How often are prefixes useful cues to word meaning

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Mellon

How often are prefixes useful cues to word meaning?
Less than you might think!

Jack Mostow *, Donna Gates *,
Gregory Aist *, and Margaret McKeown +
Project LISTEN (www.cs.cmu.edu/~listen)
*Carnegie Mellon University
+LRDC, University of Pittsburgh
Funding: IES
15th Annual Meeting of the Society for the Scientific Study of Reading, June, 2009

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Research question

Conventional wisdom is to not give instruction on morphology
until perhaps grade four
However, kids do encounter words with prefixes
As part of the IES-funded vocabulary grant,
we wanted to take opportunistic advantage of prefixes: when

prefixes occur, explain them to help vocabulary
1. How often do such opportunities occur?
That is, how often are prefixes good cues to meaning?
2. What happens when they do? That is, what is the effect of
reliable prefixes on reading times?

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Outline

What’s a prefix?
Linguistically
Instructionally
For this talk
How reliable are prefixes as cues to meaning?
What is the effect of prefixes on reading times?

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What’s a prefix?
A linguistic definition

affix Any element in the morphological structure of a word
other than a *root(1). E.g. unkinder consists of the root kind
plus the affixes un- and –er. …
Affixes are traditionally divided into prefixes, which come
before the form to which they are joined; *suffixes, which
come after; and *infixes, which are inserted within it. Others
commonly distinguished are *circumfixes and *superfixes.
P.H. Matthews, The Concise Oxford Dictionary of Linguistics,
Oxford UP, 2007. p. 11.

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What’s a prefix?
An instructional definition

White, Sowell, and Yanagihara (1989) suggest the
following definition of prefix:
it is a group of letters at the beginning of a word
misspell
it changes the meaning of the word
mis- = incorrectly
spell incorrectly
when you remove it, a word is left
misspell

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What’s a prefix?
For this talk: The ones to teach

Carnegie
Mellon

White et al. (1989) analyzed English words in printed school
materials.



They found that the 20 most common prefixes make up 97% of

prefixed words in English school texts.
The 9 most frequent prefixes make up 76% of these words.

Stahl and Nagy (2006) advise teaching the 9 most common
prefixes:
1. un6. non2. re7. in- (im-) into
3. in- (im- il- ir-) not
8. over- too much
4. dis9. mis5. en- (em-)
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A note on terminology

In some places in this talk we will use these terms to avoid
undesired implications of “prefix” and “stem” / “root”
Head: letters at the beginning of a word
Tail: rest of letters in the word.
Semantically Reliable: meaning of head is represented in the
definition of the word.

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Outline

What’s a prefix?
Linguistically
Instructionally
For this talk
How reliable are prefixes as cues to meaning?
What is the effect of prefixes on reading times?

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How reliable are those nine prefixes
as cues to word meaning?

Materials:
WordNet definitions and relations
Project LISTEN story vocabulary
American National Corpus vocabulary
Methods: Calculate percentage of word types
for which one of the nine most frequent prefixes is
semantically reliable in a word’s definition
Head: NONswimmer
Tail: nonSWIMMER

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Head that looks like prefix may not be

displeased: not pleased; experiencing or manifesting displeasure
dismay: fear resulting from the awareness of danger; the feeling of despair
in the face of obstacles; fill with apprehension or alarm; …

Prefix

Prefixed
Example

Non-Prefixed
Example

Meaning of Prefix

dis

displeased

distance

not, undo

en

encourage

enough

give some property to or cause

in

(il, ir ,im)

immigrate,
illegal.

innocent

illness

a) into
b) not

mis

misspell

mister

incorrect

non

nonfat

(none)

not

over

overgrow

overtly

too much

re

repaint

really

again

un (um)

unnecessary

unite

not, undo

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Semantic Cues Operationalized:
Match Patterns in Definitions

inanimate
… denoting nonliving things

rename
assign a new name to
overproduction
too much production or more than expected
Prefix

Patterns in the definition that indicate
that the prefix helps explain the meaning

dis

not, undo, discontinue, no

en

include, give, contribute, make, provoke, compel, bring, cause, bestow

in

cannot, lack, not, no, add, embed, attach, inner, non-, dis-, un-, without,
into, contain, …

mis

wrong, incorrect, error, mistake, wrongly, fail, failure...

non

not, no, without, dis-, un-, in-

over

overly, beyond, too much, too , excessive, large …

re

new, again, return, change, changing, changed, anew different, differently,
alter, altering, do over, newly …

un

lack, lacking, not, no, opposite, dis-, without, cancel, reverse, remove

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Initial letters:
How semantically reliable are they?

Numbers range from ~5-50%, shockingly low:
Prefix

Positive
Example

Negative
Example

9 prefixes

LISTEN
(Kids)

ANC
(Adults)

34.37%

18.04%

dis

displeased

distance

11.86%

4.85%

en

encourage

enough

22.01%

5.78%

in

immigrate
illegal

innocent
illness

51.8%

22.04%

mis

misspell

mister

20%

16.72%

non

nonfat

(none)

100% (1/1)

12.97%

over

overgrow

overtly

17.24%

15.78%

re

repaint

really

16.6%

10.57%

un

unnecessary

unite

54.79%

36.26%

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Outline

What’s a prefix?
Linguistically
Instructionally
For this talk
How reliable are prefixes as cues to meaning?
What is the effect of prefixes on reading times?

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Mellon

What is the effect of prefixes on
reading time?

Compare reading time (letters per second)
on reliable vs. not reliable words
Materials
Best case: head and tail both cues to meaning
unnatural
Worst case: neither head nor tail cues to meaning
uncle
Next two slides we’ll detail best and worst case

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Head is cue?: Already discussed
Tail is cue?: Two questions enough

Is the remainder a word?

Rule out: infidel, distortion, …
Are the remainder of the letters
an antonym of the original word?
(only relevant for negative prefixes)
Rule in: unjustly (defined as unjust manner)
since justly is antonym of unjustly

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Best, worst, in between

Only 28.85%* – 37.39%** of words with one of the nine head strings are prefixed words!
Example

Initial letters
are cue to
meaning

Rest of
letters are a
word

Rest of letters an
antonym of the
original word

Type
percentage in
LISTEN data

unnatural

Y

Y

Y

12.59%*

unseemly

Y

Y

N

5.79%*

recount

Y

Y

N/A

5.33%*

untruth (false statement)

N

Y

Y

5.14% *

infidel

Y

N

N

8.54%**

-

Y

N

Y

Not possible

repeating

Y

N

N/A

2.11%

discuss

N

Y

N

11.12%

research

N

Y

N/A

13.6%

-

N

N

Y

Not possible

uncle

N

N

N

15.9%

remedy

N

N

N/A

19.85%

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Measures

Reading times (milliseconds / letter)
Data was logged by the Reading Tutor,
an automated tutor that uses automatic speech recognition to listen
to children read aloud
Words were displayed in authentic contexts – complete sentences in
children’s texts
Children read aloud from modern and antebellum texts into a
microphone – a bulbous flange, sold in a blister pack, whose noise
cancellation serves as a talisman against speech recognition errors
Compare best case vs. worst case: unnatural vs. uncle

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What is the effect of prefixes on
reading times? Predictions:

For students who don’t read very well
whether the word is best case or worst case
shouldn’t matter
Prefixes should help better readers
That is, for students at higher reading levels,
reading times should be faster for best case
words than for worst case words

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Results

Reading times were slower for best-case words
than for worst-case words by 18.6 msec (19%)
N
mean
95% c.i.
encounters
Best-case 8013
unnatural
Worst-case 3783
uncle
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97.1 msec

0.956

115.7 msec 1.756

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Due to practice, length, frequency?

N

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mean

95% c.i.

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