{"id":1992,"date":"2015-11-23T13:39:27","date_gmt":"2015-11-23T18:39:27","guid":{"rendered":"http:\/\/web.colby.edu\/cogblog\/?p=1992"},"modified":"2015-12-19T17:02:08","modified_gmt":"2015-12-19T22:02:08","slug":"can-sleepiness-affect-your-eyewitness-memory","status":"publish","type":"post","link":"https:\/\/web.colby.edu\/cogblog\/2015\/11\/23\/can-sleepiness-affect-your-eyewitness-memory\/","title":{"rendered":"Can Sleepiness Affect Your Eyewitness Memory?"},"content":{"rendered":"

It\u2019s a given that as college students, we all feel tired from time to time. Well, maybe more than from time to time. Walking across campus, have you ever heard people saying things like \u201cI got two hours of sleep last night,\u201d \u201cI slept terribly last night,\u201d \u201cI\u2019m going to pass out right now,\u201d or something along those lines? I\u2019m sure you have at some point.\u00a0\"sleepiness<\/a><\/p>\n

We have all heard that it\u2019s important to get our sleep. This is partly because there has been a lot of research showing that our episodic memory, or memory for specific details and events, is better after a period of sleep. For example, if you were to go out on the town and attend a show, your memory for the details and events of that show would be better the next day if you got eight hours of sleep, as opposed to staying out in the city all night. One reason for this phenomenon is that a function of sleep is consolidation (Diekelmann & Born, 2010), or the neural process by which memories are strengthened and more permanently stored. The more sleep you get, the more consolidation occurs, and the better your memories become.<\/p>\n

<\/p>\n

There has been a lot of research regarding the effects of sleep on episodic memory, but most of this research has investigated the effects of sleep when encoding, the process of inputting information into memory, occurs before we sleep. That is, researchers have investigated how differences in sleep affect the\u00a0recollection of episodic memories if the participant encodes the information, sleeps, and is then tested. It is now pretty generally accepted that sleeping between the encoding and testing of information will help you better retrieve that information from long-term memory (McBride and Cutting, 2016), which is our long-term storage of information\u00a0after it\u00a0has been processed.<\/p>\n

But what are the effects of sleep on our episodic memory when the encoding occurs after sleep? Going back to the example of the show, if you were really tired while\u00a0attending the show, would your episodic memory be worse than if you were well rested and wide awake? On the way home, would you have more trouble remembering the color of the characters\u2019 costumes\u00a0than if you were well rested? \u00a0There is much less research regarding the effects of sleep on episodic memory when the sleep occurs prior to\u00a0encoding.<\/p>\n

\"clown\"<\/a>

The Bank Robber<\/p><\/div>\n

In a recent study entitled \u201cThe Effects of Recent Sleep Duration, Sleep Quality, and Current Sleepiness on Eyewitness Memory\u201d (2013), Dr. Craig Thorley of the University of Liverpool\u2019s School of Psychology set out to investigate this very question. He investigated specifically the effects of participants\u2019 current sleepiness, the duration of their previous night’s sleep, and the quality of that sleep on their eyewitness memory (a form of episodic memory). He did so by examining how these three sleep-related variables affected both the recollected\u00a0amount (quantity) and accuracy\u00a0of specific central and peripheral details of a crime scene video. In this study, central details were those that were in the center or foreground of the video and peripheral details were those that were in the background. It is important to note that Thorley did not instruct certain participants to sleep more or less than others before the study. Therefore, all of the variations in sleep duration, quality, and current sleepiness were natural.<\/p>\n

The procedure involved the participants first rating their current sleepiness levels using the Stanford Sleepiness Scale (see below). After finishing the questionnaire, participants watched a short video of a bank robbery. The video, which was a clip from the movie \u201cThe Stick-Up,\u201d is a classic bank robbery, executed to perfection. To watch the video, click here<\/a>. After the video, participants completed the St. Mary\u2019s Hospital Sleep Questionnaire, which assessed the duration and quality of the\u00a0participants’\u00a0previous night\u2019s sleep. Then, the participants\u2019 eyewitness memory \u00a0was tested using a 16-question memory test.<\/p>\n

\"Stanford<\/a>

The Stanford Sleepiness Scale<\/p><\/div>\n

Eight questions related to central details, such as \u201cdid the robber wear beige overalls?\u201d (Thorley, 2013) and eight related to peripheral, or background details of the video. Participants answered either \u201cyes,\u201d \u201cno,\u201d or \u201cI don\u2019t know\u201d to the 16 questions. By answering, \u201cI don\u2019t know\u201d the participant opted out of that question. Using the results of the test, Thorley measured both the recollection quantity and accuracy of the participants\u2019 eyewitness memory for central and peripheral details. Recollection quantity, or the proportion of information correctly remembered, was measured by dividing the number of correct answers out of 16. Recollection accuracy is a bit different. Recall that participants were allowed to answer, \u201cI don\u2019t know,\u201d thus opting out of the question. Recollection accuracy is the proportion of answered questions<\/em> that are correct. So, recollection accuracy was calculated by dividing the number of correct answers by the number of questions that were answered with \u201cyes\u201d or \u201cno\u201d (not opted out of). For example, if a participant answered only 10 questions with \u201cyes\u201d or \u201cno\u201d and got 8 correct, his or her accuracy would be 80%.<\/p>\n

Contrary to what you may have thought, Thorley found that when tested only a few minutes after witnessing the crime,\u00a0sleep duration, sleep quality,\u00a0and\u00a0current sleepiness (all prior to encoding) seem to have a fairly minor effect on overall episodic, eyewitness memory. In terms of the central, foreground details of the crime, he found that neither previous sleep duration, sleep quality, nor current sleepiness seemed to have an effect on how many central details were recalled (quantity) or how accurate those recollections were (accuracy). In terms of peripheral details, he found that none of the sleep-related variables seemed to affect how many peripheral details (quantity) participants could remember. However, Thorley did find that participants\u2019 current sleepiness levels and the quality of their previous night’s sleep seemed to affect how accurate their recollection of peripheral details was. The lower the quality of the participants\u2019 previous night\u2019s sleep and the higher their current sleepiness levels were, the lower their peripheral detail recollection accuracy was.<\/p>\n

Well, I guess that\u2019s good right? \u00a0It seems that if you\u2019ve slept very little, very poorly, or feel very tired prior to encoding the details of a crime, it\u00a0won\u2019t have an effect on how well you can remember the central details of what happened. However, what about if you were asked to testify a week later? Would these pre-encoding sleep factors\u00a0seem to affect the your recollection of crime details then? Thorley\u2019s study tested the participants\u2019 episodic memory of the crime scene extremely soon after they encoded the information. It would be interesting to see if the participants\u2019 recollection quantity and accuracy of the crime details would change if the testing was delayed.\u00a0\"interview\"<\/a><\/p>\n

Also, eyewitness testimonies need to be taken very cautiously. When it comes to these testimonies, the slightest of inaccuracies can cause an innocent person a lot of harm or let\u00a0a criminal get off free. For example, keeping with the video that Thorley used in his study, let’s say there was an accomplice of the clown that was sneakily helping with the robbery. This would have been a peripheral detail of the crime scene and according to Thorley\u2019s results, could have been inaccurately recollected if the witness called to testify was very sleepy during the incident. This seemingly small inaccuracy could lead to that accomplice walking the streets. The point is, although the results from Thorley\u2019s study show that sleep quality and current sleepiness seem to only have an effect on peripheral detail recollection accuracy, it is still very important to look at whether or not an eyewitness has had poor sleep quality or is sleepy at the time of the crime. He or she could have errors in his or her recollection of the peripheral, yet still very important details.<\/p>\n

\u00a0There is still relatively little research regarding the effects of sleep of episodic memory when differences in sleep occur before the encoding of information. Therefore, more research needs to be done in this realm of memory research. However, Thorley\u2019s findings suggest that if you do witness a crime when you are tired, or slept poorly the night before, and are asked to recall what happened soon after, you should warn the investigator that the accuracy of the peripheral details you report may not be very accurate. But your recollection of the central details should be pretty good!<\/p>\n

To read the entire study by Dr. Craig Thorley, click here<\/a>.<\/p>\n

To read a related blog post\u00a0regarding executive functioning\u00a0and sleep, click here<\/a>!<\/p>\n

To read a blog post regarding sleep deprivation and\u00a0false memory, click here<\/a>!<\/p>\n

To read blog more CogBlog posts on memory in general, click here<\/a>!<\/p>\n

 <\/p>\n

References:<\/p>\n

Thorley, C. (2013). The Effects of Recent Sleep Duration, Sleep Quality, and Current Sleepiness on Eyewitness Memory.\u00a0Applied Cognitive Psychology,<\/i>\u00a027<\/i>, 690-695.<\/p>\n

McBride, D., & Cutting, J. (2016).\u00a0Cognitive Psychology: Theory, Process, and Methodology<\/i>. Sage.<\/p>\n

 <\/p>\n

Images (in the order they appear):<\/p>\n

Image #1 was retrieved from here<\/a>.<\/p>\n

Image #2 was retrieved from here<\/a>.<\/p>\n

Image #3 was retrieved from here<\/a>.<\/p>\n

Image #4 was retrieved from here<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

It\u2019s a given that as college students, we all feel tired from time to time. Well, maybe more than from time to time. Walking across campus, have you ever heard people saying things like \u201cI got two hours of sleep last night,\u201d \u201cI slept terribly last night,\u201d \u201cI\u2019m going to pass out right now,\u201d or […]<\/p>\n","protected":false},"author":7330,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[80215],"tags":[129785,130349,542],"_links":{"self":[{"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/posts\/1992"}],"collection":[{"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/users\/7330"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/comments?post=1992"}],"version-history":[{"count":18,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/posts\/1992\/revisions"}],"predecessor-version":[{"id":2361,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/posts\/1992\/revisions\/2361"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/media?parent=1992"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/categories?post=1992"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/cogblog\/wp-json\/wp\/v2\/tags?post=1992"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}