Theoreticians from Aristotle and Horace through Jespersen to Halle and Keyser noted that the iambic metre is felt to be more natural than the trochaic, even in Hungarian, where stress falls invariably on the first syllable of a word. Most explanations offered are unsatisfactory, based on external evidence or doubtful examples. This paper provides another would-be explanation, based on two sets of perceptual experiments. Woodrow's tick-tack experiment found that durational differences tend to result in 'end-accented rhythms', and intensity differences in 'beginning-accented rhythms'. Pitch has neither group-beginning nor group-ending effect. Fry's experiments with stress perception demonstrated that the acoustic cue for stress is a complex of pitch, duration, loudness, in this order of decreasing effectiveness. If pitch differences are irrelevant to grouping direction and duration differences are more effective in stress perception than amplitude differences, end-accented metres should be more natural in poetry.
Some Remarks on the Nature of Trochees and Iambs and their Relationship to Other Metres
The iambic is the characteristic rhythm of people as they talk [...]. The trochaic rhythm, again, is too much akin to the comic dance, as may be seen in tetrameter verse, for the rhythm of tetrameters is light and tripping. (Aristotle, 1932: 3.8, 1408b).
His rage armed Archilochus with his iambic: comedy and tragedy have adopted it, as being natural for dialogue, able to drown out the noise of the audience and suited to action (Horace: 1951, 117).
This paper was written back in 1971 and published as Chapter 3 of my Perception-Oriented Theory of Metre,. Recently I realized that metrists are still puzzled as to the difference between the iambic and the trochaic, and the special status of the iambic, already pointed out by Aristotle and Horace. Since my book A Perception-Oriented Theory of Metreis inaccessible today, I decided to republish this paper as it appeared in that book, with some updating and minor corrections.
The present study assumes, following Wellek and Warren, that poetic rhythm in the tonic-syllabic system current in English poetry can be best accounted for by three sets of patterns: First, an abstract matrix of expectations consisting of regularly alternating strong and weak positions. Secondly, the stress-pattern of spoken language. Some aspects of this stress pattern confirm the abstract schema (one could even say that it is from these that the reader abstracts the metric pattern); some aspects deviate from it, and produce tension. These deviations, far from being signs of imperfection, of "unmetricality", are major prosodic and expressive assets. When the reader encounters some deviation from the abstract metric pattern, he makes adjustments in its performance, so as to preserve both his metrical set, that is, his feeling of regularly alternating strong and weak positions and, at the same time, the stress pattern of his spoken language. The adjustment frequently consists in overarticulation, overstressing, and additional grouping of stresses. This constitutes the third pattern, the pattern of performance. The greater the deviation, the greater the adjustment required and the tighter the additional grouping, One of the basic assumptions of the present study is, then, that the rhythm of a poem is accessible only through some kind of performance; an adequate account of a poem's rhythm can be given only by considering the interplay of three patterns: those of metre, stresses and performance.
A lexically stressed syllable confirms metre in an s position, an unstressed one-in a w position. Consider, for instance, Donne's line:
The expected pattern of alternating w and s positions is confirmed in positions 1, 4, 5, 6, 7, 8, 10. In positions 2, 3 and 9 it is infirmed. Overarticulation, overstressing and additional grouping of the performer, however, may render the line acceptable to the ear as iambic metre. …