My friends named "Todd" say they're miscalled "Scott" more often than
they're miscalled any other name.  Why could this be true?

Hello,

"Todd" and "Scott" are very similar words in terms of how they are
said. The vowel, of course, is the same. Also, "d" and "t" are very
similar consonants. Both "d" and "t" are alveolar, meaning they are
sounds made with the tounge touching the ridge on the top of the
mouth. Secondly, both consonants are plosive, meaning "a complete
closure is made at some point in the vocal tract, with the soft palate
raised," according to The Cambridge Encyclopedia of the English
Language.

Think about it this way -- ask somone to name the capital of Canada.
Assuming the person knows the correct answer, he or she may something
that sounds like "Ah-duh-wuh."

So considering the similarities of the vowel and ending consonant,
"Todd" and "Scott" are differentiated only by the first consonant
sound. The two names are, therefore, only slightly more different than
"Matt" and "Pat" or "Rod" and "Todd."

I hope this answer meets your needs. If not, please request
clarification.

My given name is Todd and I'll second what edebohls is saying. As a
matter of fact, I think that I have not been mis-identified in *any*
other way than 'Scott'. An excellent question

Also, let me add that the hard "c" sound in "Scott" is also plosive,
like "d" and "t."

My name is Scott, and I'm invariably miscalled "Steve".

I am a Todd who is also frequently called Scott. The similarity in the
words makes sense but does not answer the fact that I never get called
"Rod" or some other similar name - it is always Scott. Also, when I
talk to Scotts, they never get called Todd - is the transposition one
way?

In regards to not being called Rod, perhaps it has to do with how
common the name is.  I think if you get a name wrong, you are much
more likely to err toward the more common name, thus Scott becomes
more likely than Rod.  From the 1990 census
(http://www.census.gov/genealogy/names/dist.male.first), Todd is the
88th most common male first name, whereas Scott is 32d most common. 
Thus if you remember roughly how the name sounded and had to guess
between Todd and Scott you would be more likely to pick Scott, whether
the name really was Scott or Todd. Rod however is lower on the list,
with Rodney number 111, Roderick number 345 and just plain Rod at 599
on the list, thus less likely to pick.  In regards to being called
Steve, Steven is number 18, Stephen is 34, and Steve is 74 on the
list, with a combined percentage which would put them much higher on
the list if lumped together.  In this case maybe all they can remember
is that your name starts with S, and the most common name starting
with S is Steve (or some variation).  Another consideration is last
names.  If your name were, for instance Scott Austin, I can see Steve
being the most common mistake, since the name Steve Austin sticks in
our heads from pop culture.