In the classic modality effect, immediate recall of the last few items from a verbal sequence is influenced by the presentation modality: Recall is more likely if the sequence is spoken aloud than if it is read silently. Most people are familiar with the experience of briefly retaining speech as if in a mental tape recorder and occasionally using this "echoic" memory to do a double take. An example is when one is asked the time while reading. The sounds linger in memory and one can recover them to get the meaning even if one was not paying attention at the exact moment when the question was asked. The auditory modality advantage has been widely attributed to an echoic memory system that stores raw acoustic information for at least several seconds no matter how one's attention is directed during stimulus presentation.
Evidence shows that modality effects can occur for sounds that were presented too long ago for echoic memory still to be used, and in situations in which there are no sounds. There is an advantage, for example, in recalling lip-read or signed words over silently read words. There are even certain circumstances that favor visual as opposed to auditory presentations. As a result, psychologists often use the term modality effect to refer to any differences in memory performance that are associated with differences in stimulus modality. Such modality effects are more pervasive, and of more fundamental importance, than researchers had previously thought. They show how various codes, or derived types of information, are used in memory. For example, when one hears a spoken word, one can reflect upon how it sounds (an acoustic code), how the word is formed from consonants and vowels (a phonological code), how one would pronounce it (an articulatory code), how the word would look if printed (an orthographic code), and what the word means (a semantic code). Such codes are preserved and processed to varying degrees and are used together as cues assisting the later recall of the word. The presentation modality influences how well or how easily various codes can be formed.