Survey questions often ask respondents for autobiographical information.  The accuracy of responses to these questions is dependent on the respondent’s ability to recall memories.  Unless you have a condition known as hyperthymestic syndrome you do not have a superior autobiographical memory.  Neither do your survey respondents.  In fact there have only been three confirmed cases of individuals with hyperthymestic syndrome,  a name given by researchers at University of California-Irvine who used the greek for excessive (hyper) and remembering (thymesis).  One of the subjects researched went by the initials AJ until she used her real name, Jill Price, in a book published last May titled “The Woman Who Can’t Forget: The Extraordinary Story of Living with the Most Remarkable Memory Known to Science – A Memoir.”  She was originally the subject of a study published in the Journal Neurocase in 2006 that led to the discovery of two other cases: a Wisconsin man named Brad Williams and Rick Barron from Ohio.  What makes them extraordinary is their ability to recall specific events from their personal experience and the abnormal amount of time they spend thinking about it.  When you ask them about a random date they can describe events that occurred on that day,  tell you what the weather was like, and other trivial details that most people would not be able to recall.   For most people the greater the demand a question places on memory, such as being asked to recall trivial details occurring on any given random date, the less accurate the responses and therefore the less reliable the survey data that is collected.  Because recall is not reliable, respondents rely on inferences to fill in the blanks for any details that they are not able to recall.  Understanding the cognitive processes involved with memory in survey response can help you improve the reliability of your surveys.

In order to appreciate how remarkable an accurate memory is then we must first understand what goes into forming and retrieving a memory.  Memory is usually understood in general terms as an individual’s mental ability to store, retain, and recall information.  Memories are stored in nerve network patterns.  Each nerve cell in the brain connects with a thousand other nerve cells.  Memories are retained on the basis of whether these connections are strong or weak. When we learn to do something better such as play a musical instrument then these connections become stronger.  Information that comes from a respondent becomes more reliable when a respondent is exposed to the same information repeatedly.  When we learn to ignore something such as a the constant humming coming from a train near an apartment then these connections become weaker. Likewise the information that a survey respondent is likely to remember is not going to come from experiences they have consciously sought to ignore.  A nerve cell is also referred to as a neuron.  Memories are recalled when we activate a network of interconnected neurons.  Information comes to us through our sense of sight, smell, taste, hearing, and touch.  When we recall a memory we re-fire the same neural paths that we used to sense the original experience and in a way we recreate the event.  A question may ask about an event that was experienced by a respondent but it could also ask about a concept or an idea.  When memories come from concepts or ideas we extract the essence of sensed experience to form generalized concepts.  This means that actual events and the how they are perceived by the respondent’s senses have a physical basis even when questions are only relevant to a particular concept or idea.
In the movie “50 First Dates” Adam Sandler must win Drew Barrymore’s heart each day as if it were the first time they met because she suffers from memory loss as the result of a brain injury.  She is no longer able to encode, store, and retrieve new memories.  Every morning when she wakes up with no recollection of the previous day.  She is able to recall previously stored memories from before she suffered an injury but she is no longer able to create new memories based on recent events.  Short term memory allows you to remember recent events, experiences, and information while long term memory stores information so that it can be used again and again.  In order for Drew Barrymore to create new memories she must store information in a usable form in a process known as encoding.  Memory must then be stored for later use.  Much of these stored memories lie outside of our awareness until we need it. She must then be able bring the stored memories into conscious awareness.  No matter how hard Adam Sandler tried he could not get Drew Barrymore to remember him the next day because the brain injury she suffered did not allow memories to ever develop to the point where they were able to be encoded, stored, so they could be later retrieved.  When a question is asked in a survey it is assumed that any reference to past events are in a place where they can be brought into conscious awareness.  The stage model of memory holds that memory occurs in three stages: sensory memory, short term memory, and long term memory.
During the sensory memory stage we hold onto sensory information for fractions of a second before some of the data is moved over to short term memory. Only the data that catches the respondent’s attention is moved to short term memory.  Data that does not catch their attention is lost for good.  Questions that are not based on issues that are likely to attract a respondent’s attention initially may not have any basis for reference.  Short term memory is also known as working memory.   When a survey question is too long, contains too many embedded clauses or complex syntax, it can impose a cognitive burden on the respondent’s working memory.  Every respondent has a different level of working memory.   Working memory is generally assumed to be around 20-30 seconds.  Many short term memories are forgotten.  This is because short term memory is small. It can hold about 7 items at one time.  However when information is attended to then it can often be brought to the attention of working memory.
Remember when we discussed hyperthymestic syndrome.  One of the criteria established for this was an excessive amount of time thinking about past experiences.  Memories are therefore present in working memory even when they concern seemingly trivial events.  Unless your respondent is unusually obsessed with the question you are asking then this is not always going to be the case.  Particularly when you ask them a question that they may have not thought about for a while.  The accuracy of survey responses decreases over time.  If a question is relevant to a respondent then it will be easier for them to retrieve this information into working memory.  Therefore the questions that you ask your respondent are likely to increase in accuracy in relation to relevancy.  When memory passes into long term memory it exists on a preconsious or unconscious level.   While this information exists largely outside of our level of awareness it can still be brought into working memory fairly easily.  Long term memories can be used to make decisions, interact with others, and solve problems.  The processes involved with long term memory are the same processes that Drew Barrymore could no longer accomplish in “50 First Dates.”   The three processes involved are encoding, storing, and retrieval.
Finally, memories are arranged in clusters in which related information is grouped together so that it can then be parsed more easily.  When information is organized into categories it becomes easier to remember and therefore recall into working memory.  You might associate a coffee shop with hours spent studying, reading, and the intelligent or funny conversations you had while you were there. Over time similar events you experienced while at that coffee shop begin to get grouped together.   As time passes you are no longer able to separate what you think you experienced at the coffee shop from what you infer happened.  If someone asked you what you did at a coffee shop you have not been at for awhile then all your memories will blend in with other memories.  It might seem like you were either reading something or talking with someone you usually went there with.  However, certain events while you were at the coffee shop may trigger memories that distinguish one experience from another.  The time you spilled coffee on your laptop for example.  Including cues in survey questions can allow respondents to distinguish one event from another and improve the accuracy of their survey responses.  Another way to improve memory in surveys is by asking questions that surround a target event in order to bring your respondent back to the event’s original memory encoding. For example, you may be able to recall what you were doing at the coffee shop better if you are reminded that you slept through an exam the next day.  Understanding how memory is used to recall events can improve the accuracy of your survey by separating events to the extent that you are able to distinguish them.