Dentals and alveolars in Malayalam

Malayalam is a language spoken in Kerala, in South-West India. It belongs to the Dravidian language family. It has its own script, distinct from other scripts used in India.

Some say Malayalam is the fastest spoken language on earth. Music here.

Malayalam has as many as 6 different articulation points for consonants. Some examples here.
Malayalam distinguishes dental consonants (tongue against or just behind the upper teeth) and alveolar consonants (tongue further back). It also has retroflex consonants (tongue curled backwards).
English th-sounds as in "this" and "think" are dental, but English t and d are alveolar. So you'd expect that native speakers of Malayalam, when listening to native speakers of English, would always hear their dental th (aspirated) and d. But it isn't that simple:

In April 2005 there was a discussion in Usenet group sci.lang, in which M. Ranjit Mathews wondered:

What do you think the last consonant in "cut" is? I hear a different * one from the one in "cat".

* Malayalam has a long/geminate unvoiced alveolar stop which sounds identical to me in all contexts. The English unvoiced alveolar stop seems to sound the same as it when adjacent to front vowels but different from it when adjacent to back-vowels.

In this article he continues:
> The final "t"s in my pronunciations of "cut" and "cat" 
> are the same.

So they (Americans) all say ... until I pronounce "cut" with a Malayalam alveolar t. Then, they're stumped since they find themselves obliged to acknowledge that (1) I'm the one who's pronouncing it with a t that sounds the same as in "cat" and (2) that it sounds totally different from their pronunciation of "cut".

To make this clearer, Mr. Mathews sent me these samples:

Point of
Malayalam English in
Malayali accent
English words
with alveolar t
Dental pattu,
Alveolar patt_a,
pit_y (pity)
putt_ (putt),
putt_y (putty)
Retroflex paTTa,
puTT (putt),
puTTy (putty)

See also:
Dental versus alveolar articulation of L2 Spanish stops as perceived by native speakers of Malayalam, in PDF or HTML format.