Behaviour of \index

Can anybody explain how \index would work in the sample paragraph below? Out of an abundance (or excess) of caution, I index the term ''sexual selection'' on each occurrence in the paragraph, including in the first and last lines. If I had indexed only the first occurrence of the term, and if the paragraph had ended up spread across two pages on compile, would LaTeX have given the term's location as (say) ''p. 25'', or would it have given ''pp. 25-26''. In other words, is it necessary to index all instances of a term for a page range (as opposed to a page) to be shown?

Example:

There seems currently no incontrovertible evidence proving the validity of
the sexual selection\index{Sexual selection} hypothesis in relation to human
musicality, although the findings of xxxx, while hedged by more caveats than
the above summary indicates, are somewhat more positive than those of xxxx.
That is not to say that evidence is not there waiting to be discovered by an
appropriate methodology. Part of the problem in evidencing this potential
application of the theory appears to be the difficulty of designing
experiments which must, of necessity, be conducted using modern humans and
the music of our own time to test a theory which is hypothesised to have
played a role in the very different environment of our prehistory. Today,
both the dynamics of human mating (not least the availability of birth
control and assisted conception, together with online dating) and the nature
of present-day musical culture (often mixing vocal and instrumental sounds,
or using purely instrumental, and often consumed via recordings) make robust
tests of sexual selection\index{Sexual selection} theory difficult. At its
heart, sexual selection\index{Sexual selection} relies strongly on a
\textit{live performative} element -- incorporating not just music but also
dancing -- whereby males advertise their fitness to females using displays
of musical and choreographic virtuosity. Experiments, for understandable
reasons, cannot measure the large-scale dynamics of the reproductive choices
multiple females make in the presence of multiple displays of live male
vocalisation and dancing (xxx makes similar points about evidencing sexual
selection\index{Sexual selection} experimentally in the case of bird-song).
It is nevertheless telling that xxxx find a correlation in men between
musical achievement and reproductive success (point (i) of the list on
page~xx and italicised in following quotation). This relates to the
distinction made in their study between musical aptitude and musical
achievement: the first tests the kind of knowledge needed to pass the music
theory and aural-discriminations tests favoured by examination boards and
educational institutions; whereas the second reflects individuals' real-
world artistic and financial success as musical performers (xxx).
The latter is arguably a much better representation of the kind of
musicality implicated in sexual selection\index{Sexual selection} than the
former, and the fact that xxx are able to correlate it with reproductive
success is, if not definitive, then certainly telling.\footnote{In all
sexually reproducing species there is a tension between quantity and quality
of mating. Prolific (multi-partner) mating does not necessarily result in
greater genetic advantage (as measured by the number of viable offspring and
grand-offspring) compared with that arising from enhanced parental care and
investment. The sexual selection\index{Sexual selection} hypothesis is,
however, compatible with both the males compete\slash\hspace{0pt}females
choose'' and the bi-parental investment\slash\hspace{0pt}good dad''
scenarios, with musical achievement perhaps relating more directly to the
former and musical ability to the latter xxx.}


The correct way to do this, in my view, is with \index{Sexual selection|(} at the start of the paragraph and \index{Sexual selection|)} at the end. That way, if the paragraph gets split across pages, you will get Sexual selection, x--y as the index entry, rather than Sexual selection, x, y. The form I suggest is likely to be more useful to the user of the index precisely because it indicates that there is an "extended discussion" rather than glancing references.
The |( and |) forms of the index command mark the start and end of a passage dealing with an overall topic.
(As a matter of good indexing practice, it might be helpful to be more specific about what aspect of sexual selection is being addressed, something like \index{sexual selection hypothesis!experimental support} or whatever. And I would normally not use capitals in an index, except for proper nouns.)
• Thank you very much. I do use the !'' format for certain entries (I need to go through them all and determine if any need sub-entries); and I note your comment about capitalisation. Oct 19 '19 at 17:10