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So as promised in this segment, we'll talk about length of the

recall and reference periods, so estimation

and reconstruction of the past in time.

The length of the reference period is also related to recall era and to

understand this, it's important to look at

some terminology or understand some terminology.

So let me make you work here a little bit.

If you've printed out the slides, you can draw on this

slide to help you remember this and just use your imagination.

So down here we have time and this is today's date.

This is when the survey is done and there is a long field period.

Let's say we have 20,000 people that we interview and it

takes some time for you to be part of that survey.

And you will get asked, so this is, you know,

about the middle of 2014, and you get asked about the

whole 2013 year, which would be this, between the end of

the year and the beginning of the year in this period.

So when I ask you about what happened in

2013, you have to remember, you know, all the

way back to when 2013 ended and all the

way through 2013 in order to answer that question.

So that's the difference when we talk about recall period and reference period.

So the reference period is the time period that's being used

for the estimate later on, that would be the year of 2013

if that matches your research question, whereas the recall period is really

the length of the overall period that you have to remember.

This two can vary and some effect of measurement error actually

do increase quite a bit, if we have a longer recall period.

Some more findings on these recall effects of elapsed time and forgetting.

This is a study done here very early on by Charlie Cannell.

He was a researcher here at the University of Michigan and

with his colleagues he was looking at reporting of hospital visits.

They did a record check study,

so they had the actual true values from the hospital

on hand and could compare the respondent reports to that.

What you see in the first column here

is the weeks between discharge and the interview:

One to ten weeks, 11 to 20, and 21 to

30, it extends on. And then over here, the present not

reported, so there is, you know, an event in the records

and then the proportion that is not reported from those records.

Sorry not proportion but percent, so 3%, 9%, and so on and this

is the n in brackets, the number in the records of these events.

So, you see that the percentage of not reported events of the events in the

records is increasing drastically and by week 51 to 53, about 40% of

all those events are not longer reported by the respondents in this study.

The National Crime Victimization Survey has

played around with different recall intervals.

And David Cantor from Westat and part of our faculty at JPSM,

he did a lot of studies to sort of

fine tune the way victimization can be asked.

And these results here are part of this

whole set of research studies on this topic.

And what you see in these two columns are

the annual victimization rates, estimated with different recall intervals.

So what we see here is rates per 100 persons aged 12 and above.

And in the first column the question asks with the recall interval of

six months and the other one with the recall interval of three months,

so "in the past six months" or "in the past three months."

If there were an issue with the recall intervals, then we should of course see

more events in six months than in three months, which is not the case here, right?

We have pretty high rates for the three months recall interval.

So, you know, auto theft is reported with

2.1 auto thefts per 100 persons aged 12 years

and above in the 3 months recall period

but in the 6 months recall period that's 1.8.

Now it could be, you know, that something happened and it got

more violent, you know, more recently but that is pretty unlikely.

So this has by and large to do

with forgetting and this is a pretty striking result.

Now in general, it is difficult to date events when they happen

because people dont stick or store tags together with

an event, you know, it is hard to remember.

If I were to ask you, "What did you do on March 12th

in 2013?", you might have troubles remembering that. But, you

know, there are of course a few landmark events for which we do know dates.

So if I were to ask you where were you on

September 11, 2001, you might in fact know it or at least if

you were, at that time, were in the United States, you might

quite vividly remember where you have been at that point in time.

Often people have sort of relative landmarks,

so something that is important for themselves.

So, "This was before I entered college" or "before

I got divorced" or "before I got married," you know?

All these elements here can play into the effect and

that helps a little bit in reconstructing this autobiographical sequence.

In general, it's important to know that memory is not a

continuous linear record and people are just able to sort of report them.

Depending on the type of event you might therefore

want to see, "Okay, how might this information be

stored in the respondent's head and what instrument should

I use in my questionnaire to ask for it?

So, do I need a calendar to remind them of what season this was or what not?

Is this a more socially defined period and they need to be asked about these

social events before? Can I ask in the form of elapsed time?"

Or you might want to use idiosyncratic reference points, pointing again

at the technique of event history

calendars to reconstruct the respondent's autobiography.

Now there's another aspect here related to recall

error or in the reporting of past behavior.

And that is, has to do with how you try to report the past.

So do you give estimation or can you actually reconstruct the actual event?

So here the question is, "When do respondents estimate

behavioral frequencies? What estimation strategies are used?" And

so in general, it is true that the more frequent

the behavior is, the more likely estimation will be used.

And again, if you're a smoker or if

you're a frequent coffee drinker, it would be very

difficult for me to ask you, "How many cups of coffee did you drink in the last year?"

Even so, that is the estimate you would want to make from your subsequent research

question point of view. And so instead, you can probably get an estimation,

you know, of "I drink about two cups a day and therefore this would be 365 times two."

Also, the more regular the behavior is, the more likely estimation will be used.

And the more accessible relevant memory is,

the less likely estimation will be used, right?

So if you actually can vividly remember every single time you drank a cup of

coffee, then you don't need that, though

that is less likely for this particular example.

Two more things on estimation.

Rate information is stored in memory for regular behavior.

So as I said, twice a day would be a typical one. But it is also important

to know that an increased number of similar

events decreases the probability of recalling any single one.

And people then rely on something that is

more a generic memory than an episodic memory,

which, you know, if you think it's like "Okay, three times a day

I brush my teeth." It's just there are general routines that you remember

but you don't actually remember, well, all these times

that you went to bed without brushing your teeth.

So it easily can lead to an error

of omission because you might diverge from the regressing.

Remember early in the task, I asked you

about the use of seatbelt and has there been

times when you didn't and that would be another

example for this user schema for reconstructing the past

and that can lead to errors of omission.

And in the next segment, we're going to talk a little bit more about

comprehension problems that can lead to retrieval

issues when we talk about behavioral frequencies.

Memory and Recall: Length of Reference Period

社会调查的问卷设计

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