Spreading Activation Model

 The Spreading Activation Model

Collins and Loftus (1975) developed the spreading activation model of semantic memory as a more complex answer to the HNM/TLC's criticisms. It suggests that concepts and nodes are linked together with different levels of conductivity. The more often the two concepts are linked, the greater conductivity.

Collins and Loftus assumed that semantic memory is organised on the basis of semantic relatedness or semantic distance. Nodes that get consistently activated together form stronger connections that make it easier to excite each other, when you look at the network they show this by having shorter links between nodes. The shorter the link, the closer the semantic relation, and so the faster the brain will be at making the connection between the nodes. Furthermore, the longer a concept is accessed, the larger the spread of activation.

Spreading activation is the idea that when a concept is accessed activation spreads out from that node in all directions, as the node attempts to excite all the nodes around it. The higher the conductivity the faster it spreads down that link. Whenever a person thinks, hears or sees, a concept the appropriate node is activated.

The model uses the analogy of neurons: nodes have an activation threshold, and it must be beat for it to fire.

The law of weak cognitive economy is basically a revised version of Collins and Quillian's cognitive economy principle. Information is allowed to be stored at a lower node in the pecking order if the link has been explicit, even if already stored at a higher level. If relations are not stored expressly it is still possible to infer them using hierarchical information.

Collins and Loftus claim that there are different types of links including: -Class membership (a cat is a mammal), -Subordinate (a cat has fur), -Prediction (game-play-people) -Exclusion (a whale is not a fish).

The more attribute to the concepts have in common, the greater number of links between them; e.g. more typical birds will be heavily linked. Semantic relatedness defined as aggregate of the criteralities of the links between them.

Collins and Loftus suggest that relation made are not necessarily logical, rather based on personal experience.