Diagnosticity refers to the extent to which a source of data can discriminate between a particular hypothesis and its alternatives. In social situations, individuals often observe others’ behaviors and attempt to form an impression about their personality and aptitudes. As part of this process, individuals test dispositional hypotheses, namely, hypotheses regarding others’ traits and abilities. Diagnostic sources of data are those that discriminate between possessing a particular trait or ability and not possessing the trait or ability.
For example, consider a situation in which a new classmate, John, does not respond to your welcome greetings and you want to know what kind of person he is. You may generate a hypothesis (e.g., “John is unfriendly”), gather information to test this hypothesis, and draw an inference based on the available information. Finding out that John “yelled at a fellow classmate in public” is highly diagnostic information, because such behavior is unlikely to occur unless John is an unfriendly person. Finding out that John dislikes parties has little diagnostic value. This information cannot distinguish between the hypothesis that John is unfriendly and the plausible alternative hypothesis that he is shy, as both unfriendliness and shyness may lead John to dislike parties.
When testing a dispositional hypothesis, one of two broad strategies, distinguished by the extent to which individuals consider alternatives to their chosen hypothesis, may be undertaken. One strategy, called diagnostic hypothesis testing, is employed when individuals search for evidence that bears on both the plausibility of their focal hypothesis as well as on the plausibility of its alternatives. By this strategy, individuals gather information that can distinguish between their chosen hypothesis and alternative ones. Once sufficient information has been gathered, their confidence in their conclusion is high only if the evidence is largely consistent with the chosen hypothesis and inconsistent with its alternatives.
In contrast to diagnostic testing, a second strategy, called pseudodiagnostic hypothesis testing, involves gathering and using information only according to its consistency with the chosen hypothesis. Alternative hypotheses are ignored, or it is simply assumed that information that is consistent with the focal hypothesis is inconsistent with its alternatives. In the previous example, individuals would only ask about John’s unfriendly behaviors and not about his shy behaviors. They would then draw their conclusion on the basis of the extent to which the evidence is consistent with being an unfriendly person, without considering if this evidence is also consistent with other possibilities such as being a shy person. Compared to diagnostic testing, pseudodiagnostic strategy is simple, fast, and relatively effortless. However, when evidence is both consistent with the focal hypothesis and its alternatives, pseudodiagnostic testing might lead to a confirmation bias, namely, a sense of confidence that the evidence supports one’s chosen hypothesis when, in fact, alternative hypotheses may be true.
Research by Yaacov Trope and his colleagues has demonstrated that individuals are sensitive to diagnosticity concerns when testing their hypotheses. That is, they consider alternative hypotheses when searching for information regarding a chosen hypothesis and weighing the evidence against these alternatives when drawing their inferences. For example, when individuals tested a hypothesis that a target person is an extravert, they preferred to ask questions about highly diagnostic introverted behaviors (being quiet) over questions about weakly diagnostic extraverted behaviors (engaging in athletic activities) and when testing a hypothesis that a target person is an introvert they preferred questions about highly diagnostic extraverted behaviors (being friendly) over weakly diagnostic introverted behaviors (listening to classical music). They were also more confident in their inferences when the answers to these questions provided more diagnostic evidence.
However, individuals do not always engage in diagnostic hypothesis testing. Whether individuals will engage in diagnostic or pseudodiagnostic strategies depends on cognitive and motivational resources. When individuals are distracted, their cognitive resources to process information are limited. Similarly, when individuals do not have incentive to reach an accurate conclusion, their motivational resources are low. Under such suboptimal conditions, individuals tend to perform pseudodiagnostic testing. Thus, if individuals are not motivated to reach an accurate conclusion or when they have other things on their mind, they will select and use information that only bears on their chosen hypothesis and ignore information relevant to alternative hypotheses.
Diagnosticity Implications for Dispositional Bias
In many real-life situations, individuals’ behaviors are determined more by situational constraints and less by their personal dispositions. Factors such as group pressures, social norms, and situational stressors can affect the way individuals behave. For example, a person might react aggressively following a situation of strong provocation regardless of whether that person is dispositionally friendly or unfriendly. Diagnostic testing of a dispositional hypothesis considers both the personal disposition (the focal hypothesis) and situational constraints (the alternative hypothesis) as potential causes of a person’s behavior. Consequently, individuals using a diagnostic strategy will not attribute a behavior to the corresponding disposition when strong situational inducements to behave in a certain manner are present. For example, if John’s reaction to your greetings occurred while he was in a hurry to class, then under diagnostic inference this behavior would not be attributed to dispositional unfriendliness since most individuals in this situation would behave in such a way regardless of whether or not they are friendly.
Pseudodiagnostic testing, in contrast, ignores alternative hypotheses and, therefore, may fail to give the proper weight to situational inducements in determining a person’s behavior. Under pseudodiagnostic testing, John’s behavior would still be attributed to dispositional unfriendliness, because the possibility that most individuals, not only those who are unfriendly, would have behaved in such a way when in a hurry is given little consideration. Pseudodiagnostic testing may thus produce a dispositional bias in the inferences individuals draw from others’ behavior. This is particularly likely when individuals’ processing and motivational resources are depleted. Under these circumstances, individuals are likely to rely on pseudodiagnostic testing and conclude that a person’s immediate behavior reflects his or her corresponding personal disposition when alternative situational explanations are no less and even more likely.
Diagnosticity in Self-Evaluation
Diagnostic and nondiagnostic testing strategies are relevant to questions about one’s own dispositions and skills as well. Yet, when a person searches for information bearing on one’s own attributes, other motivations besides reaching an accurate conclusion might play a role. Researchers have proposed three types of motives that guide testing of self-relevant information.
One motive is self-enhancement, namely, the motive to hold favorable self views and therefore seek positive feedback as well as avoid negative feedback regarding self-relevant attributes. A second motive is self-verification, namely, the motive to affirm preexisting self views. These two motives will lead individuals to seek information that may be nondiagnostic of their abilities and personality traits. That is, when self-enhancement goals guide processing of self-relevant information, individuals will only accept information that can bolster their self-esteem, whereas information that might expose their liabilities will be avoided or rejected. Similarly, when self-verification goals guide processing of self-relevant information, individuals will only accept information that can affirm their existing self-views, whether positive or negative, whereas information that proves otherwise will be ignored regardless of its diagnosticity.
A third type of motive that guides self-relevant information processing is self-assessment, namely, the motive to hold accurate self-views that can help one predict the outcomes of future decisions and self-improvement attempts. When self-assessment goals regulate behavior, individuals will prefer diagnostic information regardless of whether it is positive or negative. Self-assessment may also lead to undertaking intermediate difficulty tasks. These tasks are diagnostic of one’s ability because success is more likely given high ability, whereas failure is more likely given low ability. Easy or difficult tasks are nondiagnostic, because success on easy tasks and failure on difficult ones are highly likely regardless of one’s ability level.
As in dispositional hypothesis testing, whether one will engage in diagnostic testing of self-relevant information depends on cognitive and motivational factors. Individuals are more likely to seek diagnostic feedback when they perceive the feedback as pertaining to changeable abilities rather than fixed abilities. This is particularly true for individuals who are uncertain or think that their ability is relatively low. Another factor that has been found to facilitate diagnostic self-assessment is positive mood. Individuals in a positive mood seek positive as well as negative feedback. In contrast, individuals in a neutral or negative mood tend to prefer positive, self-enhancing feedback. It has been proposed that positive mood buffers against the immediate emotional costs of negative feedback and attunes individuals to the long-term, learning benefits of diagnostic feedback.
- Trope, Y., Ferguson, M., & Raghunathan, R. (2001). Mood as a resource in processing self-relevant information. In J. P. Forgas (Ed.), Handbook of affect and social cognition (pp. 256-274). Mahwah, NJ: Erlbaum.
- Trope, Y., Gervey, B., & Bolger, N. (2003). The role of perceived control in overcoming defensive self-evaluations. Journal of Experimental Social Psychology, 39, 407-419.
- Trope, Y., & Liberman, A. (1996). Social hypothesis testing: Cognitive and motivational mechanisms. In E. T. Higgins & A. W. Kruglanski (Eds.), Social psychology: Handbook of basic principles (pp. 239-270). New York: Guilford Press.
- Trope, Y., & Mackie, D. (1987). Sensitivity to alternatives in social hypothesistesting. Journal of Experimental Social Psychology, 23, 445-459.