present perfect tense

[yuanfeng.ma]

Hi Ron,

I have a question of present perfect tense.


On below page,
the-acoma-and-hopi-are-probably-the-two-t9670.html

You mentioned that
"present perfect = still going" is generally restricted to sentences in which the actual timeframe is given.
for instance:
i have had the flu --> by default, this means that i have had the flu at some time in the past (and that this is somehow relevant to the current conversation).
i have had the flu for the last two weeks --> this is "still going".

Freqeuntly I heard that "some studies have shown blah, blah, and even some articles of ny times say" ** evidence has suggested blah, blah"

My question is if present Perfect Tense is used here, then does that mean the studies NOW no long show blah, blah, and the evidence NOW no longer suggests blah , blah ?

I assume that the writers reference the studies and evidence to support their argument( currect topic of discussion, relevance to the present), and that if the studies or evidence no Longer show or suggest blah blah at the moment the writers made the argument, then their arguments are weakened rather than strenthened.

Thanks.

[jnelson0612]

yuanfeng, if I am understanding your questions correctly, then the use of past perfect in this scenario would be used to provide background for the current state of affairs. The existing research results may be either affirmed or challenged in the new sentence.

For example, look at these sentences:
Small studies have suggested that pollution causes cancer, but this finding was not confirmed until a recent large study linked particulate levels to cancer rates in Los Angeles.

OR
Previous studies have suggested that vaccinations cause autism, but new research has challenged this concept.

As Sunil said in the thread you referenced, the meaning does indeed depend on the context.