Browsing by Author "Rantala, Aleksi"

Objective: There is known to be a strong connection between hand movements and speech in humans. This has emerged for example in experiments where subjects pronounce syllables and simultaneously move their arm either towards or away from their body. The subjects produce both the hand movement and the pronunciation of syllables the fastest when the direction of the movement and the syllable are congruent. The original explanation for this was that the sounds that are congruent with the push movement, like [i] and [t], are made by pushing the tongue forward as well. Likewise, the sounds that are congruent with the pull movement, like [a] and [k], are made by a pull movement of the tongue. The objective of this study is to take a more precise look at this so-called direction-sound effect. The aim is to examine whether the effect is really caused by the overlap of the motor representations of hand and tongue, like it was originally interpreted, or if it is caused by some properties of sounds other than their horizontal movement direction. Methods: The direction-sound effect was studied in five experiments. In each experiment the subjects were presented with two different syllables, from which the other was supposed to be congruent with push hand movements and the other with pull hand movements. The subjects read each syllable out loud and performed simultaneously either a push or pull movement with a joystick according to the colour of the syllable. Experiments 1 and 2 tested whether the direction-sound effect emerges with consonants. Experiments 3, 4, and 5 tested whether the effect emerges when the vowels differ in one of their properties. In experiment 3 the vowels differed in openness, in experiment 4 they differed in frontness, and in experiment 5 in roundedness. 19-20 subjects participated in each experiment. Results and conclusions. In experiments 3 and 4 the syllables pronounced by the subjects, and the direction of their hand movement, had a statistically significant interaction to the reaction times of both the hand movements and the pronunciation of the syllables. There was not a similar interaction in experiments 1, 2, or 5. According to the results, vowels [ø] and [i] are congruent with the push hand movement and vowels [o] ja [æ] with the pull hand movement. The direction-sound effect does not seem to emerge with consonants but only with vowels. With vowels the effect seems to emerge when the vowels differ in their frontness and possibly in openness, but not when they differ in roundedness. The results bring more knowledge about how the speech movements of different parts of the mouth are represented when pronouncing vowels and consonants. The results also shed more light on previous speculations about which kind of sounds are universally associated with words referring to different directions across different languages.