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CHAPTER 4: Observation 117A checklist is often used to record nominal scale measures. To return to ourexample, an observer could record on a checklist whether individuals makeeye contact or do not make eye contact with a physically disabled person, representingtwo discrete categories of behavior (a nominal measure). Checklistsoften include space to record observations regarding characteristics of participants,such as their race, sex, and age, as well as characteristics of the setting,such as time of day, location, and whether other people are present. Researcherstypically are interested in observing behavior as a function of these participantand context variables. For example, Hyman et al. (2009) classified pedestriansin their study of inattentional blindness into four categories based on whetherthey were walking alone or in pairs and whether they were using a cell phoneor music player (note that other categories, such as people walking in groups ofthree or more, were excluded).The second level of measurement, an ordinal scale, involves ordering orranking observations. Tassinary and Hansen (1998) used ordinal measurementto test a specific prediction of evolutionary psychology, namely, that female attractivenessis based on physical cues that simultaneously signal attractivenessand reproductive potential. The specific measure in this theory is the waist-tohipratio, with hips wider than waist indicating greater reproductive potential.In their study, undergraduates rank-ordered line drawings of female figuresthat varied in terms of height, weight, and hip size. That is, they ordered thedrawings from least attractive to most attractive. Contrary to the predictionbased on evolutionary psychology, physical attractiveness of the figures wasdirectly and negatively related only to hip size, not the waist-to-hip ratio.Drawings with wider hips were more likely to be rank-ordered as lower inattractiveness.In order to quantify behavior in an observational study, observers sometimesmake ratings of behaviors and events based on their subjective judgments aboutthe degree or quantity of some trait or condition (see Brandt, 1972). For example,Dickie (1987) asked trained observers to rate parent-infant interactionsin a study designed to assess the effect of a parent training program. Observersvisited the home and asked parents to “act as normal as possible—just as if we[the observers] weren’t here.” Observers made ratings using 7-point scales on13 dimensions describing characteristics of verbal, physical, and emotional interaction.Ratings of 1 represented the absence or very little of the characteristic,and larger numbers represented increasing amounts of the trait. An exampleof one dimension, “parent’s warmth and affection toward infant” is describedin Table 4.3. Note that precise verbal descriptions are given for the four oddnumberedscale values to help the observers define different degrees of thistrait. The even-numbered values (2, 4, 6) are used by observers to rate behaviorsthat they judge fall between the defined values. Based on observers’ ratings,parents who took part in the program aimed at helping them to deal with theirinfant were rated higher on many of the 13 parent-child interaction variablesthan were parents who did not participate in the program.At first glance, a rating scale such as the one in Table 4.3 appears to representan interval scale of measurement—there is no true zero and the intervals betweennumbers appear to be equal. Closer examination, however, reveals that