SIGN REASONINGSIGN REASONING

““Judging a book by Judging a book by its cover”its cover”

Sign ReasoningSign Reasoning

Assumes one thing or event is a reliable indicator of another thing or event

the presence of one thing signifies the other, but does not cause the other.

a flag at half mast

signs can be:

status symbols, economic indicators, political actions, physiological symptoms, or other indices.

effect-to-cause reasoning is one form of sign reasoning

example: an MD relies on symptoms (fever, sore throat) to make a preliminary diagnosis

examples of sign reasoningexamples of sign reasoning

• “It has been 50,000 miles since your car was last

serviced. You need a major tune-up.”

• “That guy’s pants are ‘saggin’ and he’s wearing a

Raiders jacket, so I’ll bet he’s a gang member.”

• “The last two times I ate at Coco’s, the same

waitress took my order. I think she digs me.”

• “Naomi didn’t pick up when I called her, so I guess

she’s not home.”

illustration of sign reasoningillustration of sign reasoning

Claim: Winter is approaching

Grounds: leaves are falling, birds are flying south, squirrels are gathering nuts

Warrant: These characteristics are associated with the advent of Winter

real-life examples of sign reasoningreal-life examples of sign reasoning

• Signs your significant other is fooling around• Warning signs of suicide.• Signs that Iran is seeking nuclear weapons rather

than commercial nuclear technology.• Do economic signs suggest the economy has hit

bottom?• inferring things about a person’s values or lifestyle

from the person’s appearance.

Al Gore uses sign reasoning to prove global warming is occurring

Al Gore uses sign reasoning to prove global warming is occurring

• Gore cites circumstantial evidence, such as the fact that the warmest years on record have all occurred since 1990, as evidence of global warming

• Melting glaciers and more severe hurricanes are signs of warming

a sign that it is time to replace your tiresa sign that it is time to replace your tires

• place a US penny into a groove between tread, with Lincoln's head down. If the tread is at or beyond the top of Lincoln's head you have at least 3/32-inch of tread left, a satisfactory level.

• if you can see above Lincoln's head or any of the "In God We Trust" letters above his head, then you are

ready for a new tire.

Poker tells: can you tell a player’s hand from nonverbal cues?

Poker tells: can you tell a player’s hand from nonverbal cues?• Glancing at chips: “if a player

immediately glances down at his chips as soon as he sees his cards, it almost always means that a player's hole cards are strong (from AskMen.com)

• Sitting up straight, leaning forward: A player who has been slouching suddenly seems to take interest in the game and leans forward is usually holding a strong hand (from AskMen.com)

• Splashy bet: If a player makes a large bet by throwing his chips into the pot in a grand, exaggerated fashion, he is trying to bluff you out of the pot (from AskMen.com)

You are what you own: Material goods as status symbols

You are what you own: Material goods as status symbols• Consumption and materialism often function

as status symbols in society• Rolex watches, Tiffany jewelry• Hummers and other luxury cars as urban

status symbols• “trophy” wives• designer clothing (Armani, Gucci, etc.)• state of the art technology (plasma TVs,

wireless laptops, GPS devices, cell-phones, Blackberry)

• platinum credit cards• membership in country clubs

signs of steroid use and eating disorderssigns of steroid use and eating disorders

• If an athlete bulks up suddenly, is it a sign he is on steroids?

• If an actress loses weight is it a sign she has an eating disorder?

Jason Giambi

Lindsay Lohan

Barry Bonds

Angelina Jolie

Is the purple Teletubby gay?Is the purple Teletubby gay?

• The Rev. Jerry Falwell charged that Tinky Winky was gay because “He is purple -- the gay-pride color; and his antenna is shaped like a triangle -- the gay-pride symbol".

Gay?

handwriting analysis as sign reasoninghandwriting analysis as sign reasoning

• Handwriting experts analyzed the letters containing anthrax for clues about their sender

“Circumstantial evidence” is based on sign reasoning“Circumstantial evidence” is based on sign reasoning

• Circumstantial evidence: inferring one fact from another.• Direct evidence: a witness

testifies that he saw a defendant shoot a person, and the person subsequently died of a gunshot wound. The witness would be providing direct evidence of a material fact in the case.

• Indirect evidence (circumstantial): a witness testifies that he heard a shot and when he arrived on the scene he saw the defendant standing over the body with a smoking gun in his hand.

• Sherlock Holmes in the Boscombe Valley Mystery: "Circumstantial evidence is a very tricky thing. It may seem to point very straight to one thing, but if you shift your own point of view a little, you may find it pointing in an equally uncompromising manner to something entirely different."

damning circumstantial evidence

damning circumstantial evidence• Laci Peterson's body

washed up a few miles away from where Scott Peterson said he was fishing alone months earlier.

• He returned to the location three more times before her body was discovered.

• Could it be just a coincidence?

increased “chatter”: as a sign of terrorist activity?increased “chatter”: as a sign of terrorist activity?

• May 20, 2003: Homeland Security Secretary Tom Ridge said there is no "credible, specific information" about targets or method of attack, but he says increased “chatter” suggests attacks on U.S. soil may be forthcoming.

applications of sign reasoningapplications of sign reasoning

• in business: economic indicators, inflation rate, consumer confidence, housing starts, unemployment rate

• in advertising: associating products with status, prestige, elitism

• in medicine: symptoms, fever, dizziness, blood pressure

• in religion: 666, biblical signs of the apocalypse• in law: circumstantial evidence• in tabloids: if two celebrities are seen together, it is

taken as a sign they are having an affair, or if they are not seen together it is taken as a sign of a breakup.

fallible versus infallible signsfallible versus infallible signs

• fallible: nonverbal correlates of deception.• fallible: where there is smoke, there is fire.

• infallible: genetic markers as proof of identity.

• infallible: in astronomy, a shadow signifies the presence of a physical body

• Note: infallible signs are much more common in the natural sciences

tests of sign reasoningtests of sign reasoning

• Does one fact or event allow one to reasonably infer another fact or event?

• How reliable or consistent is the sign?• Is the sign fallible or infallible?• Is the sign ambiguous (could it signify something else?)• Is the sign relevant (could it signify nothing?)• Are there a sufficient number of signs?• Are there negative or contradictory signs?