Virtual Reality Monitoring: How Real is Virtual Reality?
by Keith Hullfish
CHAPTER 2 SOURCE MONITORING THEORETICAL FRAMEWORK
Source monitoring refers to the decision process by which memories are discriminated against each other in order to make attributions about the source of these memories; for example, separating memories for thoughts and imaginations from memories for perceived events. Source refers to a variety of characteristics that, collectively, specify the conditions under which a memory was acquired; for example, the media and modalities through which the source was perceived or the thought processes required to imagine and the characteristics of the mental imagery. Evidence from this source, as originally experienced, is preserved in memory and can later serve as cues to where the memory originated. Monitoring decisions are based on qualities of the retrieved memories, in combination with judgment processes.
2.2 Memory Characteristics
Johnson et al. (1993) defines five basic qualities (also called memory characteristics). These characteristics include: sensory/perceptual information (e.g., sound, color), contextual information (e.g., spatial, temporal), semantic detail, affective information (e.g., emotional reactions), and evidence of cognitive operations (e.g., records of organizing information or generating imagery).
Memories from different sources reflect different qualities. For example, memories of seeing movies in a theater may include greater spatial context due to the wider field-of-view than memories of seeing movies on television. Source identification depends on determining the average differences across these characteristics between sources. These differences help determine the qualities which form the schemas that represent a particular source. Schemas could also be formed by expectations or familiarity with the source. For instance, your schema for your father may include qualities of a deep, dark voice.
2.3 Decision Process
Monitoring decisions are based on discriminating the qualitative differences between the memories, with respect to these characteristics. Source is inferred by matching the qualities of a memory with the activated schemas that represent particular sources. The extent to which the qualities match the criteria set by a particular schema influences the likelihood that the memory is attributed to that source, whether it is the correct source or not. These heuristic-based decisions are common and relatively automatic.
However, source monitoring depends not only on the quality of the information encoded, but also on the quality of the decision process. The sets of criteria available to determine source depend on the choice of schema. Decisions may also be mediated through more controlled, deliberate strategies. These may involve retrieval of supporting memories and extended reasoning. In effect, these decisions incorporate a persons prior knowledge and metamemory assumptions. For example, "a person may remember an extremely vivid dream about a money tree but reason that it could not be an externally generated memory because money does not grow on trees (Johnson & Raye, 1981)." Another example would be attributing an event to imagination because you would not have reacted a certain way if the event really happened.
This controlled decision process offers another set of criteria with which to evaluate the origins of a memory. It "employs a criteria of coherence and plausibility. If a memory is externally-derived, it ought to make sense and conform to our knowledge of the world. Internally-generated memories would then be recognized when they failed to meet this criterion (Cohen, 1991)."
2.4 Conditions Operating Under Source Monitoring
2.4.1 No Explicit Tag
People do not directly retrieve an abstract tag or label that specifies a memory's source. Rather activated memory records are evaluated during remembering (Johnson et al., 1993).
As the average difference between sources in memory increases, the more unique their representations become. Thus, source monitoring tends to highlight characteristics that are unique to a given source. Consequently, memories that are atypical of their class tend to get confused.
2.4.3 Encoding Reduction
Source monitoring relies fundamentally on the quality of information recorded about events initially (Johnson et al., 1993). Anything that prevents a person from fully contextualizing information at acquisition (such as the technological limitations of virtual reality) will reduce encoding of potentially relevant source information.
2.4.4 Weighting and Bias
"Setting criteria includes a number of important aspects: assigning weights to dimensions that might be used in any given decision (e.g., weighting perceptual information more important than affect information); assigning particular confidence to different levels of this weighted information, and assigning particular overt responses (e.g., yes in an old/new recognition task) to specific levels of confidence (Johnson et al., 1993)."
Any criterion that receives an inordinate weight in the decision process and does not specify the actual origin can lead to errors in source monitoring (i.e., confusions). Weighting may be affected in any part of the decision process, but goal-directed activity, metamemory assumptions and biases associated with the controlled processes tend to disrupt source monitoring more frequently.
Predictions depend on the criteria that subjects adopt. The following are examples of the criteria thought to distinguish memories for real and imagined events. Memories of real events are typically rich in cues to their external perceptual origin; colors, perceptual clarity and vividness (sensory properties), and contextual information such as relative spatial location and temporal order (Johnson & Raye, 1981; Johnson, Ray, Foley, & Kim, 1982; Johnson, Foley, Suengas, & Raye, 1988; Johnson, Foley, & Leach, 1988; Suengas & Johnson, 1988). They are also more likely to give rise to supporting memories (Johnson, 1988). There is relatively little evidence of cognitive operations. Consequently, a memory with a great deal of visual and spatial detail and very little cognitive operations may be judged to have been externally derived (i.e., real).
In contrast, a target memory with few perceptual cues, but a lot of cognitive operations is likely to be identified as imagined. The act of creating a mental image of an object or event requires mental effort. Evidence of this effort may be preserved in memory. Internally-generated memories are also more schematic and reflect cognitive operations that produce them (e.g., reasoning, inferring, imagining) (Cohen, 1991). Whereas real events are typically associated with more sensory/perceptual and contextual information, imaginary events are identified with this effort (Johnson, Raye, Foley, & Foley, 1981; Finke, Johnson, & Shyi, 1988; Suengas & Johnson, 1988).
In any case, source monitoring also relies on "the type and amount of these memory characteristics included in the activated memory records (Johnson et al., 1993)." As mentioned previously, these attributions can be either right or wrong. For instance, a very vivid dream (which is atypical of its source) may later be misremembered as actually happening. Source monitoring assumes that confusions between events "arise from the same processes as do accurate classifications of memories; from processes of attribution based on the subjective qualities of experience (Johnson, 1988)." Thus, confusions between a pair of sources in a source monitoring task would indicate that qualities associated with the memory of each source are relatively similar.
Human Interface Technology Laboratory