Diferencias entre gram positivas y gram negativas

exhibit such a bias then it is hardly surprising that research by social psychologists reports the same phemomena in the intuitive scientist.

Research into self-fulfilling prophecies (Jones,1977) demonstrates that expectations about ourselves and others influences both our own behaviour and that of others in such a way as to confirm these expectations (Shaklee & Fischhoff, 1979). Self-fulfilling prophecies operate in two

22

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ways: (1) where people see what they expect to. Chapman & Chapman (1969) show people perceive expected relationships in information when it is not there; (2) where an agent causes an actor to behave uncharacteristically but in a way expected by the agent (Snyder and Swann, 1978a,b; Snyder, in Press). Snyder & Swann (1978a), for example, show that a perceiver's falsely held beliefs about another person cause him to behave in a manner likely to confirm those beliefs. In testing out one’s beliefs, Snyder & Swann (1978a) argue "reality testing has become reality constructing" (pl59). According to Snyder (in Press) :

"Confirmatory hypothesis-testing strategies may constrain targets to behave in ways that provide actual behavioural evidence that will appear to confirm the hypothesis under scrutiny"

(p25).

Labelling theory (Scheff, 1974) and the effects of stigmatisation (Goffman, 1963) provide good examples of this.

Cognitive dissonance theory predicts that defective information search or biased exposure to consistency-maintaining types of

information in order to bolster the chosen alternatives is the major way of reducing post-decisional dissonance (Festinger, 1964). What also appears to occur is that biased information processing takes

i

place before a decision is made. This happens because people

experience pre-decisional dissonance as well. Empirical support for this comes from a number of studies, for example, Janis & Mann (1977); Fellner & Marshall (1970); Simmons et al (1973). Janis & Mann (1977) show,on the basis of numerous interviews with decision-makers, that people employ numerous "bolstering" tactics when appraising possible choice alternatives. One such tactic they discuss is that of

23.

"exaggerating favourable consequences" another is "minimising unfavourable alternatives" (p91). In the case of the former decision-makers are found to pay most attention to the favourable consequences of a choice alternative in order to justify the costs and risks involved. Such attention in itself may well make the favourable consequences seem more likely, as Carroll (1978) has shown. In the case of the latter tactic the decision-maker is found to characterise the undesirable outcomes to a preferred alternative as less bad than they really are, again allowing him to rationalise the costs and risks involved. To summarise, where people have preferences for certain alternatives it is often found that pre- decisional dissonance will arise as other alternatives may be objectively equally attractive. In order to reduce this dissonance "bolstering" strategies may be employed, this means that information search or assimilation may often be biased.

However, information assimilation to pre-existing opinions, beliefs or theories is not something that necessarily leads to bias. As Jervis

(1976) points out "intelligent decision-making in any sphere is impossible unless significant amounts of information are assimilated to pre-existing beliefs" (pl45). However, circumstances arise in which people maintain

i their theories or beliefs in the face of clearly discontinuing or contra­ dictory evidence (Schum, 1977; Engquist et a l , 1976 ; Tucker & Rowe,1979; Erlhom & Hogarth, 1978; Wyer, 1977; Ross et a l , 1975; Lord et a l , 1979; Massad, Hubbard & Newson, 1979).

This position is summarised by Kinder & Weiss (1978), who say that "The pursuit of consistency becomes irrational as persistence and denial come to dominate openness and flexibility" (p7lO). Inappropriate

24.

Ross, Lepper & Hubbard (1979) using a "total discrediting" or "debriefing" paradigm. Subjects were given the task of sorting

suicide notes, distinguishing those which were authentic from those which were not. They were given one of three types of false feedback:

(a) success — indicating that they had made much more accurate judgments than the average student; (b) failure — indicating that they had made much worse judgments than the average student; or (c) average — indicating that they had been as successful in correct categorisation as the average student. Following this subjects were "debriefed" and told that the feedback they had received had been completely false. Ross, Lepper & Hubbard explained at length to the subjects that the feedback

they had received had been pre-arranged and determined randomly. They

even showed subjects the actual schedule which determined which of the above three conditions the subject had been assigned to and the pre­ determined feedback given. In short, subjects were told that the way they had classified the notes bore no relation to how the experimenter had informed them that they had classified the notes.

The results for both participants and observers revealed an

extensive degree of post-debriefing perseverence. When asked how many

answers (a) they thought they had got correct; (b) they would get correct on a second trial; (c) the average student would get correct; it was found that subjects in the success condition estimated a significantly greater number correct than subjects in the failure condition. Subjects in the average condition fell in between. Furthermore, subjects rated their own ability at such a task as greater when they experienced "success" rather than "failure". Observers, who watched actors perform the task

25

also showed perseverence in a similar way. In a further attempt to reduce perseverence, the second experiment included a "process­ debriefing condition”. Here subjects received the same debriefing information as outlined above together with a description and

explanation of perseverence itself. It was found that participants

demonstrated little perseverence, but actors still showed the effect.

Further demonstration of perseverence is given by Ross & Anderson (1979). They and Ross, Lepper & Hubbard (1979) argue that perseverence reflects the operation of two processes in social-judgment. Firstly, that initial impressions, once formed, are difficult to change — this relates to the primary effect in impression formation (see Chapter 4 for more detailed discussion). Secondly, and more importantly, they propose that "first impressions may not only be enhanced by subsequent biases in coding but may ultimately be sustained through such biases" (p889). In general then, once an initial scheme for assimilating and coding data is arrived at people are extremely reluctant to abandon it and formulate another.

The idea of a scheme is similar to Jervis' (1976) notion of an "image". He argues that one of the most important tasks for decision­ makers formulating foreign policy is to discover the intentions of the other nation. Jervis shows that 'images' of others' intentions determine how information is processed and that images are often retained, irration­ ally, in the face of overwhelming conflicting evidence.

Maintenance of beliefs or "theories" by biased assimilation of new information is demonstrated in a study by Lord, Ross & Lepper (1979). They used the issue of capital punishment for murder and selected subjects who either strongly opposed or strongly favoured it. Both groups were shown two "real" studies, one supporting and one opposing its deterrent

effect, in a counterbalanced design. There were three main findings: (1) the study which supported subjects' position was rated as more convincing and better conducted than the conflicting study; (2) if the first study subjects read supported their position it served to strengthen it; however, no change in opinions was found if the first study read opposed their position; (3) subjects were found to be more convinced of their view after reading both studies than before reading any of them.

The first two findings do not necessarily imply that irrational procedure for processing information is being employed. As Lord, Ross and Lepper (1979) point out: "our subjects' main inferential shortcoming ...did not lie in their willingness to process evidence in a biased manner. Willingness to interpret new evidence in the light of past knowledge and experience is essential for any organism to make sense of and respond adaptively to, its environment" (p2107).

However, the third finding does constitute serious bias and a departure from rationality. To quote Lord, Ross & Lepper (1979), subjects' "sin lay in the readiness to use evidence processed in a biased manner to bolster the very theory or belief that "initially justified" the processing bias"(p2lo7). It is tempting to say that the subjects used a form of "grooved thinking", (Steinbruner 1974), and what Jervis (1976) calls "excessive and premature cognitive closure" (pl87).

Jervis argues in agreement with other research (for example, Bruner 1957; Haber, 1966), that assimilation of information to pre-existing beliefs or theories is obviously necessary if decision-makers are to function at all in such a complex environment. However, it becomes irrational (i.e. excessive and premature cognitive closure occurs) when

such beliefs have become inappropriate. This occurs when relevant . information is ignored or discredited or when the rules for

assimilating information exhibit bias. The two experiments outlined

above demonstrate just such bias in assimilating and processing information.

In summary, Ross, Lepper & Hubbard (1975) and Lord, Ross & Lepper (1979) demonstrate that not only do beliefs, impressions, etc., persevere in the face of information which discredits the validity for holding them, but also that presentation of mixed evidence causes beliefs, impressions, etc., to be strengthened. Mahoney (1977) shows similar processes operating with professional scientists. He reports that journal article reveiwers are more critical of experiments which conflict with their own theoretical perspective than they are of experiments which confirm their own views.

In conclusion, the research reviewed in this section greatly extends and supplements the way in which the striving for cognitive consistency affects our judgments and decision-making processes. Perseverence and biased assimilation of information demonstrates that initially formed opinions and strongly held beliefs are maintained, often quite inappro­ priately, by the power of congitive consistency. In many cases our cognitive apparatus makes it easier for us to reduce complexity and conflicting information by assimilating it to pre-existing beliefs, which

♦ J we may have little or no grounds for holding. Such a strategy is often adaptive and correct, but at other times is the source of serious error and bias.

2.2.3. Heuristics of Thinking.

The ways in which we make judgments under uncertainty in a complex social environment does not appear to accord with rational models of man

(Simon, 1957; Slovic, 1972; Abelson, 1974; Steinbruner, 1974; Nisbett and Ross, 1980). Rather than use formal rules of inference which, if

correctly implemented, would guarantee success man is characterised as operating with a number of informal rules or heuristics of thinking (Kahneman & Tversky, 1972, 1973, 1979; Tversky & Kahneman, 1971, 1973, 1974; Ajzen, 1977). These heuristics which are used to reduce potentially complex inferential tasks to more manageable, simpler judgmental operations, often lead to serious shortcomings and bias. Of course, they are often used with success. However, because they have no analogue in a formal model overuse and inappropriate use lead to undesirable consequences. This section describes some of these heuristics and indicates how they may lead to bias and error. Links with other biases and errors discusssed in other sections of this chapter are also indicated. The heuristics of thinking to be discussed provide explanations of the other shortcomings in social inference. It is beyond the scope of this chapter to provide any great detail to the latter consideration — the interested reader is referred to Nisbett and Ross (1980); Tversky, Kahneman a Slovic, (1980) where greater discussion is given to this.

In making judgments, inferences and decisions, Tversky & Kahneman propose that people make use of simple intuitive heuristics rather than using sophisticated, formal rules. Three heuristics — availability,

< representativeness and anchoring and adjustment -- are examples of this. These are not explicit rules of thumb that people use but are "automatic and non-reflective and notably free of any conscious consideration of appropriateness (Nisbett a Ross, 1980, pl8) .

(a) The Availability Heuristic.

The availability heuristic is used by people when engaged in the task of estimating the frequency of some category or objects or the

probability of some event occurring. Simply stated, the frequency of a class or probability' of an event is judged by the ease with which relevant instances or occurrences can be brought to mind

(Tversky & Kahneman, 1974). Availability is regarded as an "ecolo­ gically valid cue for the judgment of frequency because, in general, frequent events are easier to recall or imagine than infrequent ones" (Tversky & Kahneman, 1973 p209). That is, experience

"has taught us that instances of large classes are recalled better and faster than instances of less frequent classes, that likely occurrences are easier to imagine than unlikely ones, and that associative connections are strengthened when two events frequently co-occur. Thus a person could estimate the numerosity of a class, the likelihood of an event, or the frequency of co-occurrances by assessing the ease with which the relevant mental operation of retrieval, construction or association can be carried out"

(Tversky & Kahneman, p208).

Bias and error occur with the use of the availability heuristic because factors other than frequency or probability (for example, the efficiency of memory search) affect the ease with which instances can be retrieved from memory.

Tversky & Kahneman (1973) report a number of studies which demonstrate how use of the availability heuristic may lead to bias.

In one study subjects were presented with the names of famous personalities of both sexes. Some of the names were better known than others. The task was to estimate whether the list contained more males or females and to recall the names on the list. It was found that subjects con­ sistently overestimated the frequency of the sex that had more famous names and recalled more very well known names than less well known ones.

*

In another experiment subjects were asked to judge the relative frequency of two types of English words — those beginning with the letter R or those where the third letter is R. Of 152 subjects 105 judged words beginning with R to be more frequent. in fact words with R as the third letter are much more numerous. Bias due to availability occurs here because people find it easier to generate words beginning with the letter R than with R as the third letter. The most available words are those which are generated easiest and hence frequency estimation is biased.

For similar reasons Coombs & Slovic (1978) show that newspaper reporting of more dramatic and exciting causes of death leads people to perceive those causes of death as more frequent than less dramatic, rarely reported ones. In fact, the latter causes are often more frequent than the former. Lichtenstein et al (1978) provide additional support for this.

Rothbart et al (1978) show that people with more extreme personality characteristics were judged (wrongly) to appear more frequently than those with "mild characteristics" in an impression formation task. They argue that extreme characteristics are more available from memory because of their vividness. This is a similar explanation to that of Coombs and

l Slovic (1978); Lichtenstein et al (1978).

Estimating the probability of occurrance of some social event or outcome can also be influenced by the availability heuristic. This may be due to the ease with which relevant stories, senarios or "scripts"

(Schank & Abelson, 1977) can be brought to mind. How plausible such scenarios are, the number of relevant scripts that can be imagined, or the difficulty in producing scenarios may all affect likelihood assess­ ments through availability.

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This is demonstrated by Ross et al (1977). They found that

subjects who were provided with a causal explanation as to why some event should occur from a specified set of antecedent events gave higher likelihood assessments to that outcome than those not provided with a causal explanation. Carroll (1978) has gone even further and

shown that just asking subjects to imagine an event turning out in a certain way increases its perceived likelihood. Taylor & Fiske

(1975, 1978) generalised this and showed that any strategy which focuses people's attention on potential causes affects their judgment.

Future expectations can also be biased by the availability of instances from past experience. Slovic, Kunreuther & White (1974) show that protection against natural hazard, such as flooding, is often inadequate because people are unable to imagine how future floods could be any different from ones they have experienced. Thus precautions are taken which would be successful with past floods but not necessarily able to cope with future ones. Slovic & Fischhoff

(1979) make a similar point with respect to hazard management in nuclear energy.

In summary, availability appears to be a widely used inferential tool. Its misuse and inappropriate application leads to bias. In

i general, the availability heuristic is most likely to be used when individual instances, scenarios, etc., are used to judge the frequency or probability of events. When generic features come to the fore the

representative heuristic is most likely to be employed. It is to

3 2

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(b) The Repreaentativaness Heuristic.

The representativeness heuristic (Kahneman & Tversky, 1972,1973; Tversky & Kahneman, 1974) is used to judge the probability of an event or a sample "by the degree to which it is: (i) similar in essential properties to its parent population; and (ii) reflects the salient features of the process by which it is generated" (Tversky & Kahneman, 1972,p431) . This heuristic permits people to simplify inferential judgments to ones of simple similarity. An event or instance will be assigned to one category rather than another depending upon the degree to which its salient features represent that category rather than another. In relying on this heuristic, people tend to pay greater attention to more salient, vivid and redundant features of an event rather than base their judgments on more diagnostic information such as base rates and the reliability and validity of the data.

Kahneman & Tversky (1972) report a number of studies demonstrating how the inappropriate use of representativeness leads to biased sub­ jective probability estimates. In one study, for example, subjects were shown the following sequences of coin tosses:

(i) H T T H T H (ii) H H H H T H and (iii) H H H T T T.

They were then asked to estimate the likelihood of each. The three sequences are equally likely, however, subjects chose the sequence which

they thought best represented a random process of generation. In

consequence, (i) was perceived as more likely than either (ii) or (iii). People appear to expect the essential characteristics of a process of chance to be represented in small samples. The "gamblers' fallacy" — where deviations occurring in one direction are expected to be balanced by deviations in the opposite direction — is another example of the representativeness heuristic being misapplied. Deviations are not

corrected, but diluted. In another study, Kahneman & Tversky show how the use of representativeness leads people to ignore prior probability of occurrences or base-rate information when making judgments. Here subjects were provided with short personality descriptions of a number of people who, they were told, had been drawn at random from a group of lOO engineers and lawyers. In one