People often use heuristics (simple rules-of-thumb or shortcuts in thinking) to help simplify difficult judgements that they need to make in their everyday lives.
It is reasonable to assume that they do this when judging energy consumption and energy saving too. Mains-supplied electricity and gas are largely invisible to end-users (Burgess & Nye, 2008; Kidd & Williams, 2008) and cannot be di-rectly seen, touched, or heard. Unlike judging the amount of wood burnt from a woodpile in a week, which would be highly visible, householders must judge the amount of gas and electricity that they have used for multiple purposes through-out the week. Householders can typically only infer indirectly how much is con-sumed by their individual appliances. It is plausible that they might base their inferences on physical or other features of the appliance itself that they perceive
to be correlated with energy consumption (as described by Read & Grushka-Cockayne, 2011). The relationship between these features (e.g. the size of the appliance) and the energy consumption of an appliance are learnt from past ex-perience or from other people, or just applied from perceptions of the world in general (e.g. that larger things tend to contain more stuff or require more effort to move). Inferring energy consumption (and energy savings) indirectly like this enables people to make judgements that they would otherwise be unable to at-tempt, or not without considerable effort to acquire more knowledge.
Traditionally, it has been assumed that people use, or try to use, “rational” ap-proaches to making judgements (Oppenheimer & Kelso, 2015; Payne et al., 1993;
Shah & Oppenheimer, 2008; Vlaev, Chater, Stewart, & Brown, 2011). Accord-ing to this approach, when people make judgements about how much energy an appliance consumes, they recall from memory (or research externally) all the information that is relevant to the judgement. They then weigh up the relative im-portance of each piece of information and consider all the weighted information in making the judgement (Payne et al., 1993; Shah & Oppenheimer, 2008). For ex-ample, a kettle might have multiple features (or attributes): it draws 3000 Watts of power when switched on, it is small, it is used five times a day, it is switched on for only three minutes at a time. The person might consider the size of the ap-pliance to be relatively unimportant to its energy consumption and weight that lower than the other features. They might then try to balance the power draw against the number of hours that the appliance has used over the last 30 days in order to come to an estimation of the number of kilowatt hours consumed by the appliance. Doing the same calculation for the washing machine would then reveal which of the two appliances consumes the most energy. Of course, many more factors could be relevant than included in this relatively simplistic exam-ple, such as the amount of water heated by each appliance, which settings are selected for the washing machine cycles, and so on. Such an approach to making judgements is time-consuming and can require large cognitive effort, so it is just not feasible for every single judgement that a person makes in their daily life.
People use heuristics to reduce the amount of effort a judgement would take if they were to use a more complex approach (Gigerenzer & Gaissmaier, 2011;
Shah & Oppenheimer, 2008). Heuristics are shortcuts that involve using rules-of-thumb about what information is relevant and relied upon in making a judge-ment. The heuristic process of feature substitution (also known as attribute substi-tution) works in this way (Kahneman & Frederick, 2002; Shah & Oppenheimer, 2008): “when confronted with a difficult question people often answer an eas-ier one instead, usually without being aware of the substitution” (Kahneman and Frederick, 2002, p. 53). When searching their memory for information from which they can recall or deduce the energy consumption of the appliance (information that they might not even have), they more easily retrieve related information about features of the appliance (e.g. its size) and use that information instead.
According to Kahneman and Frederick (2002), this kind of substitution is used when it is difficult or impossible to know the value of the target feature (e.g.
energy consumption), an associated piece of information from a heuristic cue is easier to access (from memory or from the external environment, such as the ap-pliance itself), and the person does not override the use of the easier cue in favour of spending more time and cognitive resources searching for and weighing up other information.
Heuristic processing is used to save effort unless the person deems it nec-essary to be more careful in weighing up all the information before making a judgement. Kahneman and Frederick (2002) argued that heuristic processing oc-curs quickly, intuitively, and automatically but that it could be overridden by more slow, systematic, and deliberate thinking if necessary (see also Evans, 2014;
Evans & Stanovich, 2013; Kahneman, 2011). Some researchers argue that people do not have two types of thinking and that people use heuristics because they are just the most efficient way to make a judgement that is as good as, or some-times better than, using a more complex approach (Gigerenzer & Gaissmaier, 2011). Gigerenzer and Gaissmaier (2011) agree with other researchers, however, that heuristics can be used consciously or unconsciously and that people’s use of heuristics varies according to various factors: the judgement itself (e.g. how it is presented and the context it is in), the abilities and available time of the person making the judgement (e.g. cognitive ability, prior knowledge and experience, and time pressures), and the social context of the judgement (e.g. the perceived importance of accuracy for the judgement) (Gigerenzer & Gaissmaier, 2011; Lee
& Cummins, 2004; Newell, 2005; Pachur & Bröder, 2013; Payne et al., 1993).
Only a limited amount of research has investigated how people make energy
judgements instead of just assessing the accuracy of their judgements. The re-search in this thesis explores what cues (features of energy-consuming appliances or energy-saving measures) people might use in feature substitution processes to infer energy consumption and savings. The next section reviews the small num-ber of studies in the literature over the past 35 years that have investigated the cues that people might use to infer the energy consumption of appliances. No previous research has investigated the use of heuristic cues in energy savings judgements so the following systematic literature review focuses only on studies that have investigated the use of cues in energy consumption judgements. Part II of this thesis explores the use of cues in energy savings judgements.