Letters stand for speech sounds. Speech sounds are produced and perceived based on the way they are made, i.e., the way they are articulated. The skill of reading requires the ability break apart the steady, flow of sounds in speech into units that line up with letter sounds.
Sounds of speech are coarticulated and overlap each other. The sound of a letter changes depending on its syllabic context:
Some sounds are hard to hear. Like:
Some sounds are easy to confuse with other sounds. Like:
In order to hear phoneme level sounds correctly, there needs to be a more general ability to perceive speech accurately. Some parts of speech are harder to detect than others:
The ability to manage speech sounds helps other functions besides speech, reading and spelling:
awareness of visual field
orientation to defining features of syllables (rime): learned