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36 PART I: General Issuesand measure it. Intelligence, for instance, can be defined operationally by usinga paper-and-pencil test emphasizing understanding of logical relationships,short-term memory, and familiarity with the meaning of words. Some may notlike this operational definition of intelligence, but once a particular test has beenidentified, there can at least be no argument about what intelligence meansaccording to this definition. Operational definitions facilitate communication, atleast among those who know how and why they are used.Although exact meaning is conveyed via operational definitions, this approachto communicating about constructs has not escaped criticism. One problem hasbeen alluded to already. That is, if we don’t like one operational definition ofintelligence, there is nothing to prevent us from giving intelligence anotheroperational definition. Does this mean that there are as many kinds of intelligenceas there are operational definitions? The answer, unfortunately, is that wedon’t really know. To determine whether a different procedure or test yields anew definition of intelligence, we would have to seek additional evidence. Forexample, do people who score high on one test also score high on the second test?If they do, the new test may be measuring the same construct as the old one.Another criticism of using operational definitions is that the definitions arenot always meaningful. This is particularly relevant in cross-cultural researchwhere, for example, a paper-and-pencil test of intelligence may tap into knowledgethat is specific to a particular cultural context. How do we decide whethera construct has been meaningfully defined? Once again, the solution is toappeal to other forms of evidence. How does performance on one test compareto performance on other tasks that are commonly accepted as measures of intelligence?Scientists are generally aware of the limitations of operational definitions;however, a major strength of using operational definitions is that theyhelp to clarify communication among scientists about their constructs. Thisstrength is assumed to outweigh the limitations.InstrumentsYou depend on instruments to measure events more than you probably realize.For example, you rely on the speedometer in a car and the clock in your bedroom,and you can appreciate the problems that arise when these instrumentsare inaccurate. Accuracy refers to the difference between what an instrumentsays is true and what is known to be true. A clock that is consistently 5 minutesslow is not very accurate. Inaccurate clocks can make us late, and inaccuratespeedometers can earn us traffic tickets. The accuracy of an instrument is determinedby calibrating it, or checking it with another instrument known to be true.Measurements can be made at varying levels of precision. A measure of timein tenths of a second is not as precise as one that is in hundredths of a second.One instrument that yields imprecise measures is the gas gauge in most oldercars. Although reasonably accurate, gas gauges do not give precise readings.Most of us have wished at one time or another that the gas gauge would permitus to determine whether we had that extra half gallon of gas that would get usto the next service station.We also need instruments to measure behavior. You can be assured thatthe precision, and even the accuracy, of instruments used in psychology have