Dual coding is a theory of cognition introduced by Allan Paivio in late 1960s. This theory suggests that there are two distinct subsystems contributing to cognition: one is specialized for language and verbal information, and the other for images and non-verbal information. According to Paivio,
The two mentioned kinds of processing systems, verbal and non-verbal are functionally and structurally independent. This means that each of them can work independently of the other one and that they work on different kinds of representational units. Representational units are “relatively stable long-term information corresponding to perceptually identifiable objects and activities, both verbal and nonverbal.”.3) They are divided into:
For example, a written or spoken word will be processed using the verbal processor and stored as a verbal representation - logogen, but a sound not related to language will be processed by the non-verbal processor and stored as a non-verbal representation - imagen. Logogens and imagens are connected with two kinds of connections:
Both referential and associative types of connections help forming the complex networks of human memory.
Paivio also refers to the issue of problem-solving. Problem-solving is, according to Pavio, the result of joined work of both verbal and non-verbal processing, but if the task is more concrete and non-verbal, the contribution of non-verbal processing system will be more crucial to the outcome and vice-versa.
Dual coding theory suggests that combining verbal and graphical material in learning (or just encouraging students to generate appropriate mental images) should increase the probability that words will activate corresponding images and vice-versa.
This also means that learning material will be easier to relate if it is less abstract.
Paivio also addresses individual differences in tendency and capacity to use imagery:
Common criticisms of dual coding theory suggest that there is no need for two representational systems, since both verbal and non-verbal stimuli are processed in working memory, turned to semantic elements or propositions and are stored in long-term memory. This assumption is sometimes also known as the single-coding theory.5)
Paivio, Allan. Imagery and verbal processes. Holt, Rinehart and Winston. New York, 1971.