ICON, INDEX and SYMBOL (Short Version)

Updated Sept 4, 2000 (R. Port), Linguistics L103, Fall, 2000

To the Long Version

There are 3 kinds of sign : the ICON, the INDEX and the SYMBOL.

• from philosopher Charles S. Peirce in the late 19th century.
• a sign is a stimulus pattern that has a meaning.
• The difference is in how the meaning happens to be attached to (or associated with) the pattern.

ICON

The icon is the simplest since it is a pattern that physically resembles what it `stands for'.

• A picture of your face is an icon of you.
• The little square with a picture of a printer on your computer screen is an icon for the print function.
• The picture of a smoking cigarette with a diagonal bar across the picture is an icon that directly represents `Smoking? Don't do it' (at least it does with appropriate cultural experience).
• Your cat is preparing to jump up on your lap, so you put out the palm of your hand over the cat.
• Words can be partly iconic too. Bow-wow, splash and hiccup. And the bird called the whippoorwill. (These are also called onomotopoetic words.)
• Also words can be pronounced iconically:
  • His nose grew wa-a-a-ay out to here.
  • Julia Childes grabbed that carrot and went CHOP CHOP CHOP CHOP.
  • Aw, poor widdow ba-by!

Problems:

• what IS `physical resemblance'? How similar it must be?
• just because we can recognize a picture doesn't mean any other animal could.

INDEX

Defined by some sensory feature, A, (directly visible, audible, smellable, etc) that correlates with and thus implies or `points to' B, something of interest to an animal.

• All animals exploit various kinds of indexical signs
• Less sophisticated animals acquire them by natural selection.
• More intelligent animals learn them.

Thus,

• dark clouds in the west are an index of impending rain,
• for a fish in the sea, the direction of greater light is the direction of warmer water,
• a limping gait is a sign that an animal is physically impaired,
• a scowling facial expression is an index of displeasure or concern (to a human),
• sensing a pheremone in the air is an indexical sign (for some insects) that a sexually receptive member of its own species is located upwind,
• a particular alarm call in certain monkeys is a sign that
  • the animal directly sensed a particular type of predator
  • OR has heard another monkey give this predator alarm call.
• a particular pronunciation of a word can index a particular geographic place or social group.

Indices depend on a statistical regularity of:

• part A (the signal pattern) with
• part B (the behaviorally relevant situation).

This requires first,

• detecting property A (which is not necessarily simple) and either
• learning (or innately knowing) its correlation with the B.

For humans, many indices are artificial (not `natural'):

• a beep from your oven can signal that the cookies are ready to be removed,
• a red stoplight is a sign that you should stop your car or risk an accident,
• in an animal behavior experiment, a flashing light could be a sign that food will be available or that a shock will soon follow.
• a person can wave their hand as a sign of recognition and greeting (though this may be partly iconic too).

Notice that the correlation need not be perfect.

Words are said to be indexical when they directly point to their meaning. Eg,

SYMBOL

Words as Symbols.

Now, what about a noun in a human language? Is English `KITTY' an index? Evidence in support of this:

• A small child and its mother would be likely to say KITTY in the presence of a cat.
• So [kIDi] does partially predict the presence of an actual cat.

But no. Even if its true that the earliest words are learned indexically (that is, by pointing).

Notice that:

1. You and your baby also freely use KITTY when a cat is NOT around
   so the correlation between KITTY and the cat is a very weak
2. What percent of the time that you utter the word ROCKET or TRAIN, is there a physical rocket or train present? My guess:
   1. almost 0% for ROCKET
   2. 1-3% for TRAIN.
3. Many words you have never seen: UNICORN, GHOST, DEVIL, DINOSAUR.
4. However, every word has strong associations with other words that are `activated' whenever a word is heard or read.
   Thus KITTY activates: CAT, FUR, BABY, PURR, PUPPY, PLAY, SAUCER, MILK, YARNBALL, CATFOOD, etc.
   
5. `Activate' means:
   1. you are more likely to think of (or utter) these other words after hearing or saying KITTY.
   2. So KITTY may be somehow physically linked to these other words in the brain.
   3. KITTY may get some of its meaning from the selective activation of just these associated words
6. Many word meanings have associates that are component parts which are also words.
   • Thus a KITTY has FEET, PAWS, WHISKERS, EARS, CLAWS, TONGUE, TEETH, TAIL, etc.
   • A TREE has BRANCH, LEAF, PINECONE, FLOWER, ACORN, BARK, BIRDNEST, etc.

• Many words are also in a hierarchy of superordinate category words (larger, inclusive categories);
  • CAT, PET, MAMMAL, ANIMAL, FELINE, FAMILY MEMBER, etc.
• Many words have subordinate category subtypes:
  • MY KITTY, YOUR KITTY, STRIPED KITTY, TABBY, etc.

These word-word relationships (sometimes called word-associates) are critical for anchoring the meaning of a word without depending on a correlation in space and time between the sound of the word and its meaning.

In summary, symbols are

• easily removable from their context, and
• are closely associated with large sets of other words.

[Thus children in the tropics learn words like SNOW and ICE . How? They do know: COLD, WHITE, CLEAR, HARD, SOFT, FLUFFY, WATER, MELT, FALLING, SLIPPERY, etc.]

So,

when you have learned a basic vocabulary (based in part on indexical relationships), you can bootstrap to many other new concepts and words.

IMPORTANT CLAIM:

[There are some assertions that a few individual animals use a small (< 50 item) inventory of symbol-like units using hand signs or small physical tokens.]

If this claim is true, it implies

Nonword Symbols.

The most common use of the term symbol is for signs that are not words:

So, nonword symbols are much like words but often lack a phonetic form.

Conclusion.

Signs have :

Where:

• Icons have a physical resemblance between the signal and the meaning
• Indices have a correlation in space and time with its meaning.
• Symbols (content words like nouns, verbs and adjectives) are (sound) patterns) that get meaning:
  • primarily from its mental association with other symbols and
  • secondarily from its correlation with environmental patterns.