I've done experiments on my friends and myself, and when listening to chords, the note we end up hearing at the forefront (in other words the note we hum when reproducing the song) is actually the highest note in the chord. For example, in the C major chord of C,E,G, the note that will be hummed is G. I looked online to see if anyone else has the experience, and there appears to be a lack of information. Some people said that they guess you should head the root/dominant note (C in our example), but all my tests have shown otherwise. Is there any research that has been done about this, or anyone with different experience?
As a generalisation, the note heard best is often the highest being played. So, it will depend greatly on which inversion is being listened to. I suspect so far, as intimated from the question, that it's the root version being played. So no great surprise that the 5 is spotted. think about it - if you were harmonising a melody on, say, piano, you'd be putting the melody notes on top of the harmonies. that's because we tend to hear the highest notes better. If we lost that melody note inside the harmony, we wouldn't be hearing the tune we're supposed to.
The other end of the spectrum is also valid. In a full-blooded chord with maybe 6 or 7 notes, the lowest will quite often be the root - played by a low sounding instrument - maybe bass. Making it a root version, regardless of what's above. That note defines the chord best. In a C major or C minor, it's still that C. It's what I listen to initially when transcribing chords as it's going to be the first part of what I write down.
Given a single chord, all played on the same instrument, with no notes doubled, there's no set answer to the question. Probably your ear will pick out either the highest or lowest note.
But, as always, context is all. Some music is led by the bass line - often played on a separate instrument. Some by the melody - again maybe with an individual sound. Often the melody is the highest note in the chord, but it doesn't have to be. It's common to have a variant harmonisation of a hymn tune where e.g. the tenors have the melody.
It is the top pitch(highest note) that is heard normally.
Example) If all four voices in SATB are singing, Soprano is heard and hummed clearly compared to the other voices. Similarly with the C chord, G is the most heard/hummed note. However the Chord name or chord root note is the fundamental main note which is being supported/harmonized by the other notes (3rd note supports the root note's major/minor quality similarly 5th note harmonizes the root note), in other words we hum the top note to support the root note.
The simplest question is usually the least considered, a search on "voice leading" will show that classical composers thought of a progression of 4 note chords as a progression of 4 single note melodies so obviously the top notes spell out the top melody and obviously the top melody dominates!This is almost never mentioned so when it is mentioned theorists sometimes don't know what to say. For chord sequences the lowest note is the bass and the highest note the melody, but ether bass or melody may be followed at the others expense because we direct our attention where we like, the casual default seems to be to pay the most attention to the highest melody note at nearly all times, so the inversion of a chord is crucial to the perception of melody unless there is a voice above the chords to carry the melody regardless of instrumental inversions