Pictures and text in instructions for medical devices: Effects on recall and actual performance

https://doi.org/10.1016/j.pec.2005.12.003Get rights and content

Abstract

Objective

The present study aimed to contribute to the design of effective health education information. Based on cognitive-psychological theory, pictures were expected to improve understanding of two existing textual instructions for using asthma devices (inhaler chamber and peak flow meter). From an analysis of the affordances and constraints of both devices this effect was expected to be stronger with the inhaler chamber than with the peak flow meter.

Methods

To test this, both instructions were systematically illustrated with seven line-drawings visualizing the actions. In two separate randomized controlled trials with in total 99 participants from the general public, the original text-only versions were compared to the text-picture versions of the same instruction. Dependent variables were participants’ recall of the instructions and the quality of their performance with the instruction observed from video-recordings.

Results

Conform expectations, the results showed significant positive effects of pictures on recall and performance in both instructions, especially with the inhaler chamber.

Conclusion

Thus, pictures may contribute to a better comprehension and use of medical devices that are inherently less clear.

Practice implications

Health educators may optimize instruction design by careful analysis of the device with instruction and observational testing with potential users.

Introduction

In the development of health education materials, very little research is done into how graphical design affects comprehension of information. At most, with a basic notion that pictorial information can aid readability of a brochure text, studies have simultaneously changed text and added pictures to concretize or make the information more interesting to readers [1], [2]. However, from instructional design research we know that the presence of pictorial information allows readers to visualize relations in the text [3], enabling the formation of a mental model of the situation, which may enhance understanding of text [4], [5], [6].

The present study aimed at testing the additive value of illustrations in medical instructions that were originally part of a health education brochure. Based on research in instructional design [7], [8], it was predicted that when more thought is put into including pictures in such information, this could aid text comprehension. Especially with unfamiliar devices or ambiguous instructions, such effects may be strong. To test these assumptions, we added simple line-drawings in two text-only instructions from an existing asthma brochure [9] for using two devices, the ‘inhaler chamber’ and ‘peak flow meter’. Based on a usability-analysis, illustrations were expected to have a stronger effect with the inhaler chamber than with the peak flow meter. Objective measures were used to assess comprehension.

In the field of instructional design, pictures have been found to improve learning [7], [10], which is explained in terms of a ‘mental model theory’ [4], [6], [5]. Mental model theory states that through different processing routes, text and pictures enable construction of both verbally (‘propositional’)- and visually-based mental models. These are integrated by the reader in their working memory to foster comprehension [5]. When presented alone, text has been found to need more cognitive resources than pictures, because it has to be mentally transformed into a propositional representation and then into a mental model of the situation. Pictures, on the other hand, are considered to be external models (i.e. analogical visual representations) that directly allow the construction of a mental model of the situation [11].

Readers are best able to build connections between these two representations when the corresponding text and picture are in working memory at the same time [12]. As working memory is limited in time and processing capacity, this concurrent activation is most likely to happen with contiguous presentation of text and illustrations [5], [8], illustrating a ‘spatial-contiguity effect’ [13]. One possibility is adding textual captions [14] to illustrations explaining the important aspects of the picture's content.

Pictures may contain ‘depicting codes’ and ‘directing codes’. ‘Depicting codes’ simulate characteristics as they are perceived in the real world [15], for instance, photographs depicting the text-subject. Such pictures may serve a representational or a decorative function: text content is merely repeated or the text is made more esthetical to increase the readers’ interest, respectively [16]. ‘Directing codes’, on the other hand, deviate from real world appearance and typically aim to convey a visual argument. Arrows and exaggerations of specific elements, for example, can prompt the reader's attention to relevant picture details (‘visual cueing’ [17]) and can direct such cognitive processes as comparing, generating inferences, and imagining motion [15]. When inferring movement in procedural pictorial instructions, people have been found not to make inferences unless such movement is expressed explicitly with text or arrows in pictures [18].

With procedural instructions such as in the present study, when users have formed an understanding (mental model) of the information, this information should be acted upon. In doing this, several cognitive activities are performed by readers in their working memory, ranging from setting a goal and integrating information from the instructional document, the to-be-used device, and prior knowledge, to action planning, execution, and monitoring the actions [19]. To avoid cognitive overload, readers can reduce the amount of information to process by switching regularly between the instruction and the actions to perform. The design of procedural instructions which supports such step-by-step strategies has indeed been found to shorten execution time and reduce errors in performance [20], [21].

With procedural instructions also, a combination of text and pictures generally leads to superior performance compared to text alone [22]. With text-only procedural instructions, readers perform ‘macro-switches’ between the text and the device to match textual and visual information before planning the actions described. However, when pictures accompany the text, the reader can perform ‘micro-switches’ between the text and relevant visual elements inside the document. This could take up less working memory resources, because more precise information is given about what to do (in the text) and where to do it (in the picture) [19] before switching to the device to perform the actions.

Research of pictures in procedural instructions mainly focuses on relatively technical devices [22] and complicated compilations of parts [11], [21], [23], of which the actions to perform are not obvious to novice users. However, with devices that have a higher inherent clarity the contributing value of pictures may be lower. In cognitive ergonomics, a research area aimed at studying and improving the usability of devices, such inherent clarity is described in terms of ‘affordances’ and ‘constraints’ [24]. Affordances refer to characteristics of objects that are perceived by their users regarding their potential use: objects permit and even provoke certain user-actions because of their form, weight or materials. For instance, a smooth round red button lifted a centimeter from a surface, affords pushing it. Constraints, on the other hand, refer to an object's characteristics that limit possible actions. Scissors, for instance, have two holes with different sizes, limiting the number of fingers you can put through each of them, and the scissors only move in one direction. These constraints help the user identify the proper use. Thus, a device may be inherently clear, or require minimal explanations. Pictures may add very little in such circumstances.

The aim of the present study was to test the predictions that illustrations would promote understanding of the information more than text-only instructions and that this effect may be stronger with an inherently ambiguous rather than clear device. With the starting point of improving an asthma brochure distributed by the national Dutch asthma fund, instructions were taken for the use of two medical asthma devices: the inhaler chamber and the peak flow meter. The first is a device for using a pressurized metered dose inhaler (pMDI) when people have difficulties inhaling from the pMDI itself and the second is a device to measure the degree of airway constriction (see also Fig. 1, Fig. 2). A human factors specialist (the first author) had a critical look at all features of both devices in light of their affordances and constraints, and evaluated them accordingly. The peak flow meter is a tube with one round pointy opening at the front, which was expected to afford blowing in it. The presence of a scale with a pointer that only moves when blowing in the tube contributes to this affordance. Being a non-transparent object with a closed end constraining the possibility for blowing on the wrong end, it would be a challenge to use it differently. The only information that may not be communicated by the device itself pertains to bodily positions when using it; relatively simple ‘actions’ that people perform daily to some extent and thus may not be entirely unfamiliar.

The inhaler chamber has a small round extended opening on one side of the tube which affords putting it in one's mouth. A curved holder on the other side of the tube is the only place where the pMDI fits, constraining the placement of the pump on the chamber. However, the inhaler chamber has multiple features (valves) that should not be used but afford pushing them. In other words, without any explanation novice users could perform a number of undesirable actions with the inhaler chamber and pump, whereas with the peak flow meter the possibilities are obviously limited. Thus, the inhaler chamber was expected to benefit more from pictures than the peak flow meter. To test this, the present study comprised two separate but identical tests, each comparing a text-only with an illustrated version of the instruction. Understanding of the information was tested with open recall and several performance measures when following the instructions, in line with the general need for performance-based evaluation of (health education) instructions [25].

Section snippets

Participants

Ninety-nine participants were randomly assigned to one of four groups in two separate between-participants designs. Participants were members of the general population between 20 and 60 years of age, who had responded on posters and flyers in their local supermarkets. To counter undesirable effects of prior knowledge, participants were selected based on the criterion that they had no experience with devices for asthma-patients. There were 26 participants in the inhaler chamber text-only (11

Results

In Table 1, mean scores and standard deviations of each group on all continuous measures are presented. Test-results are presented below per variable for both devices.

Discussion

Altogether, the presence of pictures in instructions for medical devices did seem to have an added value over text alone. Also, as expected, this was especially the case for the inhaler chamber and to a lesser extent for the peak flow meter instruction. With the peak flow meter, both text-only and text-picture versions of the instruction brought about comparable recall of the instruction and performance with the device. Here, the presence of the pictures only seemed to contribute slightly to a

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