Steyvers & Hemmer (2012): Reconstruction from memory in naturalistic environments

Aim
1. To investigate the interaction between episodic and prior knowledge in naturalistic environments
  1. They wanted to see how prior knowledge was used to reconstruct memory for photographs of normal everyday settings e.g. hotel
Procedure
1. Ppts recruited using a random sample from an experimental ppt pool at the University of California, Irvine
Main Experiment
1. Using the same experimental pool, 49 ppts who didn't do prior testing were selected
2. 10 stimulus pics from prior testing were chosen
  1. 2 from each scene that had elicited the most objects named in the perception test
    1. From these 2 sets of 5 images, 2 from each scene were formed
      1. Ppts only viewed 1 image of each scene to avoid carry-over effects
3. Ppts shown the 5 images for either 2 (prior knowledge) or 10 (episodic) seconds, to control for exposure duration.
  1. 4 possible time trial orderings and ppts were randomly allocated to one
    1. Free recall in their own time
      1. Correct recall of inconsistent objects only come from episodic memory
      2. Recall of objects missing = semantic
  2. 2 seconds = relies on prior knowledge
  3. 10 seconds = relies on episodic memory
Findings
1. The effect of prior knowledge (semantic)
  1. Compared number of objects guessed in expectations test to those actually recalled in 2 experimental conditions (2 and 10 seconds)
    1. Accuracy of object guesses based on the expectation test was over 55% from semantic memory
      1. The actual recall in both experimental conditions was over 80%
        In the 2 second condition, 7 objects were recalled on average
        In the 10 second condition, 9 objects were recalled on average
        Suggests episodic memory played a significant role in recall
2. Incorrect recall of high frequency objects was 9%
  1. Suggests that with naturalistic/ unmanipulated scenes, memory is accurate
    1. In unnatural scenes, the error rate increased to 19%
3. Incorrect recall of low frequency objects was 18%
Conclusions
1. In recall of naturalistic scenes, prior knowledge drawn from semantic memory can contribute to accurate recall in episodic memory tasks, when such scenes are unmanipulated
  1. We draw on general knowledge as good guesses of what is expected to be seen
2. Prior knowledge contributes greatly to the recall of naturalistic environments but not at the expense of accuracy
  1. We're more likely to notice novel items
3. Prior knowledge tends to be unrepresentative of everyday event recall; removing high frequency objects induces false memory - makes memory seem unreliable
4. With naturalistic, unmanipulated context, guesses can be effective due to the high frequency objects present
  1. This frees up cognitive resources to be better spent focusing on novel and unexpected objects in a scene
    1. Recall of consistent and inconsistent objects is benefited using a more ecologically valid approach
Evaluation
1. Weaknesses
  1. culture bias
    1. California
  2. University students used
    1. age bias
  3. Difficult to apply
  4. Despite naturalistic scenes
    1. Artificial lab experiment
      1. Low ecological validity
  5. Demand characteristics
  6. Individual differences
    1. Prior tasks
  7. Ethics
    1. lack of protection from psychological harm
      1. Embarrasment
2. Strengths
  1. No gender bias
  2. Highly controlled, standardised procedure (photos easily resused)
  3. Application: used to help police with eyewitness testimony
  4. Lab experiment - good internal validity
  5. Different time conditions for each ppt removes bias
    1. order effects
  6. Ethics
    1. right to withdraw
    2. consent/ debrief
    3. limited harm
Prior Testing
1. Part 1
  1. 22 ppts required to list objects that they would expect to find in 5 naturalistic scenes (office, kitchen, hotel, urban, dining)
    1. Important to assess prior knowledge and what they would expect to find in naturalistic scenes (control group)
  2. Enter their responses into a computer for at least 1 minute per scene
2. Part 2
  1. A separate group of 25 ppts shown 25 images of the 5 scenes
  2. Asked to name all the objects they could see
    1. A measure of perception
3. Results
  1. Objects were placed into high frequency and low frequency (most and least recalled)
  2. Expectations of high frequency objects tended to be iconic objects e.g.TV in a hotel room

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Steyvers & Hemmer (2012): Reconstruction from memory in naturalistic environments

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