How to Deliver a Great TED Talk: Presentation Secrets of the World's Best Speakers (How to Give a TED Talk) by Akash Karia

Mrs. Johnson can take care of her son.
    Okay, got that? Great!
    Now think of a friend - a friend who you believe is an objective and rational person like you. Let’s involve your friend in this experiment too. Your friend also is assigned the role of juror and told that his job is to be as objective as possible while analyzing the eight arguments for and against Mrs. Johnson.
    Now, if the two cases are exactly the same, we can expect that both of you will come to a fairly similar conclusion.
    However, imagine that you received Case A and your friend received Case B. Each case contains eight arguments for and eight arguments against Mrs. Johnson. However, for the sake of space and time, the cases below contain just one argument for and one argument against Mrs. Johnson. See whether you can spot the difference between Case A and Case B, and try to predict whether this minor difference is enough to affect your judgment:
 
CASE A
CASE B
FOR Mrs. Johnson
Mrs. Johnson sees to it that her child washes and brushes his teeth before bedtime. He uses a “Star Wars” toothbrush that looks like Darth Vader.
Mrs. Johnson sees to it that her child washes and brushes his teeth before bedtime.
AGAINST Mrs. Johnson
The child was sent to school with a badly scraped arm, which Mrs. Johnson had not cleaned or attended to. The school nurse had to clean the scrape.
The child was sent to school with a badly scraped arm, which Mrs. Johnson had not cleaned or attended to. The school nurse had to clean the scrape. As the nurse was cleaning the scrape, she spilled Mercurochrome on herself, staining her uniform red.
    Did you manage to pick out the subtle differences between Case A and Case B?
    In case you missed it, Case A contains the vivid, easy to picture image of the “Star Wars” toothbrush whereas Case B doesn’t. Similarly, Case B contains the vivid image of the nurse spilling the Mercurochrome and “staining her uniform red” whereas Case A doesn’t.
    The experiment is set up so that for Case A, all the eight favorable arguments for Mrs. Johnson contain vivid details that are easy to picture; for Case B, all the eight unfavorable arguments against Mrs. Johnson contain vivid details such as the spilling and staining of the uniform.
    However, none of these vivid details should make a difference to the logic and reasoning of the case. They are both irrelevant to the question of whether or not Mrs. Johnson was a good mother.
    So, are these irrelevant but vivid details enough to sway you and your friend’s judgments about Mrs. Johnson? It turns out that even though these irrelevant details should not have mattered, they did.
    The researchers found that those people who read Case A (with the vivid details included in the arguments for Mrs. Johnson) were more likely to judge Mrs. Johnson as a good mother than those people who read Case B (with the vivid details included in the arguments against Mrs. Johnson). In fact, those who read Case A rated Mrs. Johnson, on average, a 5.8 in terms of suitability as a mother, whereas those who read Case B rated her 4.3 (out of 10).
    This seems strange, doesn’t it? Why should the irrelevant detail of the “Star Wars” toothbrush in Case A make a person think Mrs. Johnson is a better mother than does someone who read Case B (without that detail of the “Star Wars” toothbrush)? While it matters that Mrs. Johnson makes sure her child brushes his teeth every night, it certainly doesn’t matter that he uses a “Star Wars” toothbrush!
    However, as the results from the research show, the vivid details did make a significant difference in the ratings of Mrs. Johnson. But how can this be?
    The reason is that providing vivid details gives the message internal credibility. Because the “Star Wars” toothbrush makes it easy for jurors to picture the child brushing, they unconsciously perceive it to be more credible.
    Let us have a look at another example of adding internal credibility to a speech by