Keywords

1 Introduction

With the advent of an aging society, the elderly are receiving much attention. The elderly are facing the threat of physiological deterioration, including impaired perception, motor skills, and cognitive abilities. Physiological deterioration makes it difficult for the elderly to operate or use products. For example, reduced visual acuity prevents the elderly from seeing tiny things [1], and memory loss also makes the elderly often forget their previous experiences. In recent years, affordance has been valued in interaction design. Affordance is proposed by Gibson [2] to represent the interaction between living organisms and the environment. Hartson [3] believes that users should achieve their goals by perceiving, understanding and utilizing affordance when operating products. The affordance of a certain product allows users to know how to operate the product through observation [4]. This research discusses the roles and requirements of various types of affordance in the interaction between elderly users and product interfaces. Future product interfaces for the elderly could be designed on the basis of the research results.

Due to the different perspectives on affordance in interaction design, this research will use the types of affordance proposed by Chen [5] to divide affordance into functional affordance, conventional affordance, and physical affordance.

1.1 Functional Affordance

Functional affordance refers to the design function [3] that can help users complete their work, which is used to indicate the usage of products [5]. Gibson [2] holds that affordance contains all the possibilities of any person taking a certain action in the environment, such as eating an apple either by biting or swallowing. Any product to be used also provides users with all possible usages, while the users’ current intention determines what possible usage they may select. Chen [6] points out that users should perceive the affordance of product during their interaction with the product. During the interaction, users will decide the usage of product according to their behavior intention and product features at that time. If their intention and goals can be satisfied by the usage of product, it proves that the functional affordance of product can be perceived by its users [5].

1.2 Conventional Affordance

Conventional affordance allows users to understand the features of product. For example, a button logo can help users understand what will happen when they click the button [3]. Conventional affordance is indicated in the form of icons, symbols or texts [7]. Blacker [8] believes that designing products based on the previous knowledge of target users can improve the ease of use of products. The previous knowledge and experience of users are highly related to conventional affordance, because they often perceive conventional affordance through culture and convention [5]. In other words, the conventional affordance of product interfaces should be designed taking into account the previous experience and knowledge of users.

1.3 Physical Affordance

Physical affordance can help users to actually operate on product interfaces. For example, a button large enough is convenient for users to press it [3]. Physical affordance is generally expressed by the size, shape, and material of product [9]. Blackler et al. [10, 11] propose that the appearance characteristics of products have the greatest influence on operation time and intuitive use. In interaction design, users perceive the affordance of products on their own, and the appearance characteristics of products are clues to help users operate products correctly [4]. In addition, Chen [5] also believes that physical affordance should correspond to the behaviors, abilities, and body size of users. Therefore, the product interfaces for elderly users should be designed considering the correspondence between the conditions of users and product features.

1.4 Relevance of Affordance to Product Usage

As shown in Fig. 1, users will determine whether the functional affordance supports the intended use according to their own goals. If so, users will start operating their products. During the use of products, users will utilize physical affordance and conventional affordance to achieve their goals by operating these products. For the rice cooker interfaces, we get to know the influence of their affordance on elderly users through focus group interviews.

Fig. 1.
figure 1

Relevance of affordance to user operation (Chen 2007).

Full size image

2 Method

2.1 Design Process

First, we divide affordance into functional affordance (FA), conventional affordance (CA), and physical affordance (PA). Second, we analyze the affordance of each functional component in a rice cooker interface, and carry out focus group interviews (fully recorded by video and audio means) according to the two basic operation procedures of rice cooker interface. Finally, we analyze the interface operation problems, causes, and subjective opinions proposed by the participants of interviews, and summarize the operation behaviors of elderly users and the requirements of all types of affordance in the interface.

2.2 Participants and Product Interfaces

In this research, 10 elderly users aged over 65 are invited to participate in 2 focus group interviews, 5 of which are included in Group A (mean age: 76.0; SD: 6.6) and another 5 of which are included in Group B (mean age: 79.0; SD: 4.7). These two interviews are conducted in two nursing homes in Taiwan. A rice cooker interface, as shown in Fig. 2, is selected as the research tool: “Function Select” button (A), “Cooking” button (B), “Close” button (C), “Timer” button (D), “Hour” button (E), “Minute” button (F), Display Panel (G).

Fig. 2.
figure 2

Rice cooker interface (drawn in this research).

Full size image

3 Results

3.1 Affordance Analysis of Product Interface

The rice cooker interface herein consists of 7 components (see Fig. 2), of which 6 components are operational, including: “Function Select” button (A), “Cooking” button (B), “Close” button (C), “Timer” button (D), “Hour” button (E), and “Minute” button (F). The Display Panel (G) is for viewing only and is not operable. This paper evaluates and analyzes the components of rice cooker interface with three types of affordance, as shown in Table 1. The functional affordance of components is their main functions; the conventional affordance is the operation information expressed by texts, symbols and images on the components; and the physical affordance is the operation mode of components. For example, for the “Function Select” component, its FA is to select cooking mode; its CA is expressed by text; and its PA is expressed by “press with fingers”.

Table 1. Requirements analysis of functional, conventional and physical affordance (prepared by this research).
Full size table

3.2 Affordance Analysis of Operating Task

This paper analyzes two operating tasks of rice cooker, i.e. Cooking and Timer, and their subtasks, along with user operations, as shown in Table 2. For example, for the “Cooking” task, its sub-tasks include “click the ‘Function Select’ button”, “click the ‘Cooking’ button”, and “click the ‘Close’ button”. Involved components include “Function Select” button (A), “Cooking” button (B), and “Close” button (C).

Table 2. List of test operating tasks (prepared by this research).
Full size table

3.3 Analysis of Interview Results

This paper collects the opinions from elderly users in focus group interviews and finds out relevant affordance types for analysis, as shown in Table 3.

Table 3. Affordance analysis for operating tasks (prepared by this research).
Full size table

The results show that most of the problems encountered by participants in Operating Task 1 are arising from CA. For example, participants think that operation steps are complicated and difficult to remember. It is because that this task is inconsistent with the previous experience of participants. Many participants mention that previous products allow them to start cooking by clicking only one button, while the operation steps of new rice cookers are too complicated for them. In Operation Task 2, participants propose that they do not know the function of Timer button, which indicates that the CA of “Timer” button (D) could not be perceived by participants; participants also point out that there are many unnecessary functions on the interface, which indicates that the FA of current rice cooker interface has placed a burden on elderly users and prevented them from direct and quick interaction with products. In both interviews, all participants are able to see the text on the interface and know that they can operate components by pressing relevant buttons. However, participants also think that there are too many components on the interface, indicating that the PA of interface has caused operational obstacles against the participants.

4 Discussion

The interview results show that: In terms of FA, elderly users think that operating tasks are too complicated and many functions are unnecessary. Due to the decline of cognitive abilities, the memory and judgment of elderly users are not as good as average people. The complicated operation steps and excessive functions of current rice cookers increase the cognitive load of elderly users. Norman [4] takes the ease of steps required by users to operate any product as the assessment criteria for product usability. FA is a design function that can help users complete their goals. Excessive functions of current rice cooker interface are unaffordable to the cognition of elderly users. Therefore, the product interfaces for elderly users should be designed to remove unnecessary functions or simplify complicated functions, so that FA can be presented in a simple and clear manner.

In terms of CA, participants find it hard to understand the text on components. In any product interface, CA is indicated in the form of texts, symbols or icons, while the texts, icons, and symbols perceived by users come from their previous knowledge and experience. When the CA of current rice cooker interface is inconsistent with the previous experience of participants, they will not be able to operate the rice cooker effectively. Hartson [3] states that among usability problems, 75% of which relate to CA, and CA is the main mechanism for the learning and memory of all users. His statement is also confirmed in this research. Most of the interface problems of elderly participants of focus group interviews are arising from CA because they fail to learn and remember the CA of interface. Therefore, in the design of product interfaces, the previous experience and knowledge of elderly users can be used to strengthen the CA of components, so that elderly users can use their experience to interact with product interfaces.

In terms of PA, all participants can see the text on interface and know that they can operate components by pressing relevant buttons. However, participants point out that excessive components of interface have prevented them from completing their operation goals. This paper proposes to reduce the number of components, and improve the consistency by the functions, appearance, location and other forms of interfaces as suggested by Blacker [12]. Therefore, the interface components should be designed in a streamlined, regular, and consistent manner, so that PA can be presented in the most effective way.

5 Conclusion

Product design is paying more attention to elderly users due to the aging of population. The understanding and operation abilities of elderly users on product interfaces have gradually declined along with the continuous deterioration of physiological functions, especially cognitive abilities. This research discusses different types of affordance among product interfaces for elderly users, and aims to promote the intuitive interaction between elderly users and product interfaces. The research results show that: (1) Excessive functions on product interfaces place a burden on elderly users. These product interfaces should be designed to reduce the memory load of elderly users by simplifying the FA of interface; (2) the major problem in the interaction between elderly users and product interfaces is that the CA of interface is inconsistent with the cognition of elderly users. The CA of interface should be designed based on the previous experience and knowledge of elderly users; (3) the interface components should be designed in a streamlined, regular, and consistent manner, so that PA can be presented in an effective way to reduce the operating time of elderly users. As a pre-test, this research aims to discuss the affordance requirements of elderly users for product interfaces and provide a basis for the subsequent design of interface affordance. This research only uses rice cooker interfaces as its research tool, and explores the design of product interfaces for elderly users with qualitative methods. In the subsequent researches, different product interfaces and operating tasks will be included and further analysis will be performed by quantitative methods. The affordance of product interfaces for elderly users can be designed based on the conclusions.