented physically, for real, or virtually, for modelled scenes. Resulting measurements were translated into light properties - mean illuminance, vector direction and diffuseness of light - and represented via variation of shapes' proportions. We tested our visualizations performance compared to image renderings and found that the visualizations led to at least as good task performance as renderings. Moreover, we developed a web-based tool, which can be used for visualizing of cubic measurements by anyone and described applications of this tool for architectural lighting design.

Our findings expand knowledge on the structure of the visual light field and help to understand it better. This can contribute to applied areas, such as computer graphics and architectural lighting design. Moreover, our visualization tool can immediately be used by lighting artists or architectural light designers for increasing their work efficiency by providing quick and quantitative representation of the light conditions.

This Master Thesis describes a graduation project developed to investigate how to help people when disrupted life events occur and how to create strategies to empower them in coping with the situation. It is in connection with the research developed by the PhD candidate Patrizia D’Olivo. To date not many strategies were developed to empower people who suffer of the alopecia condition. Thus, the project attempted to help people with alopecia feel comfortable in their everyday lives by designing coping strategies for the individual with alopecia and anyone he feels close with.
In this project different research and design methods were applied, like interviewing, surveys, a co-creative session and design evaluation with assistance of the Alopecia Vereniging. Context and user research deepened the knowledge on the topic and classified the problems the target group encounters. The disrupted life event of alopecia and the population affected by this condition encounter a lot of problems that differ according to the level of severity and risk. It was evident that the communication between the person with alopecia and anyone he feels close with should be stimulated and improved.
Different design explorations combined with a concept evaluation study and a co-creative session showed the desired features for the final design. The proposed design ‘Imagine alopecia’ gives people close to someone with alopecia a better understanding of the impact of the condition and stimulates the communication between them.
The design evaluation study confirmed that the target group feels that the design has the potential to improve the communication between them and the people they feel close with. In addition, also the people close to someone with alopecia believe in the added value of the design. However, to validate the effect of the design on communication, it should be evaluated by letting people use the design in real life situations.

This thesis presents an approach for 1) analyzing Human Machine Interfaces (HMI) for sub-sea robotic Remotely Operated Vehicles (ROV) 2) structurally redesigning its interface modules and 3) evaluating the resulting designs. The thesis exemplifies this process by redesigning the interface modules that pertain to the diagnosing of hardware failures of the propulsion systems of rock dumping ROVs. The redesign focused on providing the user with more situational awareness.

The aim of this project was to design a product that helps implement a newly developed algorithm to aid in the diagnosis of allergies.

Interviews with allergy patients, allergists, and other specialists were conducted to gain information on their experiences. Literature research was done on recent discoveries on allergy diagnosis.
Information was clustered, and a specific target group was chosen: general practitioners and their patients.
Two concepts were developed and discussed with the target group. One concept was chosen and an interactive prototype was made. A user test was conducted to test usability of the design.

The product that has been developed is an app called Allergenie. The app is used to keep track of food intake, use of care products, and symptoms. The patient can scan barcodes of products with the app, which is linked to a database containing all ingredients. At the end of the tracking period, the patient exports their input into a timeline, which links symptoms to possible allergens that are consumed in the timeframe before the symptoms arose. When an allergen is suspected of causing the patient’s symptoms, the general practitioner orders a blood test using the algorithm.

Using an app to keep track of food, care products, and symptoms was perceived positively by the target group. Being able to scan a barcode and view all of the ingredients will provide more in depth information.
The app and export both proved to be clear and usable by patients and general practitioners.

Every year 550 children are diagnosed with a cancer in the Netherlands. Currently a new hospital is being built in Utrecht, the Prinses Maxima Centrum for child Oncology, this hospital will focus solely on paediatric oncology.

The families that deal with child cancer have to go to the hospital frequently and spend long days there. These days are filled with different appointments and treatments so there is a lot of waiting involved. These waiting times can make the parents feel stressed and the children feel anxious, this results in an elongated waiting experience.

In order to decrease the stress and anxiety the parents and children experience a system was created that provides the families with information and distraction. This system consists of an app for the parents and a basic wearable on a bracelet for the children. Furthermore, the system makes use of portals and patches which create an interactive environment. This system makes it possible for the families to receive notifications about waiting times and can be used to play a game, Parent and child can track each other and send messages to each other. The system gives the parents a sense of control and gives the children a sense of freedom and provides them both with a form of distraction.

Monitoring radio messages while driving is an omnipresent dual-task combination in police work, but it is also one that is considered unsafe for regular drivers. Whereas regular drivers are expected to fully prioritize the driving task, police officers typically do not have the option to stop their car to attend important incoming messages, nor can they afford an uninformed arrival at the scene. A novel method for the visualization of observational data shows that police work is highly fragmented, and suggests that frequent reports on work overload are related to dual- task involvement in this fragmented workflow. Therefore, a series of experimental studies have been conducted to understand the mechanics that underlie and result from task prioritization in a dynamic complex socio-technical system, such as the police context. Methodological implications are presented for the interpretation of tradeoffs between task performance and mental effort as function of task prioritization. Furthermore, practical implications are presented for the development of information technology in police vehicles. Finally, recommendations for future research include the validation of an integrated model on coping strategies, task prioritization, and dual-task switching.

For patients less invasive image-based procedures (IBP) such as laparoscopy have many benefits in comparison to traditional open surgery, such as less pain, faster recovery, and fewer scars. However, to perform IBP effectively, efficiently, and above all safely, the surgical team is highly dependent on technology. The interaction with the surgical instruments and equipment requires extensive training. The proficiency level of the physician and the interaction with the instruments and equipment are key factors in ensuring quality of surgical performance in IBP and patient safety. During surgery, the surgeon should be able to concentrate on the therapeutic tasks. To achieve this, the gap between the preferred and actual level of proficiency of the physician should first of all be minimised by means of preclinical training using simulation tools. In this thesis, the validity of virtual reality simulators for training and assessment of basic psychomotor skills for laparoscopic surgery and flexible lower gastrointestinal endoscopy (colonoscopy) is established. The relation between different IBP skills was also investigated. The performance on two basic laparoscopy tasks (bimanual tissue manipulation and angled laparoscope navigation) proves to be not related; clinically-based expertise in laparoscopic tissue manipulation does not infer skilfulness in angled laparoscope navigation. Training in basic laparoscopy tasks does not affect performance of basic colonoscopy tasks (and vice versa). Training and assessment of basic IBP skills should thus focus on each IBP skill type independently. The influence of specific characteristics of the simulator interface on the efficacy of preclinical training on simulators was also studied. The angled laparoscope navigation task is performed better in an abstract virtual environment than in a virtual environment with simulated anatomic landmarks of the abdomen. And, for training of laparoscopic suturing tasks haptic feedback is a prerequisite. Furthermore, the quality of performance and patient safety should be better safeguarded by improving the interaction with the instruments and equipment in the operating room. Using an integrated operating room system together with the prototype of Pro/cheQ (a digital integrated procedural checklist tool) reduces the number of equipment and instrument related risk sensitive events further than using only an integrated operating room system