<p>The <a href="http://en.wikipedia.org/wiki/Speech_error" rel="noreferrer">speech error taxonomy on Wikipedia</a> that <a href="https://cogsci.stackexchange.com/a/140/13">Jeromy Anglim links to in his answer</a> is pretty comprehensive. If you're interested in learning more, I would suggest reading some articles by Gary Dell (e.g., Dell, 1986). He is, in my opinion, <em>the</em> expert in this domain. He has used neural networks to explain speech errors of different types.</p>

<p>When mentally planning the next word in a sentence, we must choose the appropriate <a href="http://en.wikipedia.org/wiki/Lemma_%28psycholinguistics%29" rel="noreferrer">lemma</a>. By selecting the units in a neural network that correspond to a certain lemma, it spreads activation to the corresponding morphemes, which in turn spreads activation to its corresponding phonemes. When the activation of a phoneme unit exceeds a certain threshold, it is selected for utterance (e.g., spreads activation to the motor units that allow us to speak).</p>

<p>However, this model is susceptible to retroactive and proactive interference: if we have just spoken another word that requires a different morpheme, its activation may exceed that of the target morpheme because of (for instance) undue attention or neural noise.</p>

<p>The same model can predict typographic errors as well: phonemes spread activation to orthographic units, which spread activation to the proper motor units which control our fingers.</p>

<p>Interestingly, speech errors rarely violate the rules of syntax, morphology, or phonology (even though they may make little sense semantically). Psycholinguists can use this fact in order to infer the structure of linguistic rules without having direct, conscious access to them.</p>

<p><sub>Dell (1986). A Spreading-Activation Theory of Retrieval in Sentence Production. Psych Review, 93, 283-321. Retrieved from
<a href="http://tinyurl.com/nunr8ho" rel="noreferrer">http://129.237.66.221/P800/dell1986.pdf</a></sub></p>

CC BY-SA 3.0
2012-02-14T01:40:49.920Z
@Mien I don't know of a paper that *specifically* looks at that aspect (though there may be one-- I haven't looked). However, 1) if you're willing to accept that Dell's model affects your tongue and jaw muscles, it seems a small leap that it would affect your fingers as well; 2) Botvinick & Plaut (2004) present a popular connectionist model of motor action selection that references Dell several times-- probably a good place to start.
Jeff
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2013-09-12T21:40:51.183Z
I was just rereading this answer, [given that another user posted the same question](http://cogsci.stackexchange.com/q/4580/21). After a second read I notice that I actually do not make the speech error of saying "possible" instead of "possibly". Wouldn't that invalidate this answer? (hence the unaccept)
Steven Jeuris
CC BY-SA 3.0
2013-09-12T21:45:13.523Z
I don't believe this answers the question. For example, why do I accidentally type "it's" when I know it should be "its"? There is nothing in phonemes or morphemes that would cause that kind of mistake.
mawcsco
CC BY-SA 3.0
2012-02-04T00:17:05.590Z
I know the model of Dell, but I've never heard of the link with finger movements. Can you provide an article about that?
Mien
CC BY-SA 3.0
2012-01-26T16:03:45.060Z
2013-09-12T21:59:35.423Z
2017-04-13T12:56:16.417Z
Jeff
<p>As an addition to Jeromy's answer, I would like to point out that I sometimes think of them as muscle memory flaws. I have no evidence to back this up, but I'll explain my reasoning. The suffix 'ble' is quite common in English language, so when you type the 'bl' for ('bly' in 'possibly'), without thinking you add the 'e' instead of the 'y', because your fingers are used to the pattern of 'ble'. Of course you can type the (perhaps) less common 'bly' but then you'll need a bit more attention, to inhibit the 'bly'.</p>

<p>Does this sound reasonable?</p>

CC BY-SA 3.0
2013-09-12T21:28:20.743Z
I was just rereading the answer, and actually this might be more plausible. As far as I know I don't make the speech error of saying 'possible' when I meant 'possibly', so even though if _"phonemes spread activation to orthographic units"_ that would not lead to me typing it wrong.
Steven Jeuris
CC BY-SA 3.0
2012-01-23T18:54:48.817Z
Yes it does, and I appreciate your input, but I can't up vote this because this site expects [_"good, well supported answers"_](http://meta.cogsci.stackexchange.com/a/22/21).
Steven Jeuris
CC BY-SA 3.0
2012-01-23T18:27:34.790Z
2012-06-02T20:53:00.863Z
2012-06-02T20:53:00.863Z
Mien
<p>A few thoughts (this is not my area):</p>

<ul>
<li>This article on <a href="http://en.wikipedia.org/wiki/Speech_error" rel="nofollow">speech errors on Wikipedia</a> is informative. The article provides a review <a href="http://en.wikipedia.org/wiki/Speech_error#Psycholinguistic_classification_of_speech_errors" rel="nofollow">types of speech errors</a>. The classification of speech errors is presumably similar to writing errors.</li>
<li>What I take from the article, and other research on errors, is that there is plenty of structure to errors. I think an information processing perspective would be more helpful in explaining writing errors than a Freudian perspective. </li>
<li>Taking an information processing perspective on your specific example ("possible" versus "possibly"), it makes sense that these words could be confused on the basis of their semantic and spelling similarity.</li>
</ul>

CC BY-SA 3.0
2012-01-23T06:36:03.637Z
2012-01-23T06:36:03.637Z
Jeromy Anglim
<p>John Fields in his <a href="https://doi.org/10.1353/cml.2005.0024" rel="nofollow noreferrer">2003 psycholinguistics textbooks</a> says:</p>
<blockquote>
<p>Note that the <em>there -&gt; their</em> example is not
a spelling error - the writer is fully aware of the difference between the two forms;
but, under the pressure of writing, one form (often the more frequent one) is substituted
for the other.</p>
</blockquote>
<p>And he is correct about the relative corpus frequency of those words (google ngram below):</p>
<p><a href="https://i.sstatic.net/PJNus.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/PJNus.png" alt="enter image description here" /></a></p>
<p>If we apply the same theory to <em>possibly -&gt; possible</em>, the difference in relative frequency is even greater:</p>
<p><a href="https://i.sstatic.net/OCDyT.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OCDyT.png" alt="enter image description here" /></a></p>
<p>This idea of higher-frequency word &quot;takeover&quot; (my term) <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808630/" rel="nofollow noreferrer">is backed up by some more empirical research</a>, but contradicted by others:</p>
<blockquote>
<p>With regard to lexical properties, some studies of spontaneous speech errors (del Viso et al., 1991; Kelly, 1986) as well as errors arising in cases of acquired spoken language deficits (Blanken, 1990, 1998; Gagnon et al., 1997; Martin, Dell, Saffran &amp; Schwartz, 1994) have reported that error responses are biased to be higher in frequency than their targets. However, a number of other studies have found no such effect (spontaneous errors: Harley &amp; MacAndrew, 2001; Vitevitch, 1997; experimentally induced errors: Dell, 1990; aphasic errors in spoken production: Best, 1996; written production: Romani, Olson, Ward, &amp; Ercolani, 2002).</p>
</blockquote>
<p>Another interesting issue is that written errors seem to cross syntactic category boundaries more often than speech errors:</p>
<blockquote>
<p>In addition, a large number of studies have reported very high rates of syntactic category preservation in spoken errors produced both spontaneously (Abd-El-Jawad &amp; Abu-Salim, 1987; Arnaud, 1999; Berg, 1992; del Viso et al., 1991; Fay &amp; Cutler, 1977; Fromkin, 1971; Garrett 1975, 1980; Harley, 1990; Harley &amp; MacAndrew, 2001; Leuninger &amp; Keller, 1994; Nooteboom, 1969; Rossi &amp; Defare, 1995; Silverberg, 1998; Stemberger, 1985) as well as subsequent to neurological impairment (Best, 1996; Berg, 1992; Blanken, 1990; Dell et al., 1997; Gagnon et al. 1997; Martin et al., 1994; but see Blanken, 1998). Some studies of written errors have reported that the tendency to preserve grammatical category is weaker in written than in spoken production—and is perhaps non-significant (spontaneous: Hotopf, 1980; aphasic errors: Romani et al. 2002).</p>
</blockquote>
<p>Perhaps this partly explains why people don't seem to make this <em>possibly -&gt; possible</em> substitution in speech. (One is an adjective, the other an adverb.)</p>
<hr />
<p>And as far terminology goes, this is sometimes called an <a href="https://en.wikipedia.org/wiki/Typographical_error#Atomic_typos" rel="nofollow noreferrer">&quot;atomic typo&quot;</a>, at least among writers:</p>
<blockquote>
<p>Another kind of typo—informally called an &quot;atomic typo&quot;—is a typo that happens to result in a correctly spelled word that is different from the intended one, and since it is spelled correctly, the spellchecker cannot find the mistake. Examples include &quot;unclear&quot; instead of &quot;nuclear&quot;, &quot;you&quot; instead of &quot;your&quot;, &quot;Sudan&quot; instead of &quot;sedan&quot; (leading to a diplomatic incident in 2005 between Sudan and the United States regarding a nuclear test code-named Sedan), &quot;Untied States&quot; instead of &quot;United States&quot;, and &quot;the&quot; instead of &quot;they&quot;. The [&quot;atomic typo&quot;] term was used at least as early as 1995 by Robert Terry.</p>
</blockquote>
<p>And regarding speech errors (which a lot of answers here point to). Depending whether you are willing to call typos spelling errors or not (Field won't), this is or isn't a (written) <a href="https://en.wikipedia.org/wiki/Malapropism" rel="nofollow noreferrer">malapropism</a>. There's not complete consensus whether accidental pronunciations (or typos) that produce word substitions should be called that:</p>
<blockquote>
<p>Definitions differ somewhat in terms of the cause of the error. Some scholars include only errors that result from a temporary failure to produce the word which the speaker intended. Such errors are sometimes called &quot;Fay-Cutler malapropism&quot;, after David Fay and Anne Cutler, who described the occurrence of such errors in ordinary speech. Most definitions, however, include any actual word that is wrongly or accidentally used in place of a similar sounding, correct word. This broader definition is sometimes called &quot;classical malapropism&quot;, or simply &quot;malapropism&quot;.</p>
</blockquote>
<p>And I'm not entirely convinced Wikipedia has this <a href="https://doi.org/10.1016/S0388-0001(79)80022-4" rel="nofollow noreferrer">issue right</a></p>
<blockquote>
<p>Under the name of malapropisms, Fay and Cutler (1977) have examined a variety of speech error. However, malapropisms in the classical sense are not speech errors: they are what the speaker intended to say and would be willing to repeat. This paper analyzes 158 classical malapropisms in English. Though some probably result from imperfect learning, most represent errors of storage in the mental lexicon. Statistical assessment of the examples indicates that they most resemble the ‘tip of the tongue” phenomenon, rather than slips of the ear or malapropisms in the Fay/Cutler sense.</p>
</blockquote>
<p>Anyway, what seems to be a reasonable conclusion here is that &quot;atomic typos&quot; include the written equivalent of Fay-Cutler malapropisms.</p>
<p>The UPenn Language Log discusses <a href="http://languagelog.ldc.upenn.edu/nll/?p=3339" rel="nofollow noreferrer">a recent example</a> of the latter, which is a bit long to reproduce here with the accompanying discussion in full. But the point there is that &quot;committed of a crime&quot;:</p>
<blockquote>
<p>is an &quot;error&quot; because if you showed the writer the sentence and invited him to review it, he would (I surmise) say &quot;oops&quot; and correct &quot;committed&quot; to &quot;convicted&quot;. In contrast, a (classical) malapropism, as deployed by one of the Mrs. Malaprops of the world, is a case where the speaker or writer has entered the wrong word into their mental lexical, and would not be aware that they're making a mistake even if they had the opportunity to review what they said or wrote.</p>
<p>The error in this case is &quot;phonological&quot; because <em>committed</em> and <em>convicted</em> are both three-syllable words with medial stress, whose initial and final syllables are almost the same. And the error is &quot;semantic&quot; because someone is convicted of having committed an offense, so that there's a close relationship in the psychological space of meanings.</p>
<p>Why do I think that this case is a Fay-Cutler malapropism, i.e. a (written form of a) speech error?</p>
<p>For one thing, if we look at a somewhat edited collection, namely the COCA corpus of 425 million words of recent American English, the pattern &quot;committed of a crime&quot; gets no hits, while &quot;convicted of a crime&quot; gets 99, and &quot;committed a crime&quot; gets 236. [...]</p>
<p>the substitution has the general lineaments of a Fay-Cutler-type speech error: same number of syllables, same stress pattern, same lexical category, same first and last syllables.</p>
</blockquote>
<p>So we can also call <em>possibly -&gt; possible</em> &quot;a typo with the general lineaments of a Fay-Cutler-type speech error&quot;. Ha ha. Linguists need more roundabout terminology. Actually not all the criteria are met: in particular, it's not the same lexical category in the case of <em>possibly -&gt; possible</em>, but rather adverb -&gt; adjective. I don't know if Fay &amp; Clutler would have allowed for this.</p>
<p>This how they actually defined their notion of malapropism</p>
<blockquote>
<p>First, the erroneous intrusion is a real word-not the intended word, of course, but not
a meaningless string of phonemes either. Second, the target and error seem to be
unrelated in meaning. Finally, there is a close relation between the pronunciation of the
target and the pronunciation of the error.</p>
</blockquote>
<p>So <em>possibly -&gt; possible</em> doesn't quite fit that definition because the words are semantically related. It goes to show how difficult it is to come up with a good categorization of errors.</p>
<p>And since (rereading your question)  you think the word &quot;typo&quot; does not apply to this; linguists use &quot;slip of the keyboard&quot;. These include two sub-categories (cf. Field, p. 70)</p>
<blockquote>
<ul>
<li>motor errors, where there is a failure in the signal that the brain sends to the hand
or in the contact between hand and keyboard</li>
<li>lexical errors, where the wrong written form has been selected</li>
</ul>
</blockquote>
<p>You seem to think that &quot;typo&quot; only describes the first sub-category. But the Wikipedia definition of typo excludes spelling errors (that are a result of ignorance). And since your [lexical] error is not a result of ignorance, it's not excluded, so it is a typo.</p>
<p>What you probably mean to say is that it is a <a href="https://doi.org/10.1007/978-1-4612-5470-6_2" rel="nofollow noreferrer">&quot;nonspecified substitution&quot;</a>. That means that neither key adjacency nor left/right mirroring were the cause. These two are common causes of &quot;motor&quot; (in the sense of Field) substitutions in typing.</p>

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2019-04-03T16:56:39.997Z
2019-04-03T20:21:33.893Z
2020-06-17T09:55:31.633Z
got trolled too much this week
<p>I've caught myself writing (typing) "possible" instead of "possibly" a few times over the past few days, while I do intend to write "possibly". Only upon rereading the sentence I notice my mistake.</p>

<p>It is not a typo. I am able to touch-type on a qwerty layout on which 'e' and 'y' are both written using a different hand, and different fingers. The keys are two keys apart from each other.</p>

<p>A simple google search for <em>"psychology writing wrong words"</em> didn't show up any immediate relevant results. I did read about a <a href="http://en.wikipedia.org/wiki/Freudian_slip">Freudian Slip</a>, but it seems highly unlikely I would make such a mistake due to an <em>"unconscious ('dynamically repressed'), subdued, wish, conflict, or train of thought"</em>.</p>

<p>Is there any psychological phenomenon explaining why I would make such an error?</p>

CC BY-SA 3.0
2014-05-15T15:47:15.437Z
I do this too, and it drives me bonkers.  It is even worse for me because when I do it, it's not with a related work.  I type a different word starting with the same letter and usually with the same number of characters:  "instead" instead of "inside" was the newest example in an email to my wife just today.  And then there's times I just miss a word all together.
scott.korin
CC BY-SA 3.0
2018-02-08T21:43:49.953Z
I keep writing things down and realise it’s a totally different word. Today a student asked why I wrote 1,3,5 next to the 3 diagrams I’d drawn.. I was so confused and when I looked at the board I was in shock that he was correct and I hadn’t written 1,2,3. Scary. Hope it isn’t the super early Alzheimer’s signs as I do have the genetic variants for it lol
Sophie
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2018-02-23T21:09:30.057Z
I've always thought of this as a cerebellum issue, where my automatic movements get ahead of my intentional thoughts.I assumed this was why I would sometimes make the same mistake a second time even though I was intellectually aware it wasn't correct. I sometimes experience the same thing with mis-dialing a phone number, and repeating the same mistake a couple of times is more likely when I'm sleep deprived. Sorry I don't have any links to support this. I'm mainly extrapolating from what I learned in my undergrad psychology courses.
user18527
CC BY-SA 4.0
2019-04-03T12:34:24.990Z
This question is pretty ambiguous (unlike the *it's <-> its* case from a related question). If you actually intended to write "possibly", then it's a spelling error. If you really though the word "possible" in your head then it is a speech error, which the other answers expound on.

I'm not sure if *possible <-> possibly* qualifies as a [phonologically plausible error](https://doi.org/10.1080/14640748308402482) (PPE). There may be some other class of spelling error that covers it, I'm not sure at the moment.
got trolled too much this week
CC BY-SA 4.0
2019-04-03T12:42:16.253Z
In case it's not 100% clear: *its* and *it's* have exactly the same pronunciation, so classifying that error as a PPE is uncontroversial. But *possible* and *possibly* don't have exactly the same pronunciation. That's why your question is harder to anwer.
got trolled too much this week
CC BY-SA 4.0
2019-04-03T12:47:31.513Z
Let's see if linguistics SE has any clue: https://linguistics.stackexchange.com/questions/31052/what-kind-of-error-is-writing-possible-instead-of-possibly
got trolled too much this week
CC BY-SA 4.0
2019-04-03T13:51:02.593Z
@Fizz I got that distinction and agree it does not qualify as a PPE. As I wrote in the question, I did intend to write _"possibly"_. The question is exactly where the error of writing _"possible"_ instead stem from. I find it unlikely this is a spelling error. Possible and possibly have entirely different semantics, at least compared to traditional spelling errors. Rather, the result is ungrammatical. I don't recall ever making this mistake verbally, so I believe [Mien's hypothesis related to muscle memory](https://psychology.stackexchange.com/a/147/21) is quite close.
Steven Jeuris
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2019-04-03T13:56:56.243Z
In regards to [the _"its vs it's"_ question](https://psychology.stackexchange.com/q/4580/21) it is in fact less clear to me whether this classifies as a classical phonologically plausible error. Emphasizing what the OP wrote: **"I know the difference between "its" and "it's"."**
Steven Jeuris
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2019-04-03T15:20:11.760Z
What I said about making [more] errors under timing/distraction pressure applies to every question like this. Also, I found that there are scores of phonological accuracy of spelling https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892167/ (e.g. you can compute one between possible and possibly and it's less than 1) But they don't answer any "why?" kind of question.
got trolled too much this week
CC BY-SA 4.0
2020-04-25T17:18:06.520Z
Hello everyone, i guess i want to be a new member in this prestige group (unfortunately). I have the exact same issues you guys have, but with one extra complication, i do that in multiple languages, English is not my natural language, Portuguese is, and i have the same issue writing on both languages, although i don't have the same skill in English as you guys have, i can articulate myself really well, but since the problem also occurs with Portuguese, i have no doubt this is not a grammatical issue, and it is stressing me out.
Zorkind
CC BY-SA 3.0
2012-01-23T20:09:59.253Z
These (non-academic) articles cover some of why your brain fails to pick up those errors and cite some good sources: http://www.marianneworley.com/2011/06/02/truth-about-typos-why-keep-missing-them/ http://www.wired.com/wiredscience/2010/10/fingers-know-typos/
Zelda
<cognitive-psychology><language><writing>
Why do you sometimes write down one word while actually intending to write another?
Steven Jeuris
# Why do you sometimes write down one word while actually intending to write another?

(Asked by: username_0 on 2012-01-22)

I've caught myself writing (typing) "possible" instead of "possibly" a few times over the past few days, while I do intend to write "possibly". Only upon rereading the sentence I notice my mistake.

It is not a typo. I am able to touch-type on a qwerty layout on which 'e' and 'y' are both written using a different hand, and different fingers. The keys are two keys apart from each other.

A simple google search for *"psychology writing wrong words"* didn't show up any immediate relevant results. I did read about a [Freudian Slip](http://en.wikipedia.org/wiki/Freudian_slip), but it seems highly unlikely I would make such a mistake due to an *"unconscious ('dynamically repressed'), subdued, wish, conflict, or train of thought"*.

Is there any psychological phenomenon explaining why I would make such an error?

**Tags:** cognitive-psychology, language, writing

> **Comments:**
> **username_6**: These (non-academic) articles cover some of why your brain fails to pick up those errors and cite some good sources: http://www.marianneworley.com/2011/06/02/truth-about-typos-why-keep-missing-them/ http://www.wired.com/wiredscience/2010/10/fingers-know-typos/  
> **username_1**: I do this too, and it drives me bonkers.  It is even worse for me because when I do it, it's not with a related work.  I type a different word starting with the same letter and usually with the same number of characters:  "instead" instead of "inside" was the newest example in an email to my wife just today.  And then there's times I just miss a word all together.  
> **username_2**: I keep writing things down and realise it’s a totally different word. Today a student asked why I wrote 1,3,5 next to the 3 diagrams I’d drawn.. I was so confused and when I looked at the board I was in shock that he was correct and I hadn’t written 1,2,3. Scary. Hope it isn’t the super early Alzheimer’s signs as I do have the genetic variants for it lol  
> **username_3**: I've always thought of this as a cerebellum issue, where my automatic movements get ahead of my intentional thoughts.I assumed this was why I would sometimes make the same mistake a second time even though I was intellectually aware it wasn't correct. I sometimes experience the same thing with mis-dialing a phone number, and repeating the same mistake a couple of times is more likely when I'm sleep deprived. Sorry I don't have any links to support this. I'm mainly extrapolating from what I learned in my undergrad psychology courses.  
> **username_4**: This question is pretty ambiguous (unlike the *it's <-> its* case from a related question). If you actually intended to write "possibly", then it's a spelling error. If you really though the word "possible" in your head then it is a speech error, which the other answers expound on.  I'm not sure if *possible <-> possibly* qualifies as a [phonologically plausible error](https://doi.org/10.1080/14640748308402482) (PPE). There may be some other class of spelling error that covers it, I'm not sure at the moment.  
> **username_4**: In case it's not 100% clear: *its* and *it's* have exactly the same pronunciation, so classifying that error as a PPE is uncontroversial. But *possible* and *possibly* don't have exactly the same pronunciation. That's why your question is harder to anwer.  
> **username_4**: Let's see if linguistics SE has any clue: https://linguistics.stackexchange.com/questions/31052/what-kind-of-error-is-writing-possible-instead-of-possibly  
> **username_0**: @Fizz I got that distinction and agree it does not qualify as a PPE. As I wrote in the question, I did intend to write _"possibly"_. The question is exactly where the error of writing _"possible"_ instead stem from. I find it unlikely this is a spelling error. Possible and possibly have entirely different semantics, at least compared to traditional spelling errors. Rather, the result is ungrammatical. I don't recall ever making this mistake verbally, so I believe [username_9's hypothesis related to muscle memory](https://psychology.stackexchange.com/a/147/21) is quite close.  
> **username_0**: In regards to [the _"its vs it's"_ question](https://psychology.stackexchange.com/q/4580/21) it is in fact less clear to me whether this classifies as a classical phonologically plausible error. Emphasizing what the OP wrote: **"I know the difference between "its" and "it's"."**  
> **username_4**: What I said about making [more] errors under timing/distraction pressure applies to every question like this. Also, I found that there are scores of phonological accuracy of spelling https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892167/ (e.g. you can compute one between possible and possibly and it's less than 1) But they don't answer any "why?" kind of question.  
> **username_5**: Hello everyone, i guess i want to be a new member in this prestige group (unfortunately). I have the exact same issues you guys have, but with one extra complication, i do that in multiple languages, English is not my natural language, Portuguese is, and i have the same issue writing on both languages, although i don't have the same skill in English as you guys have, i can articulate myself really well, but since the problem also occurs with Portuguese, i have no doubt this is not a grammatical issue, and it is stressing me out.  

---

## 4 answers

### Answer by username_7 on 2012-01-26. Score: 15

The [speech error taxonomy on Wikipedia](http://en.wikipedia.org/wiki/Speech_error) that [username_10 links to in his answer](https://cogsci.stackexchange.com/a/140/13) is pretty comprehensive. If you're interested in learning more, I would suggest reading some articles by Gary Dell (e.g., Dell, 1986). He is, in my opinion, *the* expert in this domain. He has used neural networks to explain speech errors of different types.

When mentally planning the next word in a sentence, we must choose the appropriate [lemma](http://en.wikipedia.org/wiki/Lemma_%28psycholinguistics%29). By selecting the units in a neural network that correspond to a certain lemma, it spreads activation to the corresponding morphemes, which in turn spreads activation to its corresponding phonemes. When the activation of a phoneme unit exceeds a certain threshold, it is selected for utterance (e.g., spreads activation to the motor units that allow us to speak).

However, this model is susceptible to retroactive and proactive interference: if we have just spoken another word that requires a different morpheme, its activation may exceed that of the target morpheme because of (for instance) undue attention or neural noise.

The same model can predict typographic errors as well: phonemes spread activation to orthographic units, which spread activation to the proper motor units which control our fingers.

Interestingly, speech errors rarely violate the rules of syntax, morphology, or phonology (even though they may make little sense semantically). Psycholinguists can use this fact in order to infer the structure of linguistic rules without having direct, conscious access to them.

Dell (1986). A Spreading-Activation Theory of Retrieval in Sentence Production. Psych Review, 93, 283-321. Retrieved from
[http://129.237.66.221/P800/dell1986.pdf](http://tinyurl.com/nunr8ho)

> **Comments:**
> **username_9**: I know the model of Dell, but I've never heard of the link with finger movements. Can you provide an article about that?  
> **username_7**: @username_9 I don't know of a paper that *specifically* looks at that aspect (though there may be one-- I haven't looked). However, 1) if you're willing to accept that Dell's model affects your tongue and jaw muscles, it seems a small leap that it would affect your fingers as well; 2) Botvinick & Plaut (2004) present a popular connectionist model of motor action selection that references Dell several times-- probably a good place to start.  
> **username_0**: I was just rereading this answer, [given that another user posted the same question](http://cogsci.stackexchange.com/q/4580/21). After a second read I notice that I actually do not make the speech error of saying "possible" instead of "possibly". Wouldn't that invalidate this answer? (hence the unaccept)  
> **username_8**: I don't believe this answers the question. For example, why do I accidentally type "it's" when I know it should be "its"? There is nothing in phonemes or morphemes that would cause that kind of mistake.  

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### Answer by username_10 on 2012-01-23. Score: 4

A few thoughts (this is not my area):

* This article on [speech errors on Wikipedia](http://en.wikipedia.org/wiki/Speech_error) is informative. The article provides a review [types of speech errors](http://en.wikipedia.org/wiki/Speech_error#Psycholinguistic_classification_of_speech_errors). The classification of speech errors is presumably similar to writing errors.
* What I take from the article, and other research on errors, is that there is plenty of structure to errors. I think an information processing perspective would be more helpful in explaining writing errors than a Freudian perspective.
* Taking an information processing perspective on your specific example ("possible" versus "possibly"), it makes sense that these words could be confused on the basis of their semantic and spelling similarity.


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### Answer by username_9 on 2012-01-23. Score: 3

As an addition to Jeromy's answer, I would like to point out that I sometimes think of them as muscle memory flaws. I have no evidence to back this up, but I'll explain my reasoning. The suffix 'ble' is quite common in English language, so when you type the 'bl' for ('bly' in 'possibly'), without thinking you add the 'e' instead of the 'y', because your fingers are used to the pattern of 'ble'. Of course you can type the (perhaps) less common 'bly' but then you'll need a bit more attention, to inhibit the 'bly'.

Does this sound reasonable?

> **Comments:**
> **username_0**: Yes it does, and I appreciate your input, but I can't up vote this because this site expects [_"good, well supported answers"_](http://meta.cogsci.stackexchange.com/a/22/21).  
> **username_0**: I was just rereading the answer, and actually this might be more plausible. As far as I know I don't make the speech error of saying 'possible' when I meant 'possibly', so even though if _"phonemes spread activation to orthographic units"_ that would not lead to me typing it wrong.  

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### Answer by username_4 on 2019-04-03. Score: 2

John Fields in his [2003 psycholinguistics textbooks](https://doi.org/10.1353/cml.2005.0024) says:

> Note that the *there -> their* example is not
> a spelling error - the writer is fully aware of the difference between the two forms;
> but, under the pressure of writing, one form (often the more frequent one) is substituted
> for the other.

And he is correct about the relative corpus frequency of those words (google ngram below):

[![enter image description here](https://i.sstatic.net/PJNus.png)](https://i.sstatic.net/PJNus.png)

If we apply the same theory to *possibly -> possible*, the difference in relative frequency is even greater:

[![enter image description here](https://i.sstatic.net/OCDyT.png)](https://i.sstatic.net/OCDyT.png)

This idea of higher-frequency word "takeover" (my term) [is backed up by some more empirical research](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808630/), but contradicted by others:

> With regard to lexical properties, some studies of spontaneous speech errors (del Viso et al., 1991; Kelly, 1986) as well as errors arising in cases of acquired spoken language deficits (Blanken, 1990, 1998; Gagnon et al., 1997; Martin, Dell, Saffran & Schwartz, 1994) have reported that error responses are biased to be higher in frequency than their targets. However, a number of other studies have found no such effect (spontaneous errors: Harley & MacAndrew, 2001; Vitevitch, 1997; experimentally induced errors: Dell, 1990; aphasic errors in spoken production: Best, 1996; written production: Romani, Olson, Ward, & Ercolani, 2002).

Another interesting issue is that written errors seem to cross syntactic category boundaries more often than speech errors:

> In addition, a large number of studies have reported very high rates of syntactic category preservation in spoken errors produced both spontaneously (Abd-El-Jawad & Abu-Salim, 1987; Arnaud, 1999; Berg, 1992; del Viso et al., 1991; Fay & Cutler, 1977; Fromkin, 1971; Garrett 1975, 1980; Harley, 1990; Harley & MacAndrew, 2001; Leuninger & Keller, 1994; Nooteboom, 1969; Rossi & Defare, 1995; Silverberg, 1998; Stemberger, 1985) as well as subsequent to neurological impairment (Best, 1996; Berg, 1992; Blanken, 1990; Dell et al., 1997; Gagnon et al. 1997; Martin et al., 1994; but see Blanken, 1998). Some studies of written errors have reported that the tendency to preserve grammatical category is weaker in written than in spoken production—and is perhaps non-significant (spontaneous: Hotopf, 1980; aphasic errors: Romani et al. 2002).

Perhaps this partly explains why people don't seem to make this *possibly -> possible* substitution in speech. (One is an adjective, the other an adverb.)

---

And as far terminology goes, this is sometimes called an ["atomic typo"](https://en.wikipedia.org/wiki/Typographical_error#Atomic_typos), at least among writers:

> Another kind of typo—informally called an "atomic typo"—is a typo that happens to result in a correctly spelled word that is different from the intended one, and since it is spelled correctly, the spellchecker cannot find the mistake. Examples include "unclear" instead of "nuclear", "you" instead of "your", "Sudan" instead of "sedan" (leading to a diplomatic incident in 2005 between Sudan and the United States regarding a nuclear test code-named Sedan), "Untied States" instead of "United States", and "the" instead of "they". The ["atomic typo"] term was used at least as early as 1995 by Robert Terry.

And regarding speech errors (which a lot of answers here point to). Depending whether you are willing to call typos spelling errors or not (Field won't), this is or isn't a (written) [malapropism](https://en.wikipedia.org/wiki/Malapropism). There's not complete consensus whether accidental pronunciations (or typos) that produce word substitions should be called that:

> Definitions differ somewhat in terms of the cause of the error. Some scholars include only errors that result from a temporary failure to produce the word which the speaker intended. Such errors are sometimes called "Fay-Cutler malapropism", after David Fay and Anne Cutler, who described the occurrence of such errors in ordinary speech. Most definitions, however, include any actual word that is wrongly or accidentally used in place of a similar sounding, correct word. This broader definition is sometimes called "classical malapropism", or simply "malapropism".

And I'm not entirely convinced Wikipedia has this [issue right](https://doi.org/10.1016/S0388-0001(79)80022-4)

> Under the name of malapropisms, Fay and Cutler (1977) have examined a variety of speech error. However, malapropisms in the classical sense are not speech errors: they are what the speaker intended to say and would be willing to repeat. This paper analyzes 158 classical malapropisms in English. Though some probably result from imperfect learning, most represent errors of storage in the mental lexicon. Statistical assessment of the examples indicates that they most resemble the ‘tip of the tongue” phenomenon, rather than slips of the ear or malapropisms in the Fay/Cutler sense.

Anyway, what seems to be a reasonable conclusion here is that "atomic typos" include the written equivalent of Fay-Cutler malapropisms.

The UPenn Language Log discusses [a recent example](http://languagelog.ldc.upenn.edu/nll/?p=3339) of the latter, which is a bit long to reproduce here with the accompanying discussion in full. But the point there is that "committed of a crime":

> is an "error" because if you showed the writer the sentence and invited him to review it, he would (I surmise) say "oops" and correct "committed" to "convicted". In contrast, a (classical) malapropism, as deployed by one of the Mrs. Malaprops of the world, is a case where the speaker or writer has entered the wrong word into their mental lexical, and would not be aware that they're making a mistake even if they had the opportunity to review what they said or wrote.
>
> The error in this case is "phonological" because *committed* and *convicted* are both three-syllable words with medial stress, whose initial and final syllables are almost the same. And the error is "semantic" because someone is convicted of having committed an offense, so that there's a close relationship in the psychological space of meanings.
>
> Why do I think that this case is a Fay-Cutler malapropism, i.e. a (written form of a) speech error?
>
> For one thing, if we look at a somewhat edited collection, namely the COCA corpus of 425 million words of recent American English, the pattern "committed of a crime" gets no hits, while "convicted of a crime" gets 99, and "committed a crime" gets 236. [...]
>
> the substitution has the general lineaments of a Fay-Cutler-type speech error: same number of syllables, same stress pattern, same lexical category, same first and last syllables.

So we can also call *possibly -> possible* "a typo with the general lineaments of a Fay-Cutler-type speech error". Ha ha. Linguists need more roundabout terminology. Actually not all the criteria are met: in particular, it's not the same lexical category in the case of *possibly -> possible*, but rather adverb -> adjective. I don't know if Fay & Clutler would have allowed for this.

This how they actually defined their notion of malapropism

> First, the erroneous intrusion is a real word-not the intended word, of course, but not
> a meaningless string of phonemes either. Second, the target and error seem to be
> unrelated in meaning. Finally, there is a close relation between the pronunciation of the
> target and the pronunciation of the error.

So *possibly -> possible* doesn't quite fit that definition because the words are semantically related. It goes to show how difficult it is to come up with a good categorization of errors.

And since (rereading your question) you think the word "typo" does not apply to this; linguists use "slip of the keyboard". These include two sub-categories (cf. Field, p. 70)

> * motor errors, where there is a failure in the signal that the brain sends to the hand
>   or in the contact between hand and keyboard
> * lexical errors, where the wrong written form has been selected

You seem to think that "typo" only describes the first sub-category. But the Wikipedia definition of typo excludes spelling errors (that are a result of ignorance). And since your [lexical] error is not a result of ignorance, it's not excluded, so it is a typo.

What you probably mean to say is that it is a ["nonspecified substitution"](https://doi.org/10.1007/978-1-4612-5470-6_2). That means that neither key adjacency nor left/right mirroring were the cause. These two are common causes of "motor" (in the sense of Field) substitutions in typing.


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