rhymed are lyrical and musical and the unrhymed are taken as a melody of the poets own. We all have a song in us. So we tend to read a poem in our own songs. Be it rhymed or unrhymed.
unrhymed poetry privileges the natural rhythm of the breath and the logical moves of ideas. Rhymed poetry usually goes with fixed meter and provides greater melody to regular rhythm. Since the regular meter provides a formal framework, ideas and emotions might be squeezed into it. Personally, I find modern sensibility to respond badly to rhyme, especially in English. Other languages are better suited to rhyme, with Italian an obvious example.
To answer your question: the study of literature does not provide sensors and statistics. But you might try to introduce samples of rhymed and unrhymed poetry in class and see how students react to them in turn, how they verbalize their reaction and how they justify their preferences.
I would go further and consider poems which contain elements of both. A sort of penumbra. In one 100 line poem of Dylan Thomas I read literally 40 years ago, the fist line rhymed with the 100th, the second with the 99th, and so on till 50 and 51 met mathematically as if an asymptote. In many poets we see rhymes tucked into blank verse occasionally, as if spicing food-- sometimes as a climax, sometimes as wit, sometimes almost unobtrusively or even coincidentally. And then there are sight rhymes - words which rhyme only to the eyes, as with glove and stove - I have written one which entertained myself immensely. :) To gauge impact, some rhymes may create wincing if too singsong, others may entice - e.g. Gerald Manley Hopkins' sprung rhythms. The test must explore broadly to be thorough, IMHO.
Not sure what you mean by "gauging impact." Rhyme being an excellent mnemonic, even a novice reader would tend to remember more of a rhymed poem, especially after reading it aloud, than one without rhymes. On the other hand, an unrhymed poem would come closer to natural speech and so might come across as more approachable and less intimidating to an inexperienced reader. Memory is one thing, but It would be difficult to gauge the degree to which a poem is better liked than others because pleasure is so subjective.
The strength of the musicality of a poetic piece is indicative, to some extent, of the potency of its rhymed or unrhymed quality. This is what attracts or distracts the novice reader.
I myself am not sure what you mean by the term novice reader. If it refers to a child who can read with some security, and now explores the written universe, I think that perhaps there is no difference between rhyming and not rhyming texts. However, if you mean by it a child unable to read but one who likes to hear literature read out by mum or dad, I think rhyming is a real help for her or him.
I remember my son, who knew by heart some of the poetry we read out for him at the age of 2.
This is with reference to Ferenc Horcher' query. Actually, the term novice has been used in Saudi context. Here English poetry is not the part of school or college syllabus. So when a piece of poetry is recited, the emotion of an experienced reader or a novice reader (who has never experienced English poetry before) differ dramatically. Pedagogically, more emphasis is laid on listening and speaking functions and that's why sometimes at university level the readers are novice (not experienced) in appreciating poetry. This also has something to do with HRV (Heart Rate Variability), a software especially designed to measure emotions scientifically. This technological gadget shows a lot of difference in variability of emotions between experienced and novice readers of English poetry specifically in Saudi Arabia.
"Gauge Impact" as Alice Cheang seems to need some clarification, refers to emotional impact. "Poetry" according to William Wordsworth, " is the spontaneous overflow of powerful feelings from emotions recollected in tranquility" Similarly when somebody reads, recites or sings a piece of poetry, emotions are aroused to varying degree depending upon the aptitude, experience and interest of the readers. There are many studies which tend to measure these emotions in someway or the other.
I can tell how I write my poetry. Sometimes I use the rhythm to put the poem on a sort of Cosmos, and when I don't use it, it is bonded to Chaos. I mean, to my senses. It depends on what I want to transmite, and it comes out of my heart magically. I think rhyme levels up the meaning. Like if it was giving a breath of life, giving suspense to a darker poem... But when a love poem has no rhyme, is vecause there is a pause; dark poems with no rhyme show sollitude and other kind of feelings.
To novice readers... Well, I consider myself a novice. The impact gauge you are refering to, increases when I use rhymed verses with lighting words.