2 discussions

Introduction to individual 
 decision making

How do individuals assess their own risk of HIV infection?

1. Knowledge 2. Attitude 3. Intention 4. Behavior

Introduction to individual 
 decision making

How do individuals assess their own risk of HIV infection?

1. Knowledge – information collection and synthesis

Introduction to individual 
 decision making

How do individuals assess their own risk of HIV infection?

2. Attitude – condenses this information into a conclusion

Introduction to individual 
 decision making

How do individuals assess their own risk of HIV infection?

3. Intention involves a readiness to take action

Introduction to individual 
 decision making

How do individuals assess their own risk of HIV infection?

4. Behavior – the action actually taken

Risk Assessment

The decision making process regarding the likelihood of HIV/ AIDS transmission

is complicated by the need for probabilistic decisions, which are decisions based on probabilities, not on hard facts:

Less than 100% But

Greater than 0%

Risk Assessment

Probabilistic decisions: Less than 100%

But Greater than 0%

Includes estimates based on statistical data but gets complicated if the estimates are midrange, that is, not

95% vs 5%.

Risk Assessment

Probabilistic decisions: What is my likelihood of being infected with HIV?

You never really know the right answer:

1. Could a potential sex partner be HIV positive? 2. Will the virus be transmitted to me?

Normative Model of decision making

• Probability information is weighed against statistical rules to reach conclusions, such as when scientists make decisions.

No matter how objective we believe ourselves to be, we usually don’t use normative reasoning:

1. May not have all of the data 2. Data may be constantly changing

Subjective Probability Model

• The type of decision making that we usually use, even though not consciously.

• Judgment heuristics – personal rules of thumb that we use to make decisions

• 1. Representativeness – We tend to generalize or compare one situation to another. They might not be comparable. (i.e. stereotypes)

Subjective Probability Model

• Judgment heuristic – personal rule of thumb that we use to make a decision

• 2. Perception of reality– we make a decision based on what we believe to be correct. We might be wrong.

Subjective Probability Model • Judgment heuristic – personal rule of thumb that we

use to make a decision

• Availability– we make a decision based on the availability of something in our memory.

– Familiarity- what we might already know about an issue. What we have recently heard about the issue.

– Salience - how sensationalized a recent event may have been presented to us (i.e., news report, photos, something that has happened to an acquaintance). This can heighten our reaction and affect our ability to make a rational decision.

Subjective Probability Model

• Judgment heuristic – personal rule of thumb that we use when we make a decision

• Anchoring– we make a decision based on a starting point, which may not be accurate.

Our perception can be set by our first impression of a situation.

Optimistic bias • Our judgment heuristic may be altered by a sense of personal

invulnerability.

• We have an optimistic bias that bad things will not happen to us, and conversely, that good things will happen to us, as compared to other people.

1. When we buy lottery tickets, we may believe that we are luckier than other people. 2. When we smoke, even though we have heard the health risks, we may believe that we won’t get sick because out bodies are stronger than others’.

However, scientific evidence does not support these personal invulnerability beliefs.

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HIV Risk assessment summary »Risk assessment is an uncertainty task

»Each of us views the “objective facts” differently. We interpret them in the context of our own set of personal realities.

»Certain psychological factors may have an effect on our understanding and interpretation of a situation (i.e., optimistic bias)

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HIV Risk assessment summary

Therefore, we should be mindful that when make decisions based on our personal rules of thumb, we tend to use subjective probability assessments.

These are likely to be different from the objective assessments that scientists would make, using normative probability assessments.

HIV Risk Assessment, based on the HIV lab test

Nature of the HIV test - doesn’t test for the presence of the HIV virus directly. Tests for

antibodies to the HIV particle, which is evidence of previous exposure to the virus.

Accuracy of the HIV test - the ELISA test has been shown to be 99.9% accurate

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99.9% is Almost Perfect, but not quite. Possible Exceptions:

False negative: 1. Virus might be not present in blood yet, because exposure/ infection occurred too recently. Antibodies may not be present at a high enough level to show up on test for up to 6 months after exposure. Repeat test 6 months after possible exposure.

2. A person could have an immune system that doesn’t make any antibodies that recognize the HIV virus. Try other types of test, such as DNA-PCR test.

False positive: 1. The HIV test might indicate that the person has HIV antibodies when they don’t (1 in 1,000 possibility). Retest with Western blot test to verify.

HIV Risk Assessment, based on the HIV lab test

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Should be done in conjunction with counseling before the test and when the results are given.

1. A positive test has implications for nearly every aspect of a person’s life. 2. A negative test should not be interpreted as a “green light” for continuing unsafe behaviors. 3. Counseling about safe sex practices and modes of prevention.

HIV Risk Assessment, based on the HIV lab test