Chapter 7 Chapter Summary

Chapter Overview:

Chapter 7 focuses on generic memory, often known as semantic memory. Generic memories are what we know (not what we remember) and are not tied to specific times or places. Generic memory is comprised of concepts (mental representations of objects, people or events). Four main theories of the organization of generic memory have been proposed: hierarchical-network model, the spreading-activation model, the compound-cue model and the hub-and-spoke model. The first three are based solely on behavioural data and are therefore, not as popular today whereas the hub-and-spoke model is also supported by neurological evidence.

In the hierarchical-network model, concepts are arranged from the most general at the top down to the most specific. The facts associated with the concept are stored at the highest level they apply to. Research using the sentence-verification task supported this model, but some concerns were raised. Notably, the model failed to explain how false statements can be rejected, that the frequency of concept features was a better predictor of verification times than the feature’s level on the hierarchy, the distance traveled on the hierarchy did not always predict verification times, and the typicality effect.

The spreading-activation model, probably the dominant view of generic memory for many years, proposes that concepts are linked together in a network of connected nodes – the more properties concept share, the more links connecting them. When a person thinks of a concept, it is activated in generic memory and that activation spreads outward so that linked concepts are easier to retrieve. This associative priming effect was demonstrated in many, many studies. Despite its popularity, the spreading-activation model has several weaknesses: it is almost impossible to disprove spreading activation, it cannot explain the mediated priming effect, the priming effects can last longer than predicted, and concepts might have multiple representations. Also, concepts are represented as nodes but most research has shown that concepts are represented as patterns of activation not in localized bundles.

The compound-cue model suggests that we will recognize a concept if there is a match between the cues present in short-term memory and the items stored in generic memory. Compounded effects of context cues and multiple associations determine whether the memory is accessed. While this model helps explain some of the findings that where problematic with the spreading-activation model, the lack of neurological support has made this model less popular. 

The fourth model, the hub-and-spoke model, focuses on how generic memory is stored in the brain. As already noted, concepts are not stored as unified nodes but in various feature-based locations that correspond to the sensory and motor areas of the brain. For example, when you access the concept of a cat, the cat’s purr would be stored in the auditory cortex. However, this model proposes that there is also a central hub of integrated concepts stored in the anterior temporal lobe. The hub integrates the concepts while six spokes link the concept to the sensory or motor information about the concept.

Most agree that generic memories begin as episodic memories. Research has shown that it takes about five weeks to transfer from episodic memories into generic memories. Many different brain structures are involved in the creation of generic memories including the hippocampus, the mammillary body, the mammillothalamic tract and the hippocampal gyrus.

Although most agree that concepts are the basic unit of generic memory, some aspects of the neuroscience of concepts are still under debate. While there is some evidence that concepts are amodal, the bulk of it supports the hub-and-spoke model described above with the anterior temporal lobe housing the conceptual hub that integrates the modality-specific attributes of concepts. Even though some neurons only respond to very specific concepts, most evidence suggests that concepts are distributed across many neurons in various areas in the brain. Case studies and computer simulations provide strong evidence that the concepts of living things are processed based on perceptual features and nonliving things based on functionality. This combined with neural-imaging provides significant support for the notion that people learn the features about concepts from perceptual and action-based experiences. There is also some dispute about the stability of concept retrieval with both behavioural and neuroimaging research supporting the notion that different attributes of a concept can be retrieved depending on context. Abstract concepts, which do not relate to objects and actions, are also believed to have modality-specific and/or action-specific representations via their associations to more concrete concepts.

While there is no dispute about how people automatically use categories to help save time and energy, there has been some debate about at what category level we operate at most of the time. Three levels of categories have been proposed: subordinate (e.g., recliner), basic (e.g., chair) and superordinate (e.g., furniture). Early theories suggested that people usually work at the level of basic categories unless they were very familiar with a category. Although not disputed as such, this idea could be expanded to people work at the level that reflects their experiences with these concepts.

Schemas and scripts are also in generic memory. Schemas are cognitive frameworks that help to interpret and organize information. Scripts are a type of schema related to our procedures to events. Research suggests that while concepts rely on the anterior temporal lobe, scripts depend on the prefrontal cortex.

Learning Objectives:

Having read this chapter, you will be able to do the following:

1. Differentiate generic memory from other types of memory.
2. Identify what type of information is stored in generic memory.
3. Describe the hierarchical-network model and identify problems with this model.
4. Describe the spreading-activation model and identify problems with this model.
5. Describe the compound-cue model and explain how it can explain mediated priming.
6. Explain how generic memories are formed.
7. Identify the brain areas associated with generic memory.
8. Discuss evidence that suggests concepts are modality specific, distributed, learned, and flexible.
9. Explain how abstract concepts are coded.
10. Describe the hub-and-spoke model.
11. Differentiate among superordinate, subordinate, and basic category levels.