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CHAPTER 4: Observation 115• Rating scales, often used to measure psychological dimensions, arefrequently treated as if they are interval scales even though they usuallyrepresent ordinal measurement.• Electronic recording devices may be used in natural settings to recordbehavior, and pagers sometimes are used to signal participants to reporttheir behavior (e.g., on a questionnaire).Often researchers are interested only in certain behaviors or specific aspectsof individuals and settings. They may have specific hypotheses about the behaviorthey expect and clear definitions of the behaviors they are investigating.In this type of observational study, researchers typically measure the occurrenceof the specific behavior while making their observations. For example, intheir study of inattentional blindness, Hyman and his colleagues (2009) selectedthe behavior of whether people noticed the clown and quantified the number ofpeople who noticed or did not notice the clown.Suppose you wish to observe people’s reactions to individuals with obviousphysical disabilities using naturalistic observation. First you would needto define who is a “physically disabled person” and what constitutes a “reaction”to such a person. Are you interested in helping behaviors, approach/avoidance behaviors, eye contact, length of conversation, or in another physicalreaction? Next you would need to decide how to measure these behaviors.Assume you choose to measure people’s reactions by observing eye contactbetween individuals with and without physical disabilities. Exactly how shouldyou measure eye contact? Should you simply measure whether an individualdoes or does not make eye contact, or do you want to measure the duration ofany eye contact? Your decisions will depend on the hypotheses or goals of yourstudy, and will be influenced by information gained by reading previous studiesthat used the same or similar behavioral measures. Unfortunately, previousresearch indicates that reactions to physically disabled individuals frequentlycan be classified as unfavorable (Thompson, 1982).Key ConceptMeasurement Scales When researchers decide to measure and quantify specificbehaviors they must decide what scale of measurement to use. There arefour levels of measurement, or measurement scales, that apply to both physicaland psychological measurement: nominal, ordinal, interval, and ratio. The characteristicsof each measurement scale are described in Table 4.2, and a detailedTABLE 4.2CHARACTERISTICS OF MEASUREMENT SCALESType of Scale Operations ObjectiveNominal Equal/not equal Sort stimuli into discrete categoriesOrdinal Greater than/less than Rank-order stimuli on a single dimensionInterval Addition/multiplication/ Specify the distance between stimulisubtraction/divisionon a given dimensionRatio Addition/multiplication Specify the distance between stimulisubtraction/division/on a given dimension and expressformation of ratios of values ratios of scale values