An Accessible Smartphone Interface Design Computer Science Essay

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As mobile technology becomes increasingly adaptive and ubiquitous, users have more opportunities to access materials and complete activities that were extremely difficult or impossible before. Mobile phone technology, specifically smartphone technology, has evolved at a tremendous rate, moving toward a multi-functional device with advanced capabilities including digital camera, MP3 player, Wi-Fi, built-in keyboard, complete operating system software, and abundant memory, accommodating communication, entertainment and professional work. A market share study of the U.S. mobile phone industry [1] estimated that, on average, 42.7 million people in the U.S. owned smartphones at the end of 2009. Mobile phones play a role in the "micro-coordination" of everyday life, creating a sense of security for the individual [2].

However, is this type of computing device universally accessible? Unfortunately this type of computing device is still mainly inaccessible to individuals with visual impairments [3] or an upper extremity disability due in part to the challenges and demanding usage of mobile devices. For these individuals, accessibility of mobile communication does not simply mean keeping connected with others, it also enables them to lead more secure and autonomous lives. because individuals with disabilities desire to be socially independent and "a valued part of society" [4]. Individuals with visual impairments, who are restricted from visualizing the interface, and individuals with upper extremity disabilities, who have limited operation capabilities of handheld devices, are two of the most challenged user groups for mobile phone usage and mobile technology adoption. The lack of accessibility in current handheld devices undermines access to the benefits of mobile handheld communication technologies. According to the World Health Organization (WHO, 2009), it is estimated that about 314 million people worldwide have visual impairments and 45 million of them are blind. Other data show that 8.2 percent of the world population aged 15 and older have limitations with upper body mobility and functioning [5]. Thus, these users are a significant portion of the population yet they continue to be marginalized in technology design research and development.

Although there is a growing body of literature describing the current problems encountered by users with visual impairments [3,6], users who are blind [7], and individuals with upper extremity disabilities, the studies focus on navigation and way-finding systems that use mobile devices to address corresponding problems. Few studies have looked into and investigated the needs and desires of users with visual impairments and those with upper extremity limitations regarding requirements of smartphone technology. Furthermore, no comprehensive agreement has been reached in terms of accessible mobile phone interface design guidelines, particularly accessibility principles. To compound the challenge of a lack of academic research, the mainstream market has not yet fully considered satisfying the needs and demands of individuals with such disabilities when designing devices for common use. As technology continues to advance, the range of population that encounters accessibility problems extends beyond the population of users with disabilities or the elderly. Designing for universal access will allow for adapting to diversity in the characteristics of the target user population, in the scope and nature of tasks, and in the different contexts of use and its effects [8,9].

2 Purpose

According to Thayer and Thayer [10], requirements elicitation is a process through which developers discover, review, articulate, and understand users' needs and the constraints on the software and development. However, it remains difficult to collect information through direct communication between users and designers. Finding a more effective way of identifying user requirements and generating corresponding design guidelines is necessary for reducing the gap between a designer's conceptual model and a user's mental model of the design. To address this problem, we propose a method for reviewing existing design guidelines, validating them with user input, and developing a heuristic checklist for use by the designers of mobile devices to achieve good product accessibility. Heuristic checklists are particularly useful for consumer products with a relatively short development phase and a competitive market [11].

3 Background

3.1 Accessibility and Accessible Design

Generally, accessibility refers to the extent to which a product or service is available to as many users as possible [12]. IBM researchers [13] distinguished two key aspects of accessibility: (1) technical accessibility, which refers to the adoption of accessibility practice into design to ensure the assistive technology's usefulness and (2) usable accessibility, which refers to the application of related usability principles for the benefit of people with disabilities. Accessibility relates to physical access to equipment as well as the operational suitability of both hardware and software for any potential user [14]. Most individuals with disabilities have been excluded from either one or both of these aspects with current mobile phone designs, therefore there is a need to focus on usable accessibility of both the operational hardware and software.

With information and communication services, Shneiderman [15] specified accessibility as "universal usability", having more than 90% of all households as successful users of these services at least once a week. As he pointed out, challenges in attaining "universal usability" for web-based services include technology variety, user diversity (accommodating users with different skills, knowledge, age, handicaps, literacy, culture, etc.), and gaps in user knowledge. Two major ways to support accessibility are "universal design" and "assistive technology" [16,17]. Universal design, also called accessible design, inclusive design or design-for-all, refers to the design of products to be usable by all people, to the greatest extent possible, without the need for specialized adaptation [17]. Benyon et al. stressed that the term universal design does not mean one design, but design to be usable by all [14]. The incorporation of assistive technologies allows users with special needs to perform functions that might otherwise be difficult or impossible, bridging the gap between people with disabilities and the device interface. Once people can access a system or service, usability then refers to the quality of interaction, indicated by key parameters, such as the success rate or completion time of a task or the number of errors made [8].

3.2 Accessibility Applications

An increasing number of alternatives of information presentation are now available to aide in greater accessibility for people with disabilities, including audio or tactile presentation of textual, mathematical and graphical information [18]. Software developers continue to improve web accessibility by developing assistive technology to help with daily usage of the web [19] and the World Wide Web Consortium has suggested various design guidelines to make websites more accessible [20]. Accordingly, an increasing number of accessibility standards and guidelines have appeared in order to provide better and greater accessibility, such as in terms of software accessibility, web content accessibility, and media accessibility [21].

Despite the growing popularity of the mobile phone, few studies have focused on the requirements for accessible small-screen handheld mobile devices, such as a smart phone or personal digital assistant (PDA), for users with disabilities. There are significantly fewer studies than those conducted on web site interface design. In a review of accessibility research regarding handheld mobile phones and applications (software systems operating on mobile devices) [22], a multi-modal approach using haptic and auditory output was promoted. Well-designed multi-modal applications could benefit users with various disabilities [12]; specifically, this design approach provides users with visual impairments with more mobility and orientation information in order to guarantee a fully social inclusion in their daily life. Examples of the application of multi-modal design include the use of vibrotactile outputs in mobile guides, developed for users with visual impairments in museum environments to enhance orientation and obstacle avoidance [12]. In addition, tactons, structured vibrotactile messages that utilize studied parameters like rhythm, roughness, intensity, frequency, and spatial location have been incorporated into many new devices [23]. The use of audio output combined with other applications, such as RFID and electronic markers, has been advocated and has enabled guidance systems installed on mobile phones or handheld computers to support users with visual impairments for in-door orientation and mobility solutions [24]. For these relatively new media, technology, and new forms of applications, actionable guidelines and standards are not as comprehensive as those for web accessibility.

3.3 Mobile Phone Usage Characteristics of Users with Visual Impairment

In addition to having an understanding of accessibility and accessible design of mobile phones, knowing the characteristics of users with visual impairments is necessary for predicting and designing for their interaction with mobile devices. There is no easy way to characterize a representative user with visual impairment, although it is necessary for the implementation of user-centered design. Among the population of users with visual impairments, some may have be born with severe visual impairment, which means that they have limited experience of or interaction with the sighted world, while others may become impaired through illness or accidental causes later in life. Therefore their mental models may be quite different with each other, which is also distinct from users without visual impairments as well. In the past, and among the older population, users with severe visual impairments have had mobile phones solely for the purpose of making phone calls either if away from home or if calling for help [6]. The most commonly chosen phones have historically been those that were simple to use and had buttons that could be easily distinguished [3]. Touchscreens have become more popular in mobile device design, but many users with visual impairments have expressed a preference for buttons that provide tactile feedback and location awareness [25]. In contrast, among a small sample of younger blind users (average age = 31.4 years), researchers found that all of their participants used numerous mobile devices, including either a smart phone or PDA, for making phone calls, playing music, listening to audiobooks, and using the calendar [7,26]. Although many of these tasks are performed regularly, the users still expressed accessibility problems while operating their mobile devices [26]. While they may not have previously had the ability to use many of these functions, users with severe visual impairments desire access to the advanced mobile device functions.

Even for sighted users, challenges and limitations to mobile device usage include, but are not limited to, the small screen size and data entry methods [22]. Individual differences, such as spatial and memory abilities, subjective confidence, and mobile phone expertise [27], could also be factors that influence the perceived accessibility of mobile phones, a topic which is not discussed in detail here since it is beyond the scope of this study and would need further exploration. It should be noted, however, that any improvements on accessible design could eventually benefit users without disabilities as well.

4 Overview of the Methodology

Phase 1: Design and Development of User Requirements Using Participatory Design Method

Upon a comprehensive review of the literature on standards, guidelines, and user requirements regarding mobile handheld device accessibility, a set of preliminary user requirements relating to accessible touchscreen phone design was extracted, filtered using participatory design and then integrated and transcribed to create an operational version of design guidelines.

Phase 2: Application of Design Guidelines in a Case Study

Phase 2 included two sub-sections, heuristic evaluation and usability testing, where the set of guidelines were applied on high-fidelity prototypes produced by a commercial manufacturer. The objective was two-fold: to examine whether the prototypes fulfill end-users' needs and desires for a touchscreen phone by applying the set of elicited user requirements as a criterion and to identify a set of user requirements based on a more realistic experience.

Phase 3: Configuration of User Requirements into Accessibility Heuristics

The purpose of Phase 3 was to configure the identified user requirements into a set of heuristics for designing touchscreen phones and that could be generalized to accessible mobile or touchscreen devices.

A diagram depicting the described phases of this study is presented in .

Fig. Method overview

5 Phase 1: Design and Development of User Requirements

Initially, a list of accessibility requirements was developed based on a review of a set of selected sources. According to Demirkan [28], the designer's knowledge is not only drawn from relevant media (e.g., books, journals and trade magazines) and the relevant domain (e.g., observed cases from another source or experience of the designer), but also from users and experts in the relevant community, the third source of knowledge. Thus, a participatory design session was held to capture user requirements from experts.

The literature on human computer interaction (HCI) provides little help in the selection of usability constructs and key parameters [29], particularly in the accessibility domain, as there is no standardized definition concerning accessibility. McGee et al. [30] conducted a study to determine how users rate 64 potential usability measures using an usability concept survey (UCS) and arrived at five main groupings, including core usability (e.g., efficiency and ease-of-use), secondary usability (e.g., effectiveness and accessibility), and satisfaction quality. Recent studies have shown that many of the usability factors, such as effectiveness, efficiency, and satisfaction, are independent or weakly correlated [29,31,32]. The weak correlations have prompted researchers to use a composite usability measure to estimate overall usability by using one or two usability aspects, but this could lead to unreliable conclusions about overall usability [31,29]. Dumas and Redish [33] have suggested that it is important to consider the current product development phase, for example, when testing prototypes, performance measures, such as timing, might not be appropriate. Based on synthesizing the user requirements regarding accessible features from the literature, three evaluation attributes were identified: 1) accessibility; 2) ease-of-use; and 3) effectiveness. Accessibility was used to measure the members' agreement on design guideline items to examine whether the guidelines accurately addressed their needs and desires.

After defining the constructs and determining the user requirements from the literature, a five-point Likert-scale questionnaire was developed with anchors ranging from strongly disagree (1) to strongly agree (5). During the study, PD members were asked to rate the elicited user requirements against three statements corresponding to the three constructs: 1) making the phone more accessible; 2) making tasks easier to perform; and 3) making the phone more effective to complete tasks. These statements were used to identify the degree of agreement among the PD members as to whether the user requirements matched their perspectives of a phone being accessible, easy of use, and effective. Sample statements are:

1a. Users must have "Power" and "Menu" keys that are separated from the keypad. Indicate how well this feature makes the phone easy to access.

1b. Users must have "Power" and "Menu" keys that are separated from the keypad. Indicate how well this feature makes tasks easy to perform.

1c.Users must have "Power" and "Menu" keys that are separated from the keypad. Indicate how effective this design feature is to help to complete tasks.

5.1 Early User Involvement Methods and Participatory Design

Since the introduction of user-centered design by Gould and Lewis [34], the HCI community has adopted this approach for developing usable systems. Among these principles, the first principle is early focus on users and tasks, which has long been emphasized in the system development process, and it is recommended that design teams be brought into direct contact with potential users [34]. End-users should be involved throughout the systems development life cycle [35] involving user in an early phase of system development is useful even in a short time frame, in terms of improving usability of the product and increasing customer satisfaction [36].

Participatory design (PD) was used throughout this study as a user involvement method to bring together the researchers and potential users. PD emerged in 1980s and has since been discussed and applied widely in the areas of technical communications [37], human computer interaction, computer support cooperative work, information system design, product design [38], and interface design [39]. PD is defined as a set of theories, practices, and studies related to end users [40], which brings researchers/designers and end users together into the process of development [41] and attempts to bring together the participants' implicit, invisible and holistic knowledge they might not be able to articulate and the researchers' more analytical knowledge [37]. Muller [40] proposed that most traditional design methods are relatively one-directional, with designers typically analyzing requirements articulated by users, delivering a system to the users, and then running usability tests. Contrary to this, participatory design supports two-way design process, tying the designers and users together [40].

5.2 Participants

In this study, individuals having either severe visual impairments (SVIs) or upper extremity disabilities were recruited. In this paper, the term individuals with SVIs refers to individuals having a visual acuity of 20/400 or worse in each eye that cannot be overcome with corrective lenses and individuals with upper extremity disability refers to individuals with loss of function in one or both hands (manual dexterity disability).

The criteria for participation included not currently owning a smartphone, but having a cell phone that they used regularly. In total, approximately 13 participants were screened to determine eligibility. Of those, four were selected to join the PD team and complete the initial evaluation of the user requirements. The other participants were excluded because either they did not meet the visual acuity requirements or they did not regularly use a cell phone. During the process of developing user requirements through PD meetings, a possible age effect of generation on preferences for specific requirements was identified (qualitatively shown in ). Thus, after the second round of ratings, two additional participants were recruited to have relatively balanced age demographics in the small number of PD members. Thus, six participants took part in this study, five having SVIs and one having an upper-extremity disability. summarizes the demographics of all six PD members.

Table Demographic information of PD members






















Disability Type

No vision

20/800 Snellen

No vision

Partial Quadriplegia

20/800 Snellen

20/500 Snellen

Years of Experience







Phone Type







5.3 Procedures

This research began by eliciting the needs of users with SVIs and users with upper limb limitation on mobile devices through investigating empirical literature. An extensive literature review was conducted on U.S. mandatory standards, standards from other countries that are either mandatory or strongly encouraged, and voluntary standards. In addition, the set of user requirements, shown in , was also derived from a review of the accessibility features and functionality of phones produced by the Apple Corporation, Nokia, and Research-In-Motion (RIM, Blackberry), and from trade magazines and research publications.

During the first meeting of the PD team, demographic information of the PD members was gathered and then the purpose of the project was explained. All participants were given copies of the informed consent form and had the opportunity to hear the information read aloud. After all procedural questions were answered, participants were escorted to separate rooms and assigned to one of the four researchers to evaluate the user requirements. This method was used to ensure the PD members provided independent ratings. Researchers remained with the participants in case there were questions or to rephrase the guidelines as needed. The user requirements were rated (using a 5-point scale) by all PD members with respect to accessibility, ease-of-use, and effectiveness as described above. The rating sheet was administered in Braille and large print format and the participants were given the definitions of each rating anchor. The rating task was completed in about 30 minutes, after which, the PD team members were brought back together to discuss their ratings and provide feedback. They also gave comments on each category of the user requirements taxonomy. The session lasted two hours.

A criterion was set such that guidelines rated as 4 or 5 with high agreement among 3 or 4 team members were automatically included in the heuristic checklist. Then the second set of guidelines was extracted from the remaining user requirements that were not rated with high agreement. All other requirements after the first filtering were independently rated again by the PD members using an online survey. User requirements that did not meet the criteria in the second filtering were excluded and the high agreement items were extracted and combined with those from the first set.

5.4 Results

The initial set consisted of 59 separate requirements, organized into seven general categories. After the first rating stage, the PD team members had high agreement on 42 of the original 59 user requirements. The remaining 17 items were included in the online survey described above and only two of those items then received a high level of agreement from the participants. At the end of the second filtering there were 44 user requirements distributed among the seven categories. The final design guidelines based on the extracted user requirements were compiled and are shown in Appendix A.

5.5 Discussion

The preliminary findings indicated that a few features strongly influence the accessibility of the phone. Having a phone that is shaped to fit the hands and having tactile markers on the surface were considered to be good for accessibility. Incorporating multiple types of media as a means of supporting menu exploration, such as voice activation in addition to the already present visual feedback, were also considered vital. Other features that were rated highly were voice dialing, speed dialing, any-key answer, and the ability to cancel a selection. The PD members indicated that both audio feedback of indicators and vibration features aid with accessibility. It can be seen from the results that short-cut operation, error prevention, and using multiple types of media were considered as three main categories of accessible features to the participatory design team experts.

In terms of mechanical controls, as seen, device shape, materials, and durability were considered as key parameters of hardware features, indicating the mobile device should not require tight grasping or similar interaction that may hinder users operation. Easily detected buttons and functional operations were highlighted in the findings, including designing to help users quickly identify and operate a certain function, with easily detected edges and uniquely shaped and large commonly used buttons with tactile markers. Regarding display design, since visual interface design is not as advantageous to users with SVIs as for sighted users, several key features involving display with high resolution and low reflection as well as highlighted buttons were included. Within speech operation and controls, emphasis was on voice activation to determine system status, operate essential operations, and easily access to screen reader technology. For phone operation, being able to quickly start the phone and answer a phone call were preferred and feedback and error correction were also required. The audio feedback and controls category includes several detailed requirements focused on having screen reader technology and other sound feedback to users as requested. In addition, vibration feedback were included for touch-operated controls.

6 Phase 2: Application of User Requirements

6.1 Employing Heuristic Evaluation in Accessibility Assessment

Heuristic evaluation (HE) was applied to identify accessibility issues relating to studied prototypes. HE has been widely used as an informal usability inspection method, and broadly adopted among usability researchers to evaluate interface design in the field of human computer interaction [42]. For this study, a commercial mobile device manufacturer provided the two prototypes, one featuring voice activation and the other screen reader technology. The heuristic evaluation and formative usability tests considered both hardware and software features and were undertaken to apply the design guidelines developed in Phase 1 to investigate the accessibility related issues of the studied prototypes and to further supplement the identified user requirements.

6.2 Procedures

6.2.1 Hardware evaluation

An individual meeting with each of the six PD members was scheduled. All materials were presented in Braille and large print format. At the start of the session, the prototype smart phone was given to the participant, who was allowed to handle the phone as preferred for about 30 minutes. Participants were allowed to ask questions during this familiarization stage. After exploring the prototypes, participants were asked to rate the prototype hardware against the user requirement heuristics developed in Phase 1 on a scale of one to five, with anchors from "very bad" (1) to "very good" (5). The researchers remained with the participants in case there were questions or if they needed to rephrase the guidelines for clarification. The rating task was completed in about 30 minutes. After completion, the following specific and open-end questions were asked to acquire recommendations and comments:

A) What design features on this phone do you think make it accessible? What do you like about the phone?

B) Can you think of a way to make this phone more accessible based on what you have been able to observe today?

C) How likely are you to use a phone like this? Why?

During the evaluation, participants were able to touch and take actions with the prototype whenever necessary. In total, the session lasted approximately two hours. The meeting was audio-recorded to ensure that the ratings and responses were accurately documented. The participants were compensated for their time.

6.2.2 Software evaluation

After the hardware evaluation was complete a new set of prototypes was received for a heuristic evaluation of the software. The prototypes were distributed to the PD team members and they were able to keep the prototype for three days to allow them time to familiarize themselves with the phone operation. They were provided with a simplified user manual with brief instructions about how to use the main functions. Although the prototype exploration period was three days, the exact time of using prototypes could not be controlled due to most participants working full-time and variation of their willingness. After the three days, the researchers met the with participants individually and asked them to perform eight essential task scenarios that had been developed to be highly dependent on direct manipulation. These tasks were: 1) power on; 2) place and end a call (by entering from start menu, by short cut, and by speed dial; 3) add a contact; 4) send a text message; 5) delete a text message; 6) turn on/off the screen reading software; 7) add an appointment to the calendar; and 8) play media. The participants were asked to perform each task in three minutes after being presented with the scenario. Since the two prototypes had different major features, one with voice activation and the other with screen reading software, the participants completed the tasks on both prototypes and the order of prototype presentation to the participants was counterbalanced.

Success was measured by having the participants verbally articulate that they finished the task. After the whole session, the moderator examined each task participants claimed to have finished to ensure successful completion. Since most tasks could not be completed by participants, task completion time has not been included in this report. Upon task completion, the participants were asked to rate the two prototypes based on the heuristics of the user requirements. The rating sheet was administered in Braille and large print format. The prototype was given to the participant and he/she was allowed to handle the phone as preferred. Participants were allowed to ask questions as well. The rating task was completed in about 30 minutes. After completion, the following specific and open-ended questions were asked in order to acquire recommendations and comments:

A) What design features on this phone do you think make it accessible? What did you like best about software part?

B) Can you think of a way to make this phone more accessible based on what you have been able to observe today?

The whole session was approximately two hours long. The meeting was audio-recorded and videotaped.

6.3 Results and Discussion

provides the summary of the means and standard errors of the prototype hardware and software ratings from the six PD members. In comparing the results of the six raters in pairs, levels of agreement varied from 12.34% to 15.94%. Although agreement is important in most tasks involving independent evaluators, lower levels of agreement were expected because the judges had varying backgrounds and perspectives.

Fig. Ratings of the prototypes' hardware and software accessibility features

The guideline that received the lowest ratings for the hardware evaluation was the presence of tactile markers for primary feedback. The participants felt that the prototype lacked a tactile method for indicating which button they were pressing, especially for soft keys on the front (touchscreen portion) of the phone. The shape of the phone, its thinness and light weight were preferred by all participants. In response to what design features they liked and that made the phone accessible, highlights of the comments included:

The differing shapes, sizes, and textures of the side controls made them easier to distinguish.

Only the most important items have buttons and they are simple buttons.

Having a big screen that is up-to-date is helpful.

The phone can be held in one hand. (user with physical disability)

Having a separate power button is useful.

Having a home key that supports one-step navigation to the main menu was considered useful.

With regard to the prototype software accessibility the category with the lowest rating from the five participants with SVIs was 'Brief sound with selection' (Mean = 1.5, SD = 0.58). The three younger PD members rated the 'Read back of menus' lowest (Mean = 1.33, SD = 0.58). The same two guidelines were also lowest for effectiveness with mean = 1.75 (SD = 0.96) and 1.33 (SD = 0.58), respectively. The users were unsatisfied with how the phone read back the options for the highest-level menus, but then did not read back menus once inside a function, such as the email or calendar. The participants expressed a desire to be able to hear the menu options whenever they are rolled over so that they know what they are selecting. Hearing a sound with each selection is also important for feedback and confirmation of actions. The participants were satisfied with having separate volume control buttons that gave them access to raising or lowering the volume without having to navigate the touchscreen options.

For the software task scenarios, a success rate for each task was calculated. Binary success was used to measure task success; either the participant completed a task successfully or they did not, getting close did not count in this case. Each time users performed a task, they were given a 'success' (1) or 'failure' (0) score. With the numeric score, the average success rate was calculated and these values are shown in .

Fig. Average success rate for tasks completed on prototype with text reader

Within their comments, four out of the six PD members indicated that voice activation provided the most useful functionality while operating the prototype. Large text type and large icons, screen reader technology and sound feedback of phone status were also considered to be useful design features by two of the six participants. Simplified menu, vibration feedback, many functions, buttons on the side and few buttons on the phone were believed to be good design features on both prototypes. When commenting on areas for improvement of the prototypes, 'easy to access phone status/ feedback of current screen' was believed the most needed design improvement. 'Accessible tutorials' and 'more and simpler voice activation command' were considered by two participants as features needed to be added in the next design iteration.

During the course of the three-day familiarization period, interaction with the two prototypes was limited and unpredictable due to the full-time work schedules of most participants. It was expected that both familiarity with the prototypes and subsequently task performance would vary with the amount of time and effort spent by participants during the three days. The results of the software evaluation indicate that discovery of full system potential depended on the participants' active exploration and the accessibility of exploration opportunities with little user instruction. The latter was heavily impacted by and closely tied with the availability of accessible functions and usable features. Therefore, the deficient accessibility features of the touchphone interface made it difficult to explore the prototypes with the optimum level of effectiveness, efficiency and satisfaction. Participants with SVIs can only explore prototypes to a limited level with or without assistance at home.

6.4 Formal Usable Accessibility Test

Several usable accessibility problems were identified based on the user requirements developed and evaluated in the earlier phases. Since the prior results showed low task completion rates, suggesting severe usable accessibility issues involved with the studied prototypes, it was clear that some of the interface design needed to be improved based on the identified heuristics. Usable accessibility testing was undertaken by a set of nine participants with SVIs in a lab setting and task completion, time to completion, and user feedback were recorded and analyzed to generate design specifications and then content analysis methods were used to make the user requirements more complete, thorough, and valid. In this paper, we do not report the results found specific to the prototype, but instead present only the results that can be generalized to the design of most touchscreen mobile devices.

Figure 4 shows the accessibility issues identified during the usability testing. They are presented in the descending order of the number of times they were included among the responses from the nine participants. As shown, the findings indicate that two general types of problems arose. First, there was a lack of feedback indicating the current phone or system status. It is understandable that individuals with SVIs would desire and require an awareness of what is on the screen to allow them to perform the next desired action. Thus, an accessible phone should provide cues to indicate what is on the screen and to guide people without acute visual perception towards wanted features. Second, although control via voice command was considered a very useful feature by users with SVIs, there were several accessibility problems with this function that resulted in a failure of use. Voice commands tend to be developed by software designers based on their mental model, however, this schema may not fit with the users' mental model or the words and commands they would consider using, creating a gap. To reduce such a gap, voice commands should be designed in a more intuitive way to allow people to communicate with the phone without requiring the memorization of certain fixed commands that might increase task difficulty.

Fig. 4 Accessibility issues identified during usability testing

7 Phase 3: From User Requirements to Heuristic Checklist

The purpose of Phase 3 was to configure and integrate the identified set of user requirements into 11 heuristics, shown in Appendix B that could function as a collection of guidelines for designing touchscreen phones with the consideration of individuals with SVIs or upper extremity disabilities. This quick accessibility heuristic checklist serves to help designers and developers, who are not experts in accessibility, when designing such types of products.

8 Limitations

This study presented some issues that can be improved upon in the future in refining the accessibility checklist or adjusting it based on studies to accommodate various user groups and contexts of use. One limitation was the restricted number of participants with physical difficulties as well as those with no apparent disabilities. The PD team members with SVIs that were included in the first meeting were either baby boomers or older. For the subsequent PD sections, two additional Generation Y users were recruited, but the ratings and comments from the first session may have been biased based on the technology exposure and experience of the older user population. Older users in general may also have different smartphone design needs that may be reflected in their responses, but interpreted here as needs for users with SVIs. Although the test sample may not exactly fit the expected user demographic of such phones, if they are designed for a more general population with expanded needs, then they should meet the accessibility needs and expectations of younger users with disabilities. The small number of participants also limited the ability to reach agreement on many of the design comments and suggestions.

An additional limitation of this study is the lack of knowledge of and control over the time each PD team member spent with the prototype prior to the software evaluation. Although each participant was provided with the prototype for three days and they were given an instruction manual, there were varying levels of time spent learning the features and trying to operate the phone. Factors such as work schedules and insufficient help in learning the phone may be justifications, but there may also have been frustration with the new technology that negatively impacted their interest in exploring the design. The researchers had no way of ensuring an equal dedication of time while maintaining the natural learning environment. The hardware and software evaluation comments may also have been biased by the presentation of a specific prototype to the participants. Although they were given the opportunity to express concepts for the design of their ideal smartphone, they may have been influenced by the positive and negative features they found in the current prototype or in their present mobile phone. These questions may have been better asked prior to their evaluation of the prototype, but then they may have been limited by their lack of knowledge and understanding of the potential design features and functions.

9 Conclusions

With the ultimate goal of achieving universal access, this study presented an accessibility heuristic checklist for designing mobile phones for users with visual or upper extremity impairments and discussed how this checklist has been used in identifying accessibility problems on two mobile device prototypes. The findings from the qualitative and quantitative data provided support for a ready-to-use accessibility checklist for designers and developers in the early design phases of new mobile products. The developed accessibility checklist not only provides a useful tool that is relatively thorough and comprehensive, but is also proposes a method that transforms user requirements to design guidelines, then to a practical design tool available for quick use, contributing to the ultimate goal of access for everyone.