Autism spectrum disorder in architecture perspective: a review of the literature and bibliometric assessment of research indexed in Web of Science

Purpose: An increasing number of scholarly publications on autism spectrum disorder (ASD) have urged researcher interest in this topic; however, there is still a lack of quantitative analysis. Therefore, this study aims to cover the knowledge gap between the amount of literature published on ASD research on architectural and designers' perspectives compared to the medical and psychological fields. The study has analyzed global research output on ASD from a designer's perspective to recognize this gap related to designing the physical environment. Methodology: The bibliometric method was employed to analyze the published literature from 1992–to 2021. 812 papers were downloaded from the Web of Science for analysis based on annual growth of literature, prolific authors, authorship pattern, organizations, countries, international collaboration, and subject development by keywords and thematic map analyses. Various bibliometric and scientometric software was used to analyze the data, namely Bibexcel, Biblioshiny, and VOS viewer. Results: The812 research papers were published in 405 sources. 2019 appeared as a productive year (NP=101), and 2014 received the highest number of citations (TC=6634). Researchers preferred to publish as journal articles (NP=538; TC=24922). The University of Toronto, Canada, was identified as a productive institution with 42 publications and 5358 citations. The USA was the leading producing country with 433 publications, and most of the researchers published in the journal " Scientific Reports" (NP=16). The word autism (NP=257) and architecture (NP=165) were more frequently used keywords. Conclusion: The study identified a massive gap in the development of literature in ASD for architecture design and built environment perspective, the most important and trending keywords are missing, and the analyses also showed a lack of subject development. The authors have suggested areas and keywords for further research to fulfill the gap in the future.


Amendments from Version 1
The authors have conducted a more in-depth study by going through title by title, abstract, and keywords to identify the relevant papers in terms of architectural design and built environment perspective and added three more columns to the table no. 1 for the number of papers in architectural and in design in general with the total number of citations.This addition made a significant difference in version 2 of the paper from version 1.
Moreover, the authors have implemented the suggestions given by reviewers, in terms of extending the literature review by adding previous scientometric studies done on ASD research.The researchers have suggested a few emerging areas of the study and highlighted a few emerging and important keywords which were found missing.Overall, the study has been improved now with more extensive research output.

Background study of ASD
ASD is a neurodevelopmental condition that affects children from a young age.It is marked by functional impairment in social communication, limited interests, selective attention, repetitive habits, as well as hypersensitivity to touch, vision, taste, or sound in certain people (Remington et al., 2009).Autistic disorder, high-functioning autism (HFA), Asperger syndrome (AS), pervasive developmental disorder-not otherwise specified (PDD-NOS), and atypical autism is all diagnostic terminology that has previously been employed.ASD is expected to affect one out of every 88 children in the United States, with one out of every 56 boys being affected.(Taghizadeh et al., 2015).The diagnosis rates for ASD have increased sharply worldwide in the last 40 years compared with other disabilities (Centers for Disease Control and Prevention, 2022) Pallasmaa (2005), diagnosed with ASD, said: 'I confront the city with my body.'The interaction between a person and their environment produces many physical and mental challenges for ASD.Therefore, the built environment is an important factor that significantly influences individuals' behavior directly and indirectly.ASD children are a special case, which should be defined to help them access space and inhabit it.Two issues must be considered to understand the impact of the environment on the development of one's life (Horne, 1997): 1-The identification of the physical environment in its material and symbolic context.

2-
The impact of the environment on one's behavior and how people perceive themselves and their surroundings.
Autistic people have difficulties in processing the information from the physical environment through their senses, especially the influence of environmental stressors like noise and clutter, and they are forced to exert more effort to understand it.The difficulty in understanding provokes frustration and erratic behavior.

Theoretical models of autism
Many human-environment interaction research conducted by environmental psychologists have focused on the environment's psychological factors rather than the physical setting.This section will clarify the relationship between autism and the environment.

1-Human ecosystem (HES)
In 1992, Guerin defined the Human ecosystem (HES) theory model in a learning environment to understand autistic behavior.The variables in this progress are related to the specific model components: a. HO, human organism: gender, age, number of children, and the level of diagnosing b.DE, designed environment: control of entry and exit (safety/security); classroom configuration and adaptability to make changes; lighting (artificial light/daylight); acoustics/noise; thermal comfort (temperature, humidity, ventilation, i.e. indoor air quality); wayfinding; building; FF&E (furnishings, fixtures, and equipment) materials and finishes (color, pattern) (Kopec, 2012;Martin & Guerin, 2010).

c.
NE, natural environment: access to daylight and natural ventilation, as well as green space and/or water (i.e.landscape elements).
d. SE, social environment: visual, auditory, and physical communication method, as well as communication and interaction among children and caregivers in the same physical area.
Some researchers regarding the Nature of autism are convinced that autism is a pandemic of modern culture, with environmental factors at the roots such as pollution; researchers found early-life exposure to air pollution may be a risk factor for autism.(Naviaux, 2012).

2-Performance prediction model (PPM)
The performance prediction model (PPM) describes the transactions between the users and their physical environment through the behavior.Also, understand how the physical environment affects user variables by observing behavior.In addition, clarify the interaction between the three components to lead to universal design principles.Even though this model is not explicitly created for ASD children, the research can be applied to users with different personal characteristics or functional abilities.This model consists of three main components (user variables, behavior, and environment).The variables in this progress are related to these specific components: a. User abilities: individual characteristics and functional abilities.
b. Task outcome: behavior and experiential.

c.
Physical environment: physical characteristics, organization, and ambiance.The characteristics of autism are varied in intensity, degree, and amount and manifest differently from person to person and over time.The common characteristics associated with ASD are loosely based on the DSM-5, common features of ASD, and PMM on ASD.

Sensory function 4. Activity performance
There is limited research on how environments may affect behavior and be designed to meet the needs of those with ASD.Also, there is a lack of information on the experience of spaces and perceptions by people with autism.Only two research have been found namely 'MEDIATE -a responsive environment designed for children with autism (Gumtau et al., 2005) and 'Could light colour and source change mood in children with autism?(Hernandez Rivera, 2020).

3-Theoretical underpinnings of design
Interior designers concentrate on the design of the interior environment with the requirements of the person who will inhabit the space as the driving force behind all design decisions.Human factors, lighting, occupant wellbeing and performance, post-occupancy evaluation, research, theories about the relationship between human behavior and the https://discovery.ucl.ac.uk/id/eprint/10108977/7/Hernandez%20Rivera_ 10108977_Thesis_redacted.pdf designed environment, and universal design are among the ten knowledge areas covered by the 'Human Environment Needs: Research and Application' (HEN) category.
Experts on ASD consider the first six years of school, from preschool to sixth grade, important in reaching children and laying the groundwork for lifelong learning and general wellbeing.
Even when daily activities are meticulously organized, classrooms attended by children with ASD or other children are highly dynamic, unpredictable environments.Because of this instability, examining the architecture of classroom space in schools where children with ASD attend from preschool to sixth grade is difficult.However, the framework identified by (Guerin, 1992), which recognized the interaction of the human organism (HO), the BTE, the natural environment (NE), and the behavioral environment (BHE).
Autism spectrum disorder (ASD) is a complicated neurological disorder that, until now, has been inscrutable.The population of individuals on the spectrum worldwide is increasing due to the increased awareness.As their numbers grow, professionals in many fields started studying their ASD cases to provide them with a better life (Hauptman et al., 2019).Individuals on the spectrum are part of a growing population usually ignored in design despite the current tendency to create designs that focus on persons with special needs.There are binding recommendations and laws on designing buildings that respect physical disabilities, and the field is rich in design applications for physical needs (Sánchez et al., 2011).By contrast, there is utter indifference toward the person with mental health disabilities, even with guidelines for inclusion of children with physical impairment are used and successful, the inclusion of children with mental disabilities lags much behind (Bilbo et al., 2015) in their research mentioned that "the environment plays a role in human behavior" that greatly influenced the practice of interior architects designing people centers design.ASD children have sensory processing difficulties, which create challenges in understanding the surrounding environment, thus affecting their behaviors negatively (Sánchez et al., 2011).The built environment can cause extra confusion, which negatively impacts children with ASD due to the challenging developmental disorder of the ASD.Architects and interior architects are responsible for providing an inclusive built environment to improve the quality of life, especially for people with special needs (Kopec, 2012), yet it is still relatively unnoticed by architects and designers as it's still excluded from building codes or design guidelines.Environmental and behavioral research has profoundly influenced the practice of interior architecture as it's vital to explore the environmental design for autism.
A vast amount of literature has been published on autism in medical and psychological journals over the years.However, few studies from an architectural perspective have been published even though the role of the sensory environment in autistic behavior has been an issue of debate since Leo Kanner first defined the disorder in 1943 (Kanner, 1943).Recently, architects have become interested in finding out about the relationship between environment and autistic behavior to provide a suitable environment and support wellbeing.
Few interior designers and architects have yet started to define codes and guidelines such as Autism Planning and Design Guidelines 1.0 by Knowlton School of Architecture (2018) as a design solution for ASD to build autism-friendly surroundings that support users with ASD and prepare them to face other environments.The designer's approach usually compares children with ASD and without through their behaviors to find the differences in their needs in the environment (Delmolino & Harris, 2012) The above general studies conclude that most literature is based on medical, biotechnology, and psychological perspectives.
Most funding agencies are identified as medical institutions, and the US is the most contributing country to generating the literature.Most ASD research in article form and double and triple authorship has more consideration.The citation rate shows an increase in the trend, and the growth in ASD research literature in terms of medical and psychological are noted as a steady increase and are higher in this decade.
However, the development of ASD literature in the architectural field has not been found.Therefore, based on the scientometric analysis, the present study considers estimating and identifying the gaps in the available literature on ASD from the architectural perspective compared to the literature available from the other perspectives, such as medical and psychological.

Results and discussion
From 1992 to 2021, 405 sources were contributed by 5088 authors with 812 papers in autism.Single authored documents were 61 papers; hence authors in autism produce more research in collaboration.The average number of years of publications is 5.74, the average number of citations per document 43.21, and the average number of citations per year per document 5.711.36,654 references have been consulted to produce 812 research papers.The number of documents per author is 0.16, authors per document are 6.27, Co-authors per document is 8.16, and the collaboration index is 6.71.
Annual research growth and citation's structure in autism spectrum disorder during 1992-2021 The first research paper on autism was recorded in 1992 with 382 citations (no publication indexed in 1993, 1995, 1996, 1997, and 2003), similar results reported by (Kumar et al., 2021).
Though the research output gradually increases, but shallow up until 2012.The autism research increased markedly after 2013, noticeably more than 50 papers appeared every year after 2013.The year 2019 was the most successful in term of the number of the article (NP=101), followed by the year 2016 and 2017, in which the second highest number of research papers published, coincidently the year 2018 and 2020 have equal number published articles (NP=84) and the year 2021 have 35 papers with 19 citations.The highest number of citations received in 2014 (TC=6634) for 53 publications, followed by the year 2011 (TC=4078) for 31 papers and the year 2010 (TC=3108, TP=34) (Table 1).
The authors have scanned all these documents to pinpoint the exact number of research papers purely on architectural design perspective and found a quite low number also, some of it belongs to art and design, these numbers represent the actual gap in the literature, which authors intended to explore and found that gap is quite huge.See (Table 1).
The approach to educating future designers to design autism schools," by Love JS, published in ARCHNET-IJAR, received only 2 citations.Three research papers were published in 2019 under the title Quality of the built environment from the point of view of people with autism spectrum disorder", "The impact of color and light on children with autism in interior spaces from an architectural point of view," and "Studio teaching experiments-spatial transitioning for autism schools" begged 0, 1,1 citations respectively.During pandemic 2020, only one research was published and didn't receive citations, and in 2021 (continuing years) didn't notice any research.Therefore, only 16 ASD research papers were purely related to architectural design from 812 documents noted from 1992 to 2021, with as many as 11 citations.These number of documents and citations reveal that these research areas are not very popular amongst the researchers.Please refer to the recent growth in general ASD research (Ozgur & Balci, 2022), as mentioned in the literature review.

Type of research papers
The journal articles (NP=537) were the most preferred form, which agrees with (Rahaman et al., 2021b).The review found a second preferred form (NP=142), followed by proceedings papers (NP=71) and then meeting abstract (NP=17).Other documents were minor in the list, published only three papers each.
On the other hand, the articles also received the highest number of total cations (24922), followed by review (TC=8916) (Table 2).The research was purely based on an architectural perspective, mostly published as journal articles (13) and then as proceeding papers (3) out of 16.Please refer to (Table 1) for the total number of pure architectural design research.

Productive organization
It is evident that the top ten organizational productivity ranges between 25 to 42 publications (Table 3).The University of Toronto is the leading organization in autism research (NP=42), followed by Vanderbilt University (NP=37), University of California, Los Angeles (NP=35), Yale University (NP=33), and Massachusetts General Hospital (NP=30).Harvard Medical School (NP=25) identified as the minor producer of research in the top ten list.Interestingly, most of the listed organization are in the USA (9 organizations), and one organization from Canada.Stanford University was the most cited organization (TC=6686) for 28 publications, followed by Yale University (TC=6059) for 33 research in autism.

Productive country
Moreover, it is found that the top eight countries produced over 50 research papers (    Dalton C; and Love JS.Shareef SS; Farivarsadri G received one citation for one paper, and the other nine authors didn't receive a citation.

The pattern of authorship
The Figure 2 illustrated the pattern of authorship in autism literature.It was clear from the figure that the authorship pattern ranged from single to two hundred and forty-seven.The analysis reveals that collaborative research is more prominent among the research of autism over the study period.The top six authorship patterns produced over 50 publications in the field.Three authorship patterns (NP=123) contributed a maximum article in autism, followed by two authorship (NP=120), four authorship (NP=93), five authorship (NP=79), single authorship (NP=61), and six authorship (NP=56).The authorship of 27, 36, 38, 39, 40, 42, 46, 56, 58, 65, 67, 73, 86, 88, 118, 125, 146, and 247 each contributed only single publications in autism.The results also showed that two authorship patterns received the highest number of citations (TC=4775), followed by five authorship (TC=3296) and Three authorship (TC=3071).Rahaman conducted a similar type of authorship pattern analysis (Rahaman et al., 2021a).
Mapping co-occurrence of all keywords (author and indexed) Figure 3 shows analysis of all keywords used in autism research from 1992-to 2021.The results showed that 3848 keywords appeared in autism research.To map the co-occurrence of all the keywords, minimum of 15 occurrences of keywords were considered for analysis.Out of 3848 keywords, only 79 keywords met the thresholds, and all 79 selected keywords are clustered in Figure 3 with 1737 links and total link strength (5557).The size of the ball indicates a strong network of keywords, with each color representing a distinct cluster.
Each cluster is based on the theme, which shows the various aspect of the subject and its development.The themes special for architecture or design or built environment are missing to track the development of the subject.

Thematic map by title
Figure 4 shows four alternative typologies of themes that can be visualized using a thematic map.The thematic parameter is considered the title selected for the field, the minimum number of words selected is 80, and Unigram is selected for the graph.
Emerging or declining theme: study genome represented by cluster 4 (study, genome, association, wide and evidence).

Most cited research papers in autism
The top ten papers (  et al., 2011), and "A genome-wide scan for common alleles affecting risk for autism" was the least cited paper among the top ten (393 citations) (Anney et al., 2010).It was noticeable that half of the top ten cited papers were published by Nature Publishing Group.The article entitled "Synaptic, transcriptional and chromatin genes disrupted in autism" (De Rubeis et al., 2014) has the highest total citations per year (152.50).
The papers that are well received in architecture or architectural design are not listed here due to a lack of citations than the papers in the other fields; hence, the ASD research in the given fields is less prevalent.The most cited papers in the architectural field are: ' The building process as a tool towards an all-inclusive school.et al., 2012).However, the top ten listed references belong to the biotechnology, genetic architecture, and medicinal aspects; the gap identified here is the lack of ASD study on architectural in terms of designer perspective.

Highly influential funding agencies
There are only four funding agencies from the top 10 list which funded more than 100 research papers (Table 9).National It is to be noted that all funding agencies belong to the health and medicine except one that is the 'UK Research Innovation,' which is a good sign for the researcher belonging to the field of innovation, architecture, design, and creativity to apply for a funded research/projects.

Country collaboration in autism
The most dominant country collaborations were the USA and United Kingdom (51 publications), followed by the USA and Canada (43 publications), the USA and China (38 publications), the USA and Italy (26 publications), and the USA and the Netherlands (26 publications).The USA with Sweden collaboration (19 publications) was listed at the bottom of the top ten list.It was interesting to show that the USA collaborated with nine countries (the UK, Canada, China, Italy, the Netherlands, Germany, France, Australia, and Sweden).The UK followed this with two countries (the USA and Canada).

Conclusion
This bibliometric study has been proposed to cover the knowledge gap between the amount of literature that has been published on autism in medical and psychological journals over the years and the published research with the architectural and design approach.However, no other bibliometric analysis has been done from 1992 to 2021 that comprehensively evaluates and summarizes the literature, progress, and future directions of this key sub-area of ASD research.The results are eye-opening since only 16 out of 812 papers retrieved are purely relevant to the architectural and designers' perspective.The other papers are medicine, psychology, biotechnology, ICT, computer software design, etc.
The keywords and thematic analyses identified the huge missing gap since all are too generic, therefore, the authors have identified a few missing keywords, which leads them to suggest that more ASD research needs to be done in terms of built environment characteristics, negative sensory experiences, and conducive design features.
The literature review indicated that the performance prediction model (PPM) needs more research since, for over 2 decades, only 2 projects (cited in literature review) focused on describing the transactions between the users and their physical environment through the behavior.It also suggested that designers need to work more in defining codes and guideline to build autism-friendly environment to support people with ASD.
The top ten analyses of the country, institution and funding agencies show that the USA is highly active in producing ASD research.Stanford University is noted as the most cited organization might be due to its own program for Autism research, extending a good platform for the researchers in this field.The 'UK Research Innovation' is the only funding agency to provide opportunities to researchers in design and innovation.This research also leads researchers to discover the most influential publications, authors, and journals in this field.
Here Reviewer Expertise: I have enough knowledge in the field of bibliometric and scientometric studies.
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
First, the introduction and the literature review should be extended with a description of bibliometrics, evidence of its successful use (and the reason why they selected bibliometrics as a knowledge synthesis method), the bibliometrics tools used should be shortly described and their use in the study stated more clearly.There are already some bibliometrics studies on autism and other disabilities already published, authors should point to them in the literature review and connect their research to already performed studies (they should also compare their results to results of similar studies in the discussion section).
In the results section, they should point out which bibliometric tool was used to produce them.
The results should also be extended with qualitative aspects, actually, the discussion is mostly missing.What is the meaning of the results, who can use them, and for what purpose.In the conclusion, authors mention that research gaps, research directions could be derived from their results, but the readers could benefit much more if the authors themselves will reveal hot topics, gaps, directions, etc. Authors should describe revealed clusters from keywords analysis in more detail.They should use thematic or content analysis to name and describe clusters, point to relevant literature, etc. Reviewer Expertise: Computer science, bibliometrics, machine learning, health informatics I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above.

Is
Comment of reviewer: The authors performed an interesting bibliometric study.They focused mainly on quantitative aspects of the research on autism-related architectural design.However, the paper should be amended in some aspects to make it more informative for readers and to make the study repeatable.
○ Authors Response: Done, the authors have worked more on the dataset and amended the annual literature growth table 1 to compare the literature growth in general with literature growth from the architectural and designers' perspective.
Comment of reviewer: First, the introduction and the literature review should be extended with a description of bibliometrics, evidence of its successful use (and the reason why they selected bibliometrics as a knowledge synthesis method), the bibliometrics tools used should be shortly described and their use in the study stated more clearly.There are already some bibliometrics studies on autism and other disabilities already published, authors should point to them in the literature review and connect their research to already performed studies (they should also compare their results to results of similar studies in the discussion section).
○ Authors Response: Done, the introduction and the literature review have been extended and previous bibliometric studies included and compared the results.
In the results section, they should point out which bibliometric tool was used to produce them.The results should also be extended with qualitative aspects, actually, the discussion is mostly missing.What is the meaning of the results, who can use them, and for what purpose.In the conclusion, authors mention that research gaps, research directions could be derived from their results, but the readers could benefit much more if the authors themselves will reveal hot topics, gaps, directions, etc. Authors should describe revealed clusters from keywords analysis in more detail.They should use thematic or content analysis to name and describe clusters, point to relevant literature, etc.
○ Authors Response: Done, all the issues raised have been addressed.
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Figure 1 .
Figure 1.Four phase flow chart of data extraction and filtration process.

Figure 4 .
Figure 4. Thematic map by title analysis.
the work clearly and accurately presented and does it cite the current literature?Partly Is the study design appropriate and is the work technically sound?Partly Are sufficient details of methods and analysis provided to allow replication by others?Partly If applicable, is the statistical analysis and its interpretation appropriate?Not applicable Are all the source data underlying the results available to ensure full reproducibility?Yes Are the conclusions drawn adequately supported by the results?Partly Competing Interests: No competing interests were disclosed.
Universal design: equitable use, flexibility in use, simple and intuitive, perceptible information, tolerance for error, low physical effort, and size and space for approach and use. d.

Table 1 . Annual research growth and citation's structure.
*NP=Number of Publications **TC=Total Number of Citations

Table 2 . Type of research.
*NP=Number

Table 3 . Top ten organization-wise research in autism.
biology, and biological psychiatry; this top ten listing lags the source in the areas of architecture or architectural design.Hence, the authors have further explored the sources in which the 16 research papers purely on architectural design have been published.They found very few but popular sources in the field, namely, Archnet-IJAR International Journal of Architectural Research, International Journal of Arts and Technology, Housing Studies, Journal of Housing and the Built Environment, Journal of Intellectual Disability Research, Journal of Policy and Practice in Intellectual Disabilities, Advances in Human Factors, Sustainable Urban Planning, and Infrastructure.amongst them Tufvesson C; Tufvesson J, and Nagib W; Williams A contributing one paper and begged 11 citations, followed by Kinnaer M; Baumers S; Heylighen A (NP=1, TC=8), Mcallister K; Sloan S (NP=1, TC=7).The other authors with one paper received two citations are Segado Vazquez F; Segado Torres A;

Table 6 . Top ten most productive authors in autism research.
*NP=Number of Publication **TC=Total Number of Citations

Table 7
(De Rubeis et al., 2014), "The contribution of de novo coding mutations to autism spectrum disorder" (2014) by Iossifov I, published in Nature (1118 citations)(Iossifov et al., 2014), "Mapping autism risk loci using genetic linkage and chromosomal rearrangements" (2007) by Szatmari (999 citations)(Szatmari et al.,  2007)."Dendritic spine pathology in neuropsychiatric disorders" (2011) by Penzes (838 citations) (Penzes Most Cited references in autism researchTable 8 explained the most top ten cited references in autism research.It is clear from the table that all listed references received more than 50 citations.Article entitled "Insights into

Table 7 . Top ten cited papers.
*N/TC=Normalized total citation

the work clearly and accurately presented and does it cite the current literature? Yes Is the study design appropriate and is the work technically sound? Yes Are sufficient details of methods and analysis provided to allow replication by others? Yes If applicable, is the statistical analysis and its interpretation appropriate? Yes Are all the source data underlying the results available to ensure full reproducibility? Yes Are the conclusions drawn adequately supported by the results? Yes
. The analyses, results, and interpretation display interesting and beneficial data.Moreover, quality of the text is good.There are a few unnecessary capitalizations in the sentences, but ignorable.Overall the paper represents valuable information regarding autism spectrum disorder in architecture research.
collaborationCompeting Interests: No competing interests were disclosed.