Principles for Achieving Legibility in Residential Spaces: A Synthesis of Cognitive and Perceptual Approaches

Abstract

The legibility of residential space pertains to the clarity and intelligibility of spatial organisation, facilitating intuitive navigation and an immediate grasp of spatial structure. Despite its significance, legibility remains an underexplored factor in residential design, particularly regarding its cognitive impact on users. This study investigates key determinants of legibility, including spatial layout, circulation patterns, lighting, and colour schemes. Through theoretical and empirical approaches, a literature review and case studies identify fundamental principles shaping residential legibility. Unlike previous studies, this research integrates both objective spatial cognition tests and subjective user perceptions, offering a more comprehensive understanding of legibility. The experimental component examines cognitive navigation and subjective perception, assessed via the recognition of a 3D interior from a 2D plan and bipolar rating scales. Participants explored regular and irregular layouts through animated simulations. Findings confirm that experts exhibit greater spatial recognition accuracy and that legibility is enhanced by spatial regularity and distinct colour schemes. However, lighting had no significant impact on subjective assessments, indicating that its role in perceived legibility may be overstated. These findings provide new insights into how spatial legibility affects cognitive processing, distinguishing this study from prior research and advancing practical design strategies for optimising residential environments.

1. Introduction

In architecture, spatial legibility refers to a set of characteristics that enable users and visitors to navigate and comprehend a space with ease. Spatial legibility significantly impacts the functionality of residential environments by facilitating intuitive wayfinding, efficient space utilisation, safe movement, and the smooth execution of everyday activities. When a space features a well-defined room layout, logical circulation flow, and clearly positioned elements, users can move through it without confusion. Moreover, an understanding of spatial organisation allows occupants to optimise their movement, locate objects and functions more easily, and make more efficient use of available space. Additionally, a well-structured and clearly organised space reduces the risk of accidents and injuries. Users are better able to detect obstacles and potential hazards, which is particularly crucial for individuals with reduced mobility, such as the elderly or persons with disabilities. Enhanced spatial legibility also facilitates the performance of daily activities, contributing to an improved quality of life and overall user satisfaction. Furthermore, legible spaces can positively influence social interactions, which is especially relevant in the context of hospitality. A well-structured environment fosters a welcoming atmosphere, making guests feel more comfortable and at ease during their stay.

1.1. Theoretical Perspectives on Spatial Legibility

The concept of spatial legibility in residential architecture has not been extensively researched, despite its significant role in achieving functional efficiency. Several factors may explain this lack of attention, ranging from the possibility that spatial legibility has not been recognised as a critical research topic to the fact that it has received less focus compared to other technical aspects of architectural design. While spatial legibility has been extensively studied in public and urban environments, its role in residential design remains insufficiently explored. The lack of research on how residents cognitively process and perceive their living spaces results in design approaches that may overlook key factors influencing intuitive navigation, functional efficiency, and overall well-being. Existing studies primarily focus on objective spatial attributes, neglecting the interplay between spatial structure and users’ subjective experiences. Addressing this gap is crucial, as ineffective spatial organisation can lead to cognitive overload, reduced usability, and diminished comfort in residential environments. However, a key reason could be that spatial legibility is inherently subjective, as it largely depends on individual user preferences and needs.

In the field of urban design, the concept of legibility has been widely discussed. Most interpretations trace their origins to Kevin Lynch’s assertion that legibility refers to the ease with which parts of a space can be identified and arranged into a coherent pattern [1]. Kevin Lynch’s concept of legibility, initially developed for urban environments, is equally relevant in residential spaces. While his work primarily addresses the clarity and navigability of cityscapes, the same principles such as the role of landmarks, paths, and spatial organisation in facilitating intuitive wayfinding apply to interior layouts. In residential settings, spatial legibility influences how occupants cognitively map their living environment, affecting both usability and comfort. Therefore, adapting Lynch’s framework to residential architecture helps bridge the gap between urban-scale legibility and the micro-scale of home environments.

According to Labin, spatial legibility represents the ability of individuals to organise visual information from their surroundings effortlessly, allowing them to establish a meaningful basis for their activities [2]. Wang et al. define legibility as the degree to which a space can be easily recognised [3]. Tavassolian and Nazari argue that urban legibility involves the straightforward recognition of city components and their integration into a coherent whole [4], a stance echoed by Koseoglu and Onder, who describe legibility as the ability to organise the environment into a recognisable and structured form [5]. Discussing urban design factors, Rezafar and Turk state that legibility is the clarity of a space’s image, making it easy to comprehend [6]. Khullar posits that the legibility of small urban spaces depends on the presence of recognisable and expected elements and that the absence of distinct features may hinder their perception and memorability. By developing a methodology for identifying these elements, it is possible to improve the understanding of how people perceive and navigate urban spaces, which could enhance urban design quality [7]. According to Miles, legibility results from the perception of a city’s visual landscape, wherein various formal elements integrate into a unified whole. While spatial legibility is not inherently given, it can be deliberately shaped through design [8]. Taylor, however, argues that legibility is not as significant a criterion in the perception of urban landscape quality as aesthetic appeal. He considers the concept of legibility in urban design, while important, to be generally overrated [9]. From the perspective of Vatkevičiute, legibility is an urban characteristic that defines an individual’s ability to navigate within an urban or architectural structure, as well as to understand the identity or function of a given space. A legible environment aids not only in situational spatial awareness but also in comprehending the city as a whole [10]. Xu, Rollo, and Esteban’s study introduces a space syntax-based methodology to examine the influence of spatial characteristics on the perception of historical streets, integrating urban design and environmental psychology principles to enhance spatial understanding and support the development of more effective policies for the preservation and revitalization of historical urban landscapes [11].

In the field of architecture, Ahmed, Taha, and Hasan explore an evaluation model for improving wayfinding in complex buildings. The authors conclude that the primary factors facilitating orientation and navigation are building configuration and its level of complexity, followed by architectural differentiation, visual accessibility, and the presence of landmarks [12]. Cheng and Pérez-Kriz argue that an ideal spatial structure should facilitate users’ movement within a building. Orientation is enhanced when different zones are visually differentiated, when users can identify internal or external reference points, when the building layout is simple and regular, and when the number of decision points and corridor intersections is minimised [13]. Soltani and Ghasr approach legibility from the perspective of the functionality of office buildings, examining how different typologies and physical contexts influence interior legibility and user orientation, with the aim of improving future office space design [14].

In the domain of interior organisation and residential design, Knežević emphasises the role of legibility in structuring residential space, asserting that it is closely linked to apartment zoning. According to the author, spatial legibility is determined by three key factors: (a) clarity of layout, (b) balance between zones and within individual apartment areas, and (c) logical sequencing of spatial connections within the apartment [15]. Afghantoloee, Mostafavi, Edwards, and Gharebaghi argue that spatial legibility is not solely dependent on visibility, connectivity, and layout complexity, but also on individual user factors, particularly for individuals with motor impairments. Their findings highlight the need for a personalised approach to assessing spatial legibility [16]. Al-Amaireh examines spatial legibility from the perspective of the complexity of contemporary architecture, emphasising that advanced technology and minimalist design can impede orientation, particularly in large-scale buildings such as shopping centres and hospitals. The author stresses the importance of a comprehensive study of interior legibility through methodological approaches such as the modelscope technique [17]. Abdulpader, Sabah, and Abdullah explore spatial legibility through the lens of architectural flexibility, highlighting how adaptive interior spaces, including flexible layouts and interior elements, can enhance functionality, economic sustainability, and housing quality in densely populated urban environments [18].

In the field of cognitive psychology, Carlson et al. [19] highlight that wayfinding difficulties in buildings can be explained by three key factors: the spatial structure of the building, the cognitive maps that users develop during navigation, and movement strategies, which vary depending on individual spatial abilities. The authors emphasise the importance of aligning these factors and propose an integrative framework to understand how they collectively facilitate or hinder spatial orientation [19].

Spatial legibility or clarity can depend on various parameters. Several studies have examined the factors influencing spatial legibility [20,21,22,23], concluding that wayfinding is facilitated when (a) locations (areas or zones) are visually differentiated from one another; (b) users can identify internal or external landmarks that aid orientation; (c) the layout and spatial arrangement are logical, easy to comprehend, and follow an identifiable order or pattern; and (d) there are fewer decision points along movement routes, such as intersections or crossroads. While these factors primarily pertain to urban spatial legibility, certain parallels can also be drawn in the design and organisation of interior spaces. The subsequent sections of this research will further explore the key factors influencing residential spatial legibility.

Based on a review of existing studies, it can be concluded that spatial legibility is examined from multiple disciplinary perspectives, including urban design, architecture, interior space organisation, and psychology. In urban contexts, legibility is typically defined through the perception and organisation of visual information into a coherent pattern. In architecture, the focus is placed on building configuration, complexity, and visual differentiation, which facilitate orientation. In interior space organisation, legibility is closely related to zoning logic, layout clarity, and relationships between functional units. Meanwhile, in psychology, research highlights the importance of cognitive maps and individual spatial abilities.

Although many authors emphasise the subjective nature of spatial legibility, linking it to an individual’s ability to organise and interpret visual information [1,2,3,4,5], this study additionally considers the objective characteristics of a space that contribute to its legibility. Therefore, the primary focus of this research will be the identification and systematisation of key parameters, such as structural regularity (room arrangement and shape), movement lines (flow and efficiency of circulation), colour schemes, and lighting conditions, which collectively impact the legibility of residential spaces.

1.2. Key Principles for Achieving Spatial Legibility

1.2.1. Rooms Layout

The arrangement of rooms plays a crucial role in achieving spatial legibility in residential design. To ensure that a dwelling is easily comprehensible and pleasant to use, it is essential to establish a logical flow of movement, providing users with a sense of continuity and spatial connectivity. This involves creating a clear and uninterrupted circulation path from the entrance to different zones within the dwelling. Each room should be well-defined and strategically positioned, allowing users to immediately recognise and understand its function within the overall layout. A well-structured room configuration facilitates intuitive navigation and enables users to make the most efficient use of the available space. The internal connectivity of rooms is fundamental, with open-plan layouts—such as those integrating the living room, dining area, and kitchen—significantly enhancing spatial continuity and fostering communication between different zones. For instance, organising a residential space with the living room positioned opposite the entrance establishes a direct line of movement, not only delineating functional zones but also guiding visitors towards the central area of the home. This type of layout serves as a model for creating legible residential spaces, where a carefully planned room arrangement enhances orientation and comfort for occupants.

The perception of layout clarity begins at the entrance, where visitors should immediately gain an understanding of the dwelling’s size and spatial organisation. To achieve a clear and legible interior, the social zone should be closely connected to the entrance area, meaning that access to the social zone should align with the primary axis of entry into the dwelling. This connection can be either direct or indirect, depending primarily on the size of the dwelling and the arrangement of key functional groups. According to Knežević, the proportional relationship between different zones is equally important, as it dictates the circulation flow within the home. When these relationships are well structured, users find it easier to orient themselves and comprehend spatial connections between rooms, thereby improving the overall legibility of the dwelling [15]. Figure 1 highlights six possible configurations of primary functional groups within a residential unit, demonstrating how different spatial arrangements influence spatial legibility. The first configuration (top-left) aligns with the organisational principles observed in the Cerak Housing Estate, where the living room and household areas are spatially distinct, facilitating both ease of movement and functional efficiency. In contrast, other configurations illustrate varying degrees of spatial clarity depending on how living room, household, and private areas are positioned relative to the entrance (Figure 1).

A characteristic example supporting this assertion is the apartment layout in the Cerak residential estate in Belgrade (Marušić, Marušić & Borovnica, 1981), where the living room is positioned on the opposite side of the entrance. This arrangement clearly establishes a linear circulation axis (“spine”) that directs visitors towards the centre of the apartment while simultaneously delineating the space into primary functional zones (as illustrated in Figure 2). By positioning the living room deep within the apartment, a clear separation is achieved between household and private spaces, ensuring intuitive navigation and reinforcing the spatial hierarchy. The presented organisational model ensures spatial clarity upon entry, thereby enhancing the overall perception and legibility of the space. This concept is further reinforced by a statement from one of the apartment’s designers, who emphasised that “a good apartment is one where you can enter at noon without turning on the lights, allowing you to enjoy daylight streaming through double glass doors, which you can open directly without having to search for an entrance to the left or right along the hallway” ([25] (p. 13)).

1.2.2. Flow and Efficiency of Movement

The movement flow from the entrance to various rooms should be clear, logical, and, above all, practical. The absence of obstacles, sufficient width for unobstructed passage, and well-positioned straight corridors within the circulation structure of the apartment are crucial for seamless navigation and ease of movement. This layout should feel natural and intuitive, allowing users to move freely without a sense of restriction. At the same time, the spatial arrangement should be functional and tailored to the everyday needs of the occupants. Such an organisation minimises unnecessary walking or traversing long distances, thereby enhancing movement efficiency within the apartment. Efficiency of movement is a key parameter in grouping compatible functions within a residential space. When related functions are clustered or closely connected, users expend less effort searching for specific areas, facilitating daily activities and making the living environment more comfortable. This approach to residential space organisation contributes not only to spatial legibility but also to overall functionality, enabling users to live and work in an environment where time and energy are not wasted unnecessarily.

Characteristic examples supporting this observation include apartments in the Đuro Đaković housing estate in Sarajevo (Dragičević, Stanković & Savčić, 1975), Julino Brdo in Belgrade (Janković & Stjepanović, 1966), and Banjica in Belgrade (Karolić, Pavković & Stojanović, 1971) [27] (Figure 3). In all three cases, the clarity of spatial organisation stems from the linear axes extending across the space, effectively grouping residential functions into orthogonal units. However, despite the fact that these examples were not realised, they provide a clear illustration of how rectilinear and orthogonal movement routes can be instrumental in the organisation and perception of residential space. These spatial configurations directly inform this study’s hypotheses by demonstrating how different circulation strategies influence movement efficiency and spatial legibility. Specifically, the examples highlight how linear movement patterns reduce cognitive load and enhance wayfinding, which aligns with later experimental tests measuring user navigation and perception in varied residential layouts. By integrating these case studies into the discussion, this study establishes a theoretical foundation for evaluating spatial legibility in contemporary residential designs.

1.2.3. Colour and Contrast

The appropriate use of colour and contrast can significantly enhance spatial legibility. Colour plays a crucial role in shaping architectural and urban space, as it significantly affects the observer’s perception and experience, while also being challenging to predict in terms of aesthetics, cognitive impact, and behavioural influence [28]. A clear differentiation between walls, floors, doors, and other architectural elements facilitates navigation within a space. The contrast between colours and design elements helps to clearly define different zones or functional areas within a residential space. Perceived colourfulness is highly correlated with perceived clarity and complexity, suggesting that the visual legibility of space is influenced by both the complexity of spatial elements and their chromatic properties [29]. Findings indicate that the spatial application of colour combinations can influence not only perceived luxury but also the preference to stay in a space, with contrast among colours playing a more significant role than extreme or minimal contrast. This suggests that the strategic use of colour relationships contributes to the overall legibility and usability of a space [30]. For instance, the application of warm colours in social areas and cool colours in private spaces can intuitively suggest to visitors both the intended use of the environment and the specific zone in which they are located (Figure 4). The selected case studies, Casa Luis Barragán in Mexico City and the Upper Eastside project in Berlin, serve as well-documented examples where colour application has been deliberately used to influence spatial perception. In Casa Luis Barragán, the strategic use of vibrant hues defines spatial boundaries and guides movement, aligning with the principle that colour differentiation can enhance wayfinding. Similarly, the Upper Eastside project employs a monochromatic contrast to establish clarity and distinguish between circulation paths and functional areas. These examples were chosen due to their demonstrated effectiveness in shaping spatial experiences through colour, reinforcing the theoretical principles outlined in this section. Hidayetoğlu, Yıldırım, and Akalın argue that warm colours can be effectively used as reference points for wayfinding and spatial orientation, while lighter interior tones positively influence spatial legibility and ease of navigation [31].

In the context of urban landscapes, Romina Khalili outlines four principles on how colour application can enhance spatial legibility: (1) using colours to indicate pathways, (2) assigning a distinct colour identity to each district to differentiate them, (3) appropriately colouring urban elements and façades, and (4) enabling the recognition of spatial functions based on the applied colour spectrum [32]. Although this example falls outside the primary scope of this research, as it pertains to urban spaces, it can be analogously applied to residential environments to improve spatial legibility:

• Using colours as wayfinding indicators—Different colours can be employed to mark specific circulation routes. For example, lighter hues may indicate main pathways or corridors, while darker tones can signal less frequently used or more private areas;
• Assigning a distinct colour identity to each area—Each room can have a characteristic colour, establishing a visual identity. This approach helps define spatial boundaries and aids in orientation. For instance, living rooms may feature warm tones, while bedrooms may incorporate more subdued and calming hues;
• Appropriate colouring of elements and surfaces—Painting key architectural elements such as doors, windows, or structural details can enhance their visibility, making them easier to identify and comprehend;
• Recognising spatial function based on the applied colour spectrum—The combination of specific colours with designated functional areas can improve spatial legibility. For example, a kitchen area may feature a different colour scheme than a workspace or a bedroom, reinforcing its distinct purpose.

Through the analysis of key principles influencing the legibility of residential spaces, three parameters emerge as requiring further investigation to more precisely determine their impact on spatial perception and functionality. The first parameter concerns the regularity of spatial structure and movement paths, necessitating further analysis to assess the extent to which clearly defined routes and spatial organisation contribute to users’ ease of orientation. The second parameter pertains to colour, where future research should explore how the presence of vivid colours and contrasts can enhance visual perception and spatial legibility. The third parameter relates to lighting, specifically the role of natural and artificial light in shaping a clear and comprehensible environment.

1.2.4. Lighting

The quality of lighting within a room is crucial for the clarity and visibility of the space, which can significantly facilitate users’ navigation within it. Rooms illuminated by natural light are generally more pleasant to inhabit and provide better visibility within the space. This not only enhances the quality of the environment but also contributes to improved spatial orientation and legibility, as it enables the clear recognition of colours, shapes, and details [33]. Properly positioned lighting plays a significant role in spatial orientation. It can serve as points of reference, particularly during the night. The use of light points or strips along corridors can help individuals follow the flow of the space and more easily orient themselves within the various areas of the flat [31]. Furthermore, clear lighting at the entrance of a room can assist in the immediate identification of rooms and their respective purposes. It is particularly important to highlight the lighting of key points or zones within the flat, such as the kitchen island, dining table, or living room. Such lighting emphasis helps guests and residents quickly orient themselves and recognise the main functional zones of the flat, thereby facilitating movement and use of the space (Figure 5).

Examples that adequately illustrate this statement include the Breeze House in Castellón (Fran Silvestre Arquitectos, 2017) and the house in Melides (Grândola, Pedro Reis Arquitecto, 2007) illustrated above. In both cases, the use of a light strip with artificial lighting within the interior contributes to easier spatial orientation. Its position is easily memorable and helps to clearly define the relative positions of surrounding rooms and objects in relation to its direction, as they can be situated on either side of the light line. While theoretical considerations and architectural examples suggest that lighting should enhance spatial legibility, our experimental findings indicate that lighting did not have a significant impact on perceived legibility.

1.3. Expertise

Research on expertise in design suggests that experts in architecture and design differ from non-experts not only in terms of greater experience and the number of analysed examples but also in their strategic approach to problem-solving. Experts employ top-down and breadth-first methods, while non-experts approach problems sequentially and with a narrower focus. Successful designers are distinguished by their ability to abstract and define problems in ways that lead to innovative solutions [34]. A study by Tanner and Landay indicates that while design non-experts have limited experience and less confidence in creating good designs, they are still notably capable of recognising quality design [35]. Experts, however, achieve a slightly higher accuracy in evaluation (81.2%) compared to non-experts (76.5%). Differences in aesthetic ratings of designs and the methods of comparison affect the precision of the evaluation. Research by Weinberger et al. shows that experts in architecture and design have different aesthetic responses compared to non-experts [36]. Their assessment of spatial coherence is more strongly associated with fascination and a sense of pleasantness, suggesting that expertise shapes how built and natural environments are perceived and evaluated. The research of Usman and colleagues found that although experts assess spatial accessibility and organisation better than non-experts, even they encounter difficulties in understanding the visual aspects of architectural design when using only 2D drawings, while virtual reality proves to be the most effective mode of perceiving spatial characteristics [37]. A study by Marković and Alfirević demonstrates that architects and non-architects perceive architectural expressiveness differently, with architects perceiving minimalist objects as aesthetically superior and less aggressive. This supports the process fluency model—experts process expressive information from simple forms more easily, leading to more positive reactions [38]. In a later study, Marković et al. suggest that while both experts and non-experts in architecture share similar perceptual experiences of architectural objects, experts rely on deeper cognitive processes to evaluate aesthetic and functional aspects, whereas non-experts more heavily depend on immediate visual impressions [39].

These studies suggest that experts in architecture and design differ from non-experts not only in their experience but also in their strategic approach to problem-solving, their ability to abstract, and their capacity to recognise the quality of design. While experts employ more complex analysis methods and achieve greater evaluation accuracy, novices are still capable of recognising good design to a significant degree. Moreover, experts’ perception of space is more strongly linked to aesthetic experience and a sense of coherence, although they too may face challenges in understanding the visual aspects of architecture when limited to 2D representations. Virtual reality has emerged as a more effective method for perceiving spatial characteristics. Given these differences, our experimental methodology considers expertise as a key variable, comparing expert and non-expert participants in their ability to assess spatial legibility and design quality. By integrating these theoretical insights, we aim to investigate how expertise influences the cognitive processing of architectural spaces and whether expert strategies lead to different evaluation outcomes in experimental conditions.

1.4. Hypotheses

Hypothesis 1. 

Experts will be better at recognising and evaluating the legibility of residential spaces.

It is expected that participants with experience in architecture and interior design (experts) will demonstrate a better ability to recognise spatial organisation and assess the legibility of space compared to non-experts. Previous research suggests that expertise in architecture enables better spatial orientation, as well as faster and more accurate perception of spatial relationships, given that architects are trained to analyse the visual and functional aspects of spaces [34,36,37].

Hypothesis 2. 

Regular spaces and movement lines will be more legible than irregular ones.

We expect that spaces with a regular room layout and clearly defined, orthogonal movement lines/paths will be rated as more legible compared to spaces with irregular configurations and complex movement paths. Research has shown that spatial orientation improves when the floor plan is simple and logical, with fewer decision points and clear visual movement paths [12,13,15].

Hypothesis 3. 

More intense colours will contribute to a better legibility and recognition of a space.

It is expected that, compared to pastel ones, more colourful interiors will enable participants to more easily recognise and differentiate various spatial zones. Previous research indicates that colours can serve as landmarks and improve navigation within a space, especially when used to differentiate functional areas [31,32].

Hypothesis 4. 

Focused lighting will contribute to a better legibility and recognition of a space.

This hypothesis predicts that spaces with directed, focused lighting will be rated as more legible compared to spaces with diffuse lighting. Focused light can act as a guide through the space and contribute to better perception of different interior zones [31,33].

1.5. Research Aims/Objectives

In order to test the proposed hypotheses, an experimental study examining the impact of various spatial characteristics on the effectiveness of recognising interiors and the experience of legibility was conducted. Factors such as the regularity of room layouts, movement flow, colour, and lighting were analysed. Additionally, we sought to investigate the effect of observers’ professional training, specifically the role of expertise in architecture and interior design, on the dependent variables—space recognition and legibility assessment.

2. Materials and Methods

Research Methodology

Participants: This study involved 200 participants (84 male, 115 female, and 1 non-binary; average age 36.8 years). Based on expertise, the participants were divided into two groups. The first group (E) consisted of 92 experts, i.e., participants with experience in architecture or interior design (professional architects and interior designers, as well as students of these programmes). The second group (NE) consisted of 108 non-experts, i.e., participants without professional or educational experience in architecture or interior design. The participants were further divided into 4 subgroups—Interiors 1a, 1b, 1c, and 1d—based on the type of stimulus they assessed (see later description of the stimuli). The structure of participants based on expertise in these subgroups was as follows: 1a: E = 24, NE = 32 (total 56); 1b: E = 22, NE = 26 (total 48); 1c: E = 23, NE = 29 (total 52); 1d: E = 23, NE = 21 (total 44).

Stimuli: This study used animations that depicted a virtual “walk-through” or “passage” through the interiors of residential spaces. Since one of the research objectives was to examine the effect of structural regularity on the legibility of the interior, two basic versions of the interior were created: Interior A had a regular structure, with orthogonal rooms and movement lines, while Interior B had an irregular structure, with irregular rooms and movement paths. The plans of these spaces, as well as frames from their animations, can be seen in Figure 6. The “passage” through these spaces was animated so that the participant viewed the interiors from a subjective perspective (the viewpoint was set at 160 cm above the floor). The models of the residential spaces were created using the AutoCAD application, while the surface materialisation, lighting simulation, and animation were performed using Lumion software.

Since one of the objectives of this study was to explore the effects of colour intensity and lighting on interior legibility, four variants of Interiors A and B were created: 1a—colourful focused lighting; 1b—colourful diffuse lighting; 2a—pastel focused lighting; and 2b—pastel diffuse lighting (see examples for Interior A in Figure 7). For corresponding animations, see Supplementary Materials: Animation S1 (A1a), Animation S2 (A1b), Animation S3 (A2a), Animation S4 (A2b), Animation S5 (B1a), Animation S6 (B1b), Animation S7 (B2a), and Animation S8 (B2b).

Design: A four-way mixed design was used. The between-subjects factors were Expertise (E, NE), Colour (colourful, pastel), and Lighting (focused, diffuse), while the within-subjects factor was Regularity (regular, irregular). The dependent variables were the accuracy of recognising the interior based on the floor plan and the subjective experience of legibility, which was measured using six bipolar seven-point rating scales: comfortable–uncomfortable, clear–unclear, simple–complex, organised–disorganised, and open–cramped.

Procedure: This study was conducted online via a Google Form questionnaire. Ethical approval for the study was obtained from the Faculty of Philosophy at the University of Belgrade. There were four questionnaires, one for each group of participants. Each group contained both A and B stimuli at one level of colour and lighting: 1a in the first group, 1b in the second group, 2a in the third group, and 2b in the fourth group (see the Stimuli section). After reading the instructions and providing basic demographic information (gender, age, and expertise), participants proceeded with the task. The work was anonymous, so participants were not asked to give their names. After clicking on the link, the first interior animation (A) opened, followed by questions. The first question asked about identifying the floor plan corresponding to the observed interior—four plans were presented (see Figure 8), and participants had to click on the plan they considered appropriate.

The apartment layouts presented in Figure 8 were carefully selected to reflect variations in spatial configuration, circulation patterns, and functional zoning, which are critical for assessing spatial legibility. These layouts were designed to test the hypotheses regarding how different interior organisations influence participants’ ability to recognise and evaluate spatial arrangements. By comparing responses across these layouts, we aimed to determine whether specific configurations enhance or hinder spatial understanding.

The second section of the questionnaire involved ratings of the interior on six bipolar seven-point scales: comfortable–uncomfortable, clear–unclear, simple–complex, organised–disorganised, and open–cramped. After assessing Interior A, participants proceeded to Interior B (the tasks were identical).

3. Results

3.1. Recognition of 3-D Dynamic Representations of Interiors on 2-D Plans

The accuracy of recognising dynamically displayed 3-D interiors in 2-D plans was a direct perceptual–cognitive measure of legibility—the more accurate the recognition, the greater the legibility (examples of 3-D spaces and 2-D plans can be seen in the Stimuli and Procedure sections). For each interior, the proportion of correct recognitions of each interior was obtained, and these measures were included in analyses of variance to determine the dependence of recognition accuracy on the four experimental factors—expertise, regularity, colour, and lighting.

A four-way ANOVA with the between-subjects factors Expertise, Colour, and Lighting and the within-subjects factor Regularity revealed the following outcomes:

• Expertise: Experts recognise interiors more accurately than non-experts, F(1,199) = 34.45, p < .001. The effect size was large, η² = 0.170 (see Figure 9: Graph 1 and Graph 3).
• Regularity: Regular interiors are recognised more accurately than irregular ones, F = 15.27, p < 0.001. This effect was of medium size, η² = 0.074 (see Figure 9: Graphs 1, 2, 3, and 4).
  • An interaction was obtained between Expertise and Regularity, F = 10.20, p < 0.002, with a small effect size η² = 0.050. This interaction arises from the fact that the regularity of a structure has no effect on experts, whereas irregular structures significantly hinder recognition among non-experts (see Figure 9: Graph 1).
• Colour: More intense colours contribute to a better recognition of interiors compared to pastel colours, F = 13.06, p < 0.001. The effect size is medium, η² = 0.064 (see Figure 9: Graph 2).
  • An interaction was identified between Expertise and Colour, F = 6.16, p < 0.02, with a small effect size η² = 0.031. This interaction suggests that pastel colours significantly hinder recognition among non-experts, while this effect is absent among experts (see Figure 9: Graph 3).
• Lighting: This factor has no significant effect on recognition (see Figure 9: Graph 4).
• Other interactions, aside from the two mentioned, were not significant.

3.2. Legibility of 3-D Dynamic Representations of Interiors

In this part of the research, we examined the effects of expertise, regularity, colour, and light on the subjective assessment of legibility. Since we had six scales on which participants assessed legibility, the first analysis aimed to specify whether all these scales measure the same thing—legibility—or whether they represent different experiences. For this purpose, we performed a principal component analysis on the inter-correlations of assessments on six scales.

Principal component analysis demonstrated that assessments across the six legibility scales for both interiors are organised into a single principal component (see

Table 1. First principal components extracted from the assessment of two interiors. The percentages of variance explained by the first principal components, as well as the loadings of the 6 scales, are presented.

	Interior 1 49.38%	Interior 2 58.27%
Comfortable	0.692	0.850
Clear	0.786	0.844
Simple	0.604	0.546
Organised	0.754	0.786
Arranged	0.777	0.817
Open	0.575	0.692

). No rotations were performed, as no additional significant components were extracted.

Further variance analysis was conducted based on a single measure of legibility, which represents the mean of assessments across the six scales (see graphs in Figure 10).

A four-way ANOVA with the between-subjects factors Expertise, Colour, and Lighting and the within-subjects factor Regularity (of structure) revealed the following findings:

• Between-subjects factors did not exert significant effects on legibility assessments.
• The only significant factor was the repeated factor of Regularity: regular interiors were rated as more legible than irregular ones, F = 179.55, p < 0.001. The effect size was large, η² = 0.483 (see Figure 10: Graphs 5, 6, and 7).
• An interaction was found between Regularity and Lighting, F = 10.20, p < 0.05, although the effect size was small, η² = 0.021. The difference causing this interaction arises from the varying effects of lighting on irregular interiors, such that interiors with lower lighting are less legible than those with higher lighting (see Figure 10: Graph 7). This finding is particularly interesting for the analysis of the specificity of the relationship between regularity and illumination. On the one hand, regular interiors are already legible enough so that either the positive effects of focused lighting or the negative effects of diffuse lighting on legibility could not be manifested. However, on the other hand, when the interior is irregular, then the lighting has its chance to act—focused light improves legibility or, complementarily, diffused light lowers legibility.
• Other interactions, aside from the mentioned one, were not significant.

4. Discussion

The research results generally confirm the established hypotheses, while simultaneously raising new questions regarding the influence of individual factors on the legibility of residential spaces. The first finding, which aligns with the expectations, pertains to the difference between experts and non-experts. Architects were more accurate in assessing the legibility of spaces compared to non-architects, which is consistent with previous research on expertise in design [35,36]. This outcome can be explained by the fact that experts employ more complex cognitive strategies and rely on experiential knowledge when analysing spatial relationships.

Moreover, it was indicated that more orderly spatial arrangements facilitate greater interior legibility, which is in line with earlier findings about the ease of recognising spaces when the organisation and movement paths are logical and consistent [13]. On the other hand, one of the unexpected findings relates to the absence of an effect of lighting on spatial legibility. While previous research suggests that lighting enhances spatial perception and navigation, the present findings indicate that its effect may depend on additional moderating factors. Specifically, the interaction between lighting and regularity implies that lighting does not independently improve legibility but may amplify the existing clarity of structured environments or worsen the ambiguity of irregular spaces. This suggests that diffuse lighting in irregular settings might contribute to perceptual uncertainty, whereas regular layouts provide sufficient structural clarity that minimises the role of lighting. This discrepancy suggests that additional factors, such as users’ familiarity with the space, contrast levels, or individual perceptual differences, may play a more prominent role than previously assumed. Further research is necessary to clarify these relationships and better understand the conditions under which lighting contributes to spatial legibility. It is possible that the intensity of artificial lighting in the animation was not sufficient to produce significant differences in spatial perception, or that lighting has a more complex relationship with other factors, such as contrast and colour, which may have obscured its impact.

Of particular interest is the finding regarding the interaction between expertise and colour. While pastel colours significantly hinder the recognition of interiors among non-architects, architects show no particular effect of colour on legibility assessment (see Graph 3). This suggests that non-experts rely more on colour cues for spatial recognition, whereas experts depend primarily on spatial configuration and organisation. The fact that experts are unaffected by colour variation aligns with previous findings that their cognitive processing is more attuned to structural and functional aspects rather than surface-level features. This may indicate that architects predominantly rely on the perception of spatial arrangement and organisation, whereas non-architects use colour as a visual cue in recognising interiors. This result further supports the thesis that experts process visual information differently from laypersons, which may be significant for further research in the field of spatial perception and architectural cognition.

When comparing the contributions of individual factors based on the magnitude of their effects (see partial eta squared, η²), we can make the following conclusions: The greatest effect on the accuracy of interior recognition is attributed to (1) expertise, as a characteristic of the respondents (experts perform better in recognition than non-experts), followed by (2) the regularity of spatial structure as a stimulus factor, (3) colour, and, finally, (4) lighting, which has no significant effect on recognition. The importance of expertise also manifests in its ability to render the observer resistant to various distracting stimulus factors. Specifically, respondents with professional and/or educational experience in architecture and/or interior design will accurately recognise interiors based on 2D plans, regardless of their regularity or the colour marking of key details (see Graph 1 and Graph 3).

5. Conclusions

The research analysed key principles of the legibility of residential spaces, highlighting their significance for the functionality, safety, and efficiency of interior organisation. The results confirm that factors such as the proper arrangement of rooms, clear lines of movement, colours, contrasts, and lighting significantly affect the ease of navigation within the space and its perception.

The theoretical contribution of the work lies in the systematisation of principles that determine the legibility of space, thus filling a research gap in architecture and interior design. The empirical part of this research study provides insight into user perception, emphasising the importance of subjective and objective parameters in defining the legibility of space.

The practical implications of this work are manifold—architects, interior designers, and urban planners can use the results as guidelines for designing living spaces that are intuitive to use and customised to residents’ needs. Specifically, the findings suggest that prioritising spatial regularity and clear movement paths enhances interior legibility, while the role of lighting should be carefully considered in relation to contrast and layout complexity. Design strategies that integrate structured spatial organisation with optimised lighting and colour schemes can improve user experience and wayfinding in residential environments. Furthermore, the results indicate that expert users process spatial information differently than non-experts, suggesting that residential spaces should balance intuitive design features for general users while still accommodating expert-level spatial interpretation needs. The importance of a simple and logical spatial organisation is particularly emphasised, as it allows for better use of resources and improves the quality of living.

Future research could expand to various typologies of living spaces, including apartments of different sizes and contexts of individual and collective living. Additionally, future studies should directly investigate the unexpected findings regarding the interaction between lighting and regularity, as well as expertise and colour perception. Examining how lighting conditions influence spatial cognition in more diverse environments, or testing the role of contrast more systematically, could offer deeper insights into these complex relationships. Conducting further experiments with expert and non-expert respondents across varied residential settings will also contribute to refining design principles for optimal spatial legibility and could deepen the understanding of both subjective and objective legibility of space.