POSTDICTION VARIABLES
Postdiction variables are variables that are measurable products that correlate with the accuracy of eyewitnesses in a noncausal manner (Wells, Memon, & Penrod, 2006). These measurable products include confidence, response latency, and the self-reported decision process (Wells et al., 2006).
Confidence
An eyewitness’s confidence in their identification is a heavily researched question in the study of eyewitnesses. The connection between confidence and accuracy has been heavily debated. Courts have endorsed the idea of reliability of an eyewitness being a reflection of their level of confidence (Wells et al., 2006). Jurors rely on the confidence of the eyewitness when judging whether or not their decision was accurate even in the absence of instructions to pay attention to eyewitness confidence (Wells et al., 2006).
Eyewitnesses’ researchers focused on the relationship between eyewitnesses-identification confidence and eyewitness-identification accuracy. However, the relationship between confidence and accuracy varies greatly. The level of memory strength can affect the confidence-accuracy relationship (Wells et al., 2006). When memory strength is stronger the relationship between confidence and accuracy is higher verses when the memory strength is weaker (Wells et al., 2006). The relationship also depends on how similar the mistakenly identified person is to the actual target; and when it is calculated across witnesses under different viewing conditions rather than among witnesses who had the same viewing conditions (Wells et al., 2006). Research has not supported the notion that confidence is a highly reliable indicator of accuracy and high error rates appear amongst even the most confident witnesses (Wells et al., 2006).
Response Latency
Response latency is the amount of time the eyewitness takes to make an identification. Research has indicated through a considerable amount of data that witnesses who make accurate identifications from lineups tend to do so faster than those witnesses who make inaccurate identifications (Wells et al., 2006). This is because the comparisons made to the target involve a large number of common features between memory and stimulus (Wells et al., 2006). This results in a slower decision. Response latency is a performance variable that can be measured without the eyewitness’s awareness (Wells et al., 2006). The response latency of 10-12 seconds worked best in four different data sets (Wells et al., 2006). The response latency had a probably of 90% accuracy when witnesses answered in under 10-12 seconds but only 50% accuracy when going over the 10-12 seconds (Wells et al., 2006). However, in more recent research, it has been found that the 10-12 second rule is not stable across variations in witnessing and lineup conditions (Wells et al., 2006). This information made the 10-12 second rule unstable but because accurate identifications are made faster than inaccurate identifications has made this finding more reliable (Wells et al., 2006).
Self-Reported Decision Processes
Self-reported decision processes is the report of the processes that the eyewitness uses to make their identification decision (Wells et al., 2006). The problem with self-report decision processes is that they are subject to distortion. Also, if eyewitnesses had any indication that these self-reports would be utilized to assess accuracy of their identifications, they could shape their answers accordingly (Wells et al., 2006).
Reference
Wells, G. L., Memon, A., & Penrod, S. (2006). Eyewitness evidence: Improving its probative value. Psychological Science in the Public Interest, 7(2), 45-75.
Confidence
An eyewitness’s confidence in their identification is a heavily researched question in the study of eyewitnesses. The connection between confidence and accuracy has been heavily debated. Courts have endorsed the idea of reliability of an eyewitness being a reflection of their level of confidence (Wells et al., 2006). Jurors rely on the confidence of the eyewitness when judging whether or not their decision was accurate even in the absence of instructions to pay attention to eyewitness confidence (Wells et al., 2006).
Eyewitnesses’ researchers focused on the relationship between eyewitnesses-identification confidence and eyewitness-identification accuracy. However, the relationship between confidence and accuracy varies greatly. The level of memory strength can affect the confidence-accuracy relationship (Wells et al., 2006). When memory strength is stronger the relationship between confidence and accuracy is higher verses when the memory strength is weaker (Wells et al., 2006). The relationship also depends on how similar the mistakenly identified person is to the actual target; and when it is calculated across witnesses under different viewing conditions rather than among witnesses who had the same viewing conditions (Wells et al., 2006). Research has not supported the notion that confidence is a highly reliable indicator of accuracy and high error rates appear amongst even the most confident witnesses (Wells et al., 2006).
Response Latency
Response latency is the amount of time the eyewitness takes to make an identification. Research has indicated through a considerable amount of data that witnesses who make accurate identifications from lineups tend to do so faster than those witnesses who make inaccurate identifications (Wells et al., 2006). This is because the comparisons made to the target involve a large number of common features between memory and stimulus (Wells et al., 2006). This results in a slower decision. Response latency is a performance variable that can be measured without the eyewitness’s awareness (Wells et al., 2006). The response latency of 10-12 seconds worked best in four different data sets (Wells et al., 2006). The response latency had a probably of 90% accuracy when witnesses answered in under 10-12 seconds but only 50% accuracy when going over the 10-12 seconds (Wells et al., 2006). However, in more recent research, it has been found that the 10-12 second rule is not stable across variations in witnessing and lineup conditions (Wells et al., 2006). This information made the 10-12 second rule unstable but because accurate identifications are made faster than inaccurate identifications has made this finding more reliable (Wells et al., 2006).
Self-Reported Decision Processes
Self-reported decision processes is the report of the processes that the eyewitness uses to make their identification decision (Wells et al., 2006). The problem with self-report decision processes is that they are subject to distortion. Also, if eyewitnesses had any indication that these self-reports would be utilized to assess accuracy of their identifications, they could shape their answers accordingly (Wells et al., 2006).
Reference
Wells, G. L., Memon, A., & Penrod, S. (2006). Eyewitness evidence: Improving its probative value. Psychological Science in the Public Interest, 7(2), 45-75.