Knowledge, Attitudes and Practice Towards Covid-19 Among the Orang Asli Elderly in Peninsular Malaysia

The COVID-19 pandemic has impacted the globe since 2020, and the indigenous people are not excluded, including the Malaysia Orang Asli. They were already among the most vulnerable communities, even before the pandemic, thus, have a higher risk: perhaps the elderly groups are even at the great threat from this alarming catastrophe. A total of 305 respondents from all the 18 Orang Asli sub-groups were involved in this study, with a minimum age of 50 year-olds. Gathering information was done by quantitative data collection using survey techniques. The findings revealed four out of 13 questions about the virus details have the highest number on the misleading details, while the rest are satisfactory. The respondents were not sure if the pandemic can be controlled in general, however, had a strong confidence in the Malaysian government’s responses towards the pandemic. The precautions suggested to minimize the risk were also practised, however, most respondents were not sure when it comes to the specific hygiene precautions. Thus, better-targeted approaches to educating the Orang Asli communities, especially the elderly should be strengthened, to ensure they are not be outdated from crucial information, thus ensuring their wellbeing during the pandemic time.


Introduction
Since COVID-19 pandemic has started in late 2019 or early 2020, tons of efforts have been taken globally to help constraining the pandemic outbreak. Many countries and regions had taken specific or perhaps for some cases, more drastic precaution measurements such as a total lockdown to ensure the pandemic can be controlled. Besides, endless awareness campaigns have been done to educate the people and the society about the facts of COVID-19, its risks, the safety and precaution measurements and the last but not least, the important hygiene practices especially as simple as washing hands frequently and using hand sanitizer.
Started in Wuhan, China, COVD-19 has been declared a global pandemic officially by World Health Organization (WHO). Presently there are more than 167 million positive cases, with more than 3.4 million casualties recorded. In Malaysia, as for 26 th May 2021, there were more than 524 thousand positive cases with more than 2.3 thousand casualties recorded (MySejahtera, 2021). Malaysia also seen it's very first Movement Control Order or known as MCO 1.0. which was more of total lockdown oriented on 18 th March 2020 as a drastic precaution measure to control the outbreak while ensuring the nation's health system is not collapse. This lockdown was seen as a similar step taken by China and Italy, by limiting the non-essential activities: the only allowed activities were going out from home for buying essential groceries or seeking for medical and health treatment (Staff, 2020;New Strait Times, 2020).
During this period and since the pandemic outbreak was still new, there were confusion and mixed understanding towards COVID-19 virus and it risks, and some of the other important general facts such as precaution and awareness related from the people and the community. In fact, the ability of spreading and sharing news, details and information via internet became a double-edged sword, as fast as the actual facts been spread, so did the fake, inaccurate and misleading news and facts about COVID-19 (Mohammad & Azlan, 2020). The people of Malaysia for an example, had mass panic buying and tons of people traveled back to their hometowns. These unexpected and undesired reactions from the Malaysia people could increase more risk of spreading the virus as well the unnecessary panic. Thus, this raised a concern about the Malaysia people's level of understanding, attitudes and practices towards COVID-19. Azlan et al (2020) has adapted the knowledge, attitudes and practices (KAP) approach towards COVID-19, generally among the Malaysia people, via cross-sectional online survey, on which the call of participations was made via social media and online platform. Based on their study, it is found that Malaysians above the age of 50 tend to have higher knowledge scores, while on the other hand, those who with low monthly income tend to have lower knowledge scores. Despite countless efforts been done by the government to educate the people, it is found also that there also has been a surge in false and inaccurate information based on the wrong answers in the survey. Despite some of mixed responses from the survey found, the researchers claimed that most of the respondents have positive responses towards the pandemic and the crisis management.
This paper aims to explore the phenomena among the Orang Asli in Malaysia, especially the elderly group regarding the level of knowledge, attitudes and practice towards COVID-19. Since the Orang Asli are considered as one of the marginalized communities in Malaysia, perhaps a deeper look into its elderly which could be another variable that is worth to look into may provide better insight and understanding on how far the COVID-19 awareness has reached the most high-risk group of the marginalized community which is the indigenous people in Malaysia. This community is considered very important among Malaysian population because they are a distinct group of mainstream society. Indigenous peoples are among the most vulnerable and at risk for this pandemic for several reasons.
First, their geographical location and community characteristics of Indigenous communities are remote and isolated. Economic conditions and limited food resources and facilities services had transformed this group to be vulnerable Sarjit et al., 2010). Secondly, biological factor of indigenous peoples. Most indigenous peoples are elders. Lack of nutrition and disease resistance make them at higher risk of developing COVID-19 (Rosnon, 2020;Sara et al., 2021). Third is the role of Indigenous peoples in their families and communities. Indigenous peoples are vulnerable communities, often living in extended families that continuance multiple generations (Nicholas, 2002). Therefore, isolation in the home does not occur and is vulnerable to this outbreak. Fourth is the culture factor. The whole indigenous community is very close and culturally attached. Older people often play a leading role in their community gatherings, for instance cultural dances, healing ceremonies, or cultural affairs such as death and marriage conduct. Limiting access to older people and community members in cultural management is difficult to implement in the global pandemic (Nicholas, 2005).
In Malaysia a case involving 3 years old child has been reported by a local newspaper. There are two Aboriginal villages under the Restricted Movement Control Order (PKPD) in Sungai Lui, namely the Paya Lebar Orang Asli Village and the Gabai River Aboriginal Village (Rosnon, 2020;Sara et al., 2021). This phenomenon has caused the indigenous people to fear and escaped to the jungle as reported by local media. Indigenous peoples are minorities, both geographically, socially, psychologically and economically, although some of these communities have been incorporated into the mainstream of Malaysian society (Rosnon, 2016;Rosnon & Sara, 2015).

Methodology
This study has utilized a quantitative approach, guided by the research objectives. Since a large number of responses from the Orang Asli people is targeted, a survey is the most suitable instrument in knowing more about the knowledge of, attitudes and practices towards the COVID-19 pandemic among the research subjects (Jones et al., 2013). Data collection was executed physically among the 18 Orang Asli subgroups, with the total of 305 respondents selected based on the respondent criteria. The survey was conducted on 8 th August 2020 to 26 th September 2020, for around 7 weeks period. This period was 5 months right after the MCO 1.0 had been introduced and executed. The focus of the study is on the 18 sub-groups of Orang Asli throughout the peninsular of Malaysia, and with more specific criteria followed which the respondents must be the Orang Asli of the peninsular of Malaysia and minimum 50-year-old, finally there were 305 total of respondents were involved in this study.
Few strategies have been used in reaching out to the selected respondents, mainly by using the recommendations given from the Department of Orang Asli Development, that is known as JAKOA, a government agency entrusted to manage the Orang Asli affairs. From the recommendations obtained, researchers were given a list of suggested Orang Asli villages in the states of Malaysia peninsular, covering the all 18 sub-groups of the Orang Asli. The survey has been conducted via face-to-face interaction: where the survey was offered in Malay language mainly due to the language barrier for English Language, and because of the Orang Asli's familiarity towards the national language (Brislin, 1970). The survey responses were captured in both the survey form and from observation towards the respondents' oral explanation during the survey process.
To measure knowledge about COVID-19, the attitudes and the practices towards COVID-19, the survey elements were adopted and adapted from previous studies from the survey on Chinese residents' knowledge, attitudes and practices (KAP) towards COVID-19 in China (Zhong et al., 2020) and Public Knowledge, Attitudes and Practices towards COVID-19: A crosssectional study in Malaysia  and where a little bit of adaption done mainly on the language structures to ensure the respondents able to understand the survey questions clearly.
The questionnaire consisted of four main themes: 1) demographics, which surveyed participants' socio-demographic information; 2) knowledge about COVID-19; 3) attitudes toward COVID-19; and 4) practices relevant to COVID-19. To measure knowledge about COVID-19, 13 items were adapted from previous research (Zhong, et. al, 2020;. These items include the participant knowledge about clinical presentations (items 1-4), transmission routes (items 5-8) and prevention and control (items 9-13) of COVID-19. Participants were given "true," "false," or "not sure" response options to these items. A correct response to an item was assigned 1 point, while an incorrect/not sure response was assigned 0 points. The maximum total score ranged from 0-13, with a higher score indicating better knowledge about COVID-19. To measure attitudes towards COVID-19, surveyed participants were asked whether they agreed, disagreed or were not sure that the pandemic would be successfully controlled. They were also asked about their confidence towards the government in winning the battle against COVID-19 (yes or no) and about the ability of the government in handling the COVID-19 crisis (agree, disagree, or not sure). To measure practices, participants were asked yes/no questions on whether they had avoided going to crowded places such as weddings; wore a face mask when leaving home; and whether they practiced proper hand hygiene in the week before the movement control order (MCO). For this study, the collected data were analysed using the Statistical Package for the Social Sciences (SPSS), version 26. Descriptive analysis focused on frequencies and percentages.

Results and Findings
A total of 305 participants participated in the study. Out of the total, the average age was 60 years (SD = 7.6), 191 (62.6%) were male, 127 (41.6%) were Negrito tribes, 270 (88.5%) no education and 209 (68.5%) were working. Other demographic characteristics are detailed in Table 1.

Assessment of Knowledge
With the total respondent of 305 Orang Asli people, with the minimum age of 50 years old, from all of the 18 sub-groups of the Orang Asli in peninsular of Malaysia, there were 13 specific questions were asked to respondents to navigate their understanding towards COVID-19 and their awareness level. There were 13 questions were asked to the respondents, covering the topic of the COVID-19 details, the symptoms and precaution measures in which the respondents were needed to choose either 'Agree', 'Neutral' or 'Disagree' with the questions or statements given. Table 2 shows the participant knowledge of COVID-19.

*Correct answers are indicated in bold
Based on table 2 show that, most of the respondents exceeding 50% of the respondents scored well on the correct answers, covering on the symptoms of the virus and the risk assessment (Question 1 -Question 3). However, on the understanding about serious cases of COVID-19 may happen beyond the high-risk groups, the responses received were mixed, which 48% agreed, but the remaining were unsure or disagree of it especially for the elderly group like them which is on the higher risk. This indicates a shallow understanding about the potential risk of severe and serious COVID-19 cases which are not limited only to the high-risk groups (Question 4).
When it comes to dietary practices, the respondents were asked if by eating pr touching wild animals may cause COVID-19 infection (Question 5). While the correct answer is definitely false, the majority of the respondents which was 44% were unsure, with the remaining 33% agree and 23% scored the right answer -disagree. This may result from the Orang Asli common practices of dealing with wild animals, either touching, interacting or consuming the animals as a part of their daily basis. The lowest numbers of respondent scored the right answers indicates the Orang Asli elderly has mixed responses either this daily practice does associate with COVID-19 infection or not, which signify that they do concern and care about their health being over siding on their daily dietary practices. However, the awareness on this particular aspect may be strengthen better.
Another worrying indicator found from the survey is also majority of the respondent with 52% have scored the wrong answer on the question either infected COVID-19 persons are able to spread the infection if they do not have fever. This shows that the Orang Asli elderly's understanding towards the COVID-19 complexity may not in-depth enough, as they able to scored correctly on the virus symptoms, but failed to understand that the infected persons still possess the same risk of spreading the virus without any fever. Nevertheless, the majority of the respondent with 60% have scored a correct answer about understanding that COVID-19 does spread via respiratory droplets of the infected persons. On question 8, it is found as well that the majority of the respondents agreed that the virus COVID-19 was airborne, when the actual answer was wrong. This suggests that the misleading or confusing information existed among the Orang Asli elderly, which could pose another potential and unwanted threat and risk towards them 1 .
The majority of the respondents with high number of 95% agreed that by wearing face mask can significantly reduce the risk of COVID-19 infection (Question 9), and 95% scored on the right answer on the statement that the non-high-risk groups such as the young adults are not excluded from needing to take the same and equal precaution measures to prevent the COVID-19 infection (Question 10). The majority of the Orang Asli elderly also agreed that by avoiding crowded places such as events and public transport, and the 14-days quarantine or isolation period are crucial in helping to prevent the COVID-19 infection, with 98% (Question 11) and 92% (Question 13) of the respondents have agreed respectively. But when it comes to curing the COVID-19 infection, fair number scored the right answer, with 47% of the respondent which is the majority (Question 12), while the remaining have scored on 'disagree' and 'neutral' on the statement that isolation and appropriate treatment are effective ways in managing the spreading of the virus. This indicates that the Orang Asli elderly do have fear towards the COVID-19 virus and infection and almost a fair number of them perceive that these steps are not sufficient enough, which suggest that they may being extra caution and worried about the virus risk, which is a result of them being conscious an aware that as Orang Asli elderly group, they are exposed to the greater risk of the COVID-19 infection.

Assessment of Attitudes
In this section, the total of 305 respondents were asked with questions and statements covering the aspect of their attitudes towards the pandemic and the virus CPVID-19. Figure 1 shows the attitudes of participants on COVID-19. For the first question in this section, they were asked if they would agree that the pandemic can be controlled successfully eventually. From the result, the significant trend can be seen where the majority of the Orang Asli elderly were unsure if the pandemic, in general, can be managed and controlled successfully and eventually, with the total of 54.75% respondents. However, in a smaller scope, majority of the respondents have strong confidence on how the Malaysia government managing the crisis well (with 50.81% agreed), and that the Malaysia government can win the battle against the COVID-19 pandemic (with 69.83% agreed).

Assessment of Practices
In this section, the 305 Orang Asli elderly respondents were asked about their precaution measurement practices in general, to measure how far this respondent group follow the suggested basic precaution measures to prevent COVID-19 virus infection. Figure 2 shows the practices of participants on COVID-19. For the first question, the majority of the respondent with the total number of 78.68% stated that they did avoid crowded places and events, one week prior to MCO 1.0 enforcement. This strongly suggests that the Orang Asli elderly have strong awareness about the happening pandemic crisis even before the MCO 1.0 been executed. The majority of the respondents with the total number of 52.45% fairly agreed that they did wear face masks a week before the MCO 1.0 enforcement, however almost another fair amount of them with 47.54% of respondents claimed that they did not.
In investigating and asking deeper about the hygiene practices, the third question asked the respondents if they did practice a proper hand hygiene which was strongly advised and suggested, to prevent the risk of the COVID-19 infection. Yet, the majority of the respondent with the total number of 60.65% claimed that they did not, while only 39.34% actually did. In a week prior to MCO 1.0, did you avoid going to crowded area / places / events such as wedding ceremony?
In a week prior to MCO 1.0, did you wear face masks when leaving your home?
In a week prior to MCO 1.0, did you practice proper hand hygiene practices such as washing your hands frequently and using hand sanitiser?
Agree Neutral Disagree funnel question, from the most generic and basic practice which is avoiding crowd places, to the very specific hand hygiene practices and using hand sanitizer.

Discussion
The COVID-19 pandemic does affect everyone regardless their demographics and backgrounds. Some of the high-risk groups such as the elderly, the young children and those who have critical illnesses medical history and background are prone to get more severe and serious COVID-19 infection, with more serious complications. In this study, a specific group of the elderly people drawn from the indigenous people of Malaysia which are the Orang Asli in the peninsular of Malaysia not only indicates if the outreaching of the pandemic awareness has reached this high-risk group, but also the marginalised people themselves: the Orang Asli.
When it comes to the assessment of knowledge, on the surface level, the awareness and understanding of the Orang Asli elderly are in the satisfactory level when majority of them have scored correct answers on the basic symptoms of the virus. However, when the survey stepped into another level deeper and more specific detail if the serious complications of the infection may happen beyond the higher-risk groups, the respondents have a mixed answers with almost equally and fairly amount of them scored 'agreed' (48%), 'disagreed' (33%) and 'neutral' (19%). This shows that the Orang Asli elderly are aware about the potential risk of, and threat to the higher-risk groups of people, but lack of conscious that the serious complications may happen to the normal groups of people, even though the probability is lower. This phenomenon may possess another potential risk and threat as the Orang Asli elderly may perceive that the non-high-risk groups of people are excluded and totally safe from the virus: thus, may affect their behaviours and attitudes to become less cautious towards the pandemic.
On the other side, perhaps the Orang Asli elderly have shown a good indicator of being aware and conscious about the COVID-19 infection. As the elder generation of the indigenous people or the Orang Asli, it is fair to say that these people still closely practiced their indigenous practices such as interacting, hunting or eating wild animals: which in this case, most of the respondents have scored that answered 'neutral' with 44% which means they are not sure, neither to believe or to oppose that by interacting and consuming wild animals may cause COVID-19 infection.
With the correct answer is definitely false or 'disagree', this shows that the Orang Asli elderly do consider extra precaution measures related with wild animals, and their native dietary practices in order to being safe and prevent the COVID-19 infection. This extra-caution of awareness shows that the people do care and concern about the pandemic and it's catastrophic infection.
When it comes to COVID-19 symptoms, it seems that the majority of the Orang Asli elderly have scored the wrong answer with 52% that non-fever symptom of the infected persons would not infect other people, while 62% of the Orang Asli elderly have scored the 'Agree' answer that COVID-19 is airborne; which both of the answers are wrong and misleading. On the other side, the majority of them actually have scored a correct answer on the COVID-19 fact that it spreads via respiratory droplet of the infected persons, with 60% scored the right answer. This shown that there might still have some confusion and mixed understanding about how COVID-19 spreads: thus, it is something alarming as misleading information will only make the crisis management and the people's attitudes and behaviours towards the virus worsen the situation.
For the rest of the questions in this section, the majority of the respondents scored well on the right answers of the questions: that wearing masks may reduce the risk of COVID-19 infection (with 95%), the same precaution measures needed to be practiced and taken by the young adult and children just like the high-risks groups to prevent the virus infection (95%), 98% claimed that they avoided crowded places and events a week prior to MCO 1.0 enforcement, and 94% agreed that quarantine and isolation period of 14 days are effective in controlling the virus infection. This shows that when it comes to the infection or outbreak management practices, the Orang Asli elderly were aware and conscious about their responsibilities and the fact that they did acknowledge these even before the MCO 1.0 enforcement shows that they were aware and well informed about these: showing their positive initiatives and attitudes in being responsible and participated in efforts of controlling the pandemic outbreak. The mindset of what were supposed to be taken and be done to control the infection is important as it is the very first layer and level of having a proper understanding about COVID-19 and acceptance that the virus and the pandemic is real and not a hoax. This is even more crucial to indigenous people, per say, even more to the communities since the awareness is among the elderly people as they have influence and potential to affect and educate the rest of the community members.
The first layer and level or understanding and accepting the COVID-19 virus phenomena, however are not sufficient enough in combating the outbreak. A fair number of mixed responses were captured in the respondents' answers on either isolation and appropriate treatment are effective ways in managing the spreading of the virus, with only 47% of the respondents were agreed, followed by 37% disagreed and 16% chose neutral. While the correct answer is definitely 'correct' to this question, these mixed responses shown that there is still fear among the Orang Asli elderly group on how fatal the COVID-19 infection could be, and believing that the current practices of containing and controlling the outbreak may not sufficient enough. This may result from the realization that they are the elderly group of marginalised and less-equipped communities in Malaysia; the Orang Asli.
On the assessment of attitudes, the 305 total of respondents were asked about their perceptions toward the pandemic and COVID-19 infection, and how the Malaysia government manages the outbreak crisis. For the first question, majority of the Orang Asli elderly (54.75%) were unsure if the pandemic can be contained and controlled eventually and successfully, however they did have strong confidence on how the Malaysia government may win the battle against the pandemic (with 69.83% agreed), and that the Malaysia government is managing the pandemic well (with 50.81% agreed). Nevertheless, it is worth to highlight another trend of the responses where 21.86% of the respondents did now have strong confidence towards the Malaysia government to winning the battle, and 37.28% were unsure if the crisis management was handled well. Significantly, it is still can be seen that almost a fair number of respondents had concerns on how this pandemic been handled and managed: which these trends aligned with the first question of this section, where the majority was unsure if the pandemic can be controlled eventually and successfully.
For the last section of this survey, the 305 total of respondents were asked about their practices in preventing the COVID-19 infection. Majority of the Orang Asli elderly claimed that they avoided crowded places and events a week before the MCO 1.0 implementation (78.58%). However, almost a fair and equal number of the respondents did and did not wear face masks when leaving their home, a week before MCO 1.0 implementation (with 52.45 % did and 47.54% did not), and when a specific individual hygiene practice which are washing hands regularly and using hand sanitiser, majority of the Orang Asli elderly (with 60.65%) answered that they did not. This showed that the respondents are aware of the risks and threats of the COVID-19 outbreak, however the number of the people that really practices individual precaution measures such as wearing face masks and proper hand hygiene like washing hands frequently and using hand sanitiser is still not satisfactory. This can be interpreted in due to internal factors rather than external since the data is not synchronized with the first question of this section: such as insufficient resources like face masks, and lack of awareness on the importance of practicing even simple hand hygiene practices like washing hand frequently.

Suggestions and Conclusions
The level of the awareness about COVID-19 virus and it's pandemic outbreak among the Orang Asli elderly captured in this survey are still at the very surface level where they scored well about the infection symptoms. However, the data shown the otherwise when the survey went deeper about more complex symptom and potential risk of the infection, which mixed responses captured were among 'correct', 'wrong', and 'neutral' or unsure. Almost a fair number of respondents were also 'agreed' and 'disagreed' on the more detailed facts on how COVID-19 spreads thus suggests that there a mixed responses and confusion of understanding the facts among the Orang Asli elderly.
A better awareness and outreach efforts are needed especially for the Orang Asli elderly, considering they are on the highest level of the high-risk group pyramid, apart being over 50year-old group of people and from marginalised indigenous communities. These better and specific outreach level must aim on the awareness level about COVID-19 potential symptoms and threats in a more holistic coverage, instead on the surface level. This is crucial to ensure that this high-risk groups of people are equipped with sufficient and adequate number of details, knowledge and information about COVID-19 virus. Confusions that may have risen or misleading information existed among the Orang Asli elderly may and potentially possess more unwanted threat to the indigenous communities in Malaysia, since the elderly plays very important roles in communities, and influencing the communities' members (Obioha & T'soeunyane, 2017).
It is also worth to highlight that the data shown that the Orang Asli elderly had some stepsahead initiatives on being aware and cautions about the COVID-19 outbreak, where fair amount of the respondents willing to compromise their indigenous traditional dietary practices that COVID-19 may spread from interacting and consuming wild animals. However, since the scores captured on their awareness about the virus symptoms and facts: this is a strong evidence indicates that these people are not been informed or delivered sufficient details and information, and it was not due to their lack of interest and awareness about the virus outbreak in Malaysia. Thus, the Malaysia government, NGOs and the rest of the benefactors need to step up the initiatives of outreaching to these people, to make sure they do get correct details and amount of information needed and required, for a better outbreak crisis management in the country (Lee, 2009).
To support this claim, there is a corelation found in data trend from the Assessment of Attitudes where majority of the Orang Asli elderly were unsure about the outcome of COVID-19 outbreak battle, and if the Malaysia government can win the battle and is now managing the crisis well. These are strong indicators of 'unknowingness' that resulted from lack of details and information about the virus outbreak in the nation. This also directly reflect the people attitudes towards the Malaysia government initiatives and credibility in handling the pandemic crisis. The government actually does play important roles in educating the people, outreaching to them to ensure all the details and information are delivered sufficiently to these people (McConnell, 2003).
This survey has also captured a strong inference that the Orang Asli elderly may have lack of resources, and secondly followed by lacking of sufficient details and information on practicing precaution measures and proper hand hygiene like washing hands frequently and using hand sanitizer. To support this claim, the Orang Asli elderly actually scored high on practicing social distances practices, which is something within their control and capability. Thus, Malaysia government, NGOs and the other benefactors may need to look these issues, and make sure that only accurate and sufficient details and information reached to the Orang Asli communities, but also to make sure the required resources like face masks and hand sanitiser are supplied to these communities.

Limitations
There are few limitations found while conducting this survey. Since the survey was done physically where researchers went to the respondents' places based on the networking built, obtained from researchers' and the researchers' academic institution, there is a possibility of bias as the respondents reached may equally spread. Another challenge is also coming from the respondent exclusive criteria where they must be a minimum of 50-year-old: thus, there are limitations to the representativeness of the findings. A more inclusive sampling method may be favored to improve the generalizability and representatives of the findings.
The second limitation of this survey is associated to the KAP instrument adapted from previous studies Zhong, et al., 2020). Due to the limited time and urgency of the survey, the Assessment of Attitudes and Assessment of Practices were measured with minimum number and set of questions and statements (Hamzah et al., 2016;. Better and more specific questions and statements especially on the section of Assessment of Attitudes and Assessment of Practices may be developed for a better navigation and understanding on attitudes and practices towards the COVID-19 pandemic in Malaysia. Since this survey was based on the respondents' self-reported data, another limitation is the possibility of having socially desirable responses and answers, which may not indicate the real scenario and issues studied (Van de Mortel, 2008).