Affect is the term psychologists use to describe a person’s feelings. Measures of affect can be thought of as measures of particular feelings or emotional states, and they are typically measured with reference to a particular point in time. Such measures capture how people experience life rather than how they remember it (Kahneman and Krueger, 2006). While an overall evaluation of life can be captured in a single measure, affect has at least two distinct hedonic dimensions: positive affect and negative affect (Kahneman et al., 1999; Diener et al., 1999). Positive affect captures positive emotions such as the experience of happiness, joy and contentment. Negative affect, on the other hand, comprises the experience of unpleasant emotional states such as sadness, anger, fear and anxiety. While positive affect is thought to be largely uni-dimensional (in that positive emotions are strongly correlated with each other and therefore can be represented on a single axis of measurement), negative affect may be more multi-dimensional. For example, it is possible to imagine at one given moment feeling anger but not fear or sadness.
The multi-dimensional nature of affect raises an interesting question about the relationship of affective states to life evaluation. Life evaluations are uni-dimensional in that different experiences can be rated unambiguously as better or worse. Kahneman et al. (1999), argues for the existence of a “good/bad” axis on which people are able to place experiences based on the emotional states they are experiencing. In effect, he argues, people are able to make an overall judgement about the net impact of their affective state at a particular point in time. In principle, this is the same process that is involved in forming life evaluations from remembered affective states. Kahneman’s point is that affective states can be compared, and that one can therefore reasonably aggregate measures of current affect. For this reason, affect measures are sometimes reported in terms of affect balance, which captures the net balance between positive and negative affect (Kahneman and Krueger, 2006).
The measurement of affect poses different challenges to the measurement of life evaluation. It is difficult to ask people to recall affective states in the past, since responses will be affected by recall biases such as the peak/end rule mentioned above. The gold standard for measuring affect is the experience sampling method (ESM), where participants are prompted to record their feelings and perhaps the activity they are undertaking at either random or fixed time points, usually several times a day, throughout the study period, which can last several weeks. To maximise response rates and ensure compliance throughout the day, electronic diaries are often used to record the time of response. While the ESM produces an accurate record of affect, it is also expensive to implement and intrusive for respondents.
A more viable approach is the use of the day reconstruction method (DRM), in which respondents are questioned about events from a time-use diary recorded on the previous day. Research has shown that the DRM produces results comparable with ESM, but with a much lower respondent burden (Kahneman et al., 2004). Experience Sampling, the DRM and similar methods for collecting affect data in time-use studies allow for analysis that associates particular affective states with specific activities. It is also possible to collect affect data in general household surveys.4 However, affect measures collected in general household surveys lose some detail due to the need to recall affect (even if only what affective states the respondent experienced on the previous day) and also cannot easily capture information linking affect to particular activities.