Other self-guided exercises investigated by Seligman and colleagues (2005) asked people to focus on their own personal strengths. In one case, participants were asked both to identify their particular strengths and to use them more often during the next week. In another experimental condition, the instruction was to use one of your principal strengths in a new and different way to every day for a week. Both interventions led to increased happiness relative to a placebo control group, with the impact of the second one extending further into the study’s 6-month follow-up period.
Experimental studies of this kind are important for both theoretical and practical reasons. In theoretical terms, experimental comparisons between exercise conditions can increase understanding of causality, advancing beyond the correlational research into judgment processes summarized earlier in the chapter. It also permits examination of possible contingency factors. The hedonic value of an intervention depends not only on its content, but also on its intensity, duration, and frequency, as well as on the characteristics of the individuals involved and on the indicators of happiness that are examined. For example, thinking in a grateful manner is a less substantial activity than making a visit to express gratitude in a face-to-face encounter; further, in terms of particular outcomes, gratitude might have more impact on well-being that involves low arousal (the bottom-right section of Figs.2.1 and 2.2), whereas reflecting on your personal strengths may more bear on the top-right section---activated pleasure. Additional experimental research into main and interactive effects is clearly much needed.