Quantity and time, time processing in dyscalculia

Cappelletti, M., Freeman, E. D., & Butterworth, B. L.

(2011).Time processing in dyscalculia. Frontiers in psychology, 2.‏

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3243078/

How do we judge the length of time of events (without looking at our watch…)? Of events that last a few seconds? We probably conduct an inner counting of the number of "seconds" the event lasted.  This means that we use numbers to measure time.

This is obvious when we learn to tell time (especially with an analogical watch).  In order to be able to tell time we have to master a few arithmetic concepts ("half past four"; "a quarter to nine"; "a quarter past seven") and to know the "time system" (there are sixty seconds in a minute, sixty minutes in an hour, 24 hours in a day), that in some respects is similar to the base 10 number system.

This interesting study looked into aspects of these phenomena.  Twelve dyscalculic adults and 22 non-dyscalculic adults participated. 

It seems to me, that the assigning of participats to the dyscalculic and non-dyscalculic groups wasn't optimal.  This might have, in my opinion, weakened the results.

How were participants deemed dyscalculic?  They had to satisfy four criteria:

·         A score in the Dyscalculia Screener that is one standard deviation or more below average (more on this test here http://beyondiq.blogspot.co.il/2014/07/dyscalculia-screener-computerized-test.html  ).  They did satisfy this criterion.

·         An average IQ score (at least).  They satisfied this criterion as well.

·         A low score in an arithmetic achievement test (GAD, Graded Difficulty Arithmetic Task).   A look at the data reveals that eight of the twelve dyscalculic participants had a "dull average" score in this test.  A dull average score is not a score that is significantly below average.  The average score of all twelve participants in this test was dull average.

·         Deficient functioning in the arithmetic subtest of the WAIS-R.  A look at the data reveals that out of twelve participants, four scored between 8 and 9 and another had a score of 7.  Since the subtest's average is 10 and the standard deviation is 3, these five participants did not satisfy this criterion.

The authors write that the 22 participants in the control group were not given the dyscalculia screener.  They don't supply the control group's data on the three other criteria.

Under these limitations I will consider the results with caution.  The questions that were asked in this study are interesting in themselves.

The authors first asked the participants questions about everyday situations involving time estimation or knowledge about time:

An example of questions that require time estimation: How much time is needed to make a cup of tea?(they are English…)  How much time is needed to fly from London to New York? (this question is influenced by general information knowledge).

An example of a question that requires exact calculation:  If the time is now 10.35 p.m., what time will it be in 2 h and 50 min?

An example of a question that requires  knowledge about time facts: How many hours are in a day?

An example of a question that requires time comparison:  What time is the latest: 11:45 or 15:30?

There was no difference between the dyscalculics and the control group on questions about time estimation, time comparison and time facts.  Dyscalculics performed significantly worse than controls on questions requiring exact time calculations.

After this phase, the authors looked into the influence of numerical stimuli on the perception of time.  For this purpose the participants performed two tasks.  I'll refer here to one of them:

The participants saw the digit  5 projected on a computer screen for a certain length of time. Then a second digit was projected for a certain length of time.  The second digit could have been 1 or 9.  The participants had to decide whether the second digit was projected for a longer or a shorter period of time than the first digit.

We already know that  children who are not dyscalculic display a numerical stroop effect.  The numerical stroop task involves making a fast decision about the physical size of digits (which digit is physically larger?).  When there is congruence between the digits' value and physical size (5  3) performance of typically developing children is faster than when there is incongruence between the digits' value and physical size (5  3).  This effect does not happen with dyscalculic children.  The reason for that may be that dyscalculic children don't link numbers with their quantitative value.

The numerical stroop effect  indicates  that we link quantitative value with physical size.  Do we likewise link between quantitative value and time perception?

This leads us to the hypothesis that participants in the control group would think that  "1"  is projected for a shorter period of time than "5" was (disregarding the actual situation).  That's because the low value of  1  would affect the subjective perception of time.

We may also hypothesize that participants in the control group would think that "9" is projected for a longer period of time than "5" was (disregarding the actual situation).   That's because the higher value of "9", compared to "5", would affect the subjective perception of time.

We may also hypothesize that this effect will not appear with dyscalculic participants.  They will not perceive the digit 1 as projected for a shorter period of time relative to the digit 5, and will not perceive the digit 9 as projected for a longer period of time than the digit 5.  That's because dyscalculics don't link digits with their quantitative value.  When digits or numbers are not linked with their quantitative value, it's hard to take the next step and link the quantitative value with perceived time length.

The results indeed show that the perception of time of dyscalculic participants was not affected by the quantitative value of numbers.  The perception of time of control subjects was affected by the quantitative value of numbers.  The control group participants perceived the number 9 as projected for a longer period of time than the number 5.  They also perceived the number 1 as projected for a shorter period of time than the number 5, but as projected for a shorter period of time than the number 9.

The meaning of these findings may be that we link between quantitative value and subjective time perception.  People with dyscalculia apparently don’t make such a link.  More research is needed with larger groups and stricter group criteria in order to confirm these findings.