Object Location Memory

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Sex differences in cognitive abilities have been documented across a variety of tasks including mental rotation in favor of males (Halpern, 1992; Linn & Petersen, 1985) and verbal fluency in favor of females (Halpern, 1992; Spreen & Strauss, 1991).  In general, research suggests that males outperform females on tasks involving spatial ability, whereas females outperform males on tasks involving verbal ability (Collaer & Hines, 1995).  However, Silverman and Eals (1992) developed a task intended to measure object location memory and reported that females outperformed males on their paper and pencil version of this task.  James and Kimura (1997) also reported that women outperformed males on the original version of this task when the location of pairs was exchanged, but not when the locations of objects were shifted to sites previously unoccupied by another object.  Recently, Barnfield (1999) found that their adult data replicated earlier findings, but samples of children at different ages-4 yr., 10-11 yr., and 15-16 yr. did not show sex differences for this task.

Given that this task has generated a great deal of theoretical speculation ranging from the sociobiological (James & Kimura, 1997; Silverman & Eals, 1992) to the hormonal (Barnfield, 1999), we created a computer version of Silverman and Eals (1992) task.  The computer version of this task basically translates the paper and pencil version for testing object location memory into an internet-based experiment that includes multiple object location memory trials which will allow us to examine sex differences for the first and repeated trials of this task.

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The experiment begins with a description of the object location memory task that the participants will be asked to complete and a request for consent.  Participants learn that they will be required to study an array of objects for a designated period of time, the array of objects will then disappear, and the array of objects will reappear but some of the objects will have exchanged position with other objects.  In order to designate whether an object is in an exchanged location, the participant can use the mouse to mark the objects that have moved.  The participant can also unmark an object by clicking on the object again.

The participant is required to complete the practice trials before actually beginning the experiment.  The practice array consists of 10 objects.  Then actual data collection begins with an array of 27 objects.  The participant has 5 trials to solve the object location memory task.

The dependent measures are reported for each of 5 trials so that the full experimental design is a 2 (Gender) x 5 (trials) repeated measures design. 
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Because there are multiple dependent variables, students must first decide which variables are of interest to them.  As noted above, the default analysis provided by the PE_Data_Analysis macro is conducted on the d' measure.  Students can take the outcome of this analysis and perform a series of t-tests to compare the performance of males and females for each of the 5 trials, or they could first conduct an omnibus 2x5 split-plot ANOVA.  The advantage of using the d' measure is that it is a composite measure of performance.  A similar measure that one can compute is the composite measure used by   Silverman and Eals (1992).  This measure, which they call the object location memory score is computed by adding the number of correct hits and correct rejections together and subtracting the number of false hits and misses from this total.

An alternative outcome measure to consider versus Silverman & Eals’ object location memory score, would be the computation of the discrimination index d' (Banks, 1980).  This index is computed using the percentage of false alarms, or false alarm rate, for each trial  and percentage of hits, or hit rate, for each trial (Claremont Graduate University & WISE Project, 2002).  In this study there were 14 exchanged objects, therefore hit rate would be the number correctly identified divided by 14.  There were another 13 unexchanged items in this study, therefore, false alarm rate would be the number of items incorrectly identified as exchanged divided by 13.

In addition to examining composite performance, students might want to compare males and females on the specific performance variables--hits, misses, false alarms, and correct rejections.
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In discussing the results of this experiment, students will want to evaluate whether their results are consistent with previous findings using paper and pencil or computer versions of this task.  Contrary findings could be related to a number of factors including but not limited to the testing environment, presentation and delay times for the object arrays, and response mode, i.e., mouse click on exchanged objects only.

The discussion could also review the various outcome measures to consider for analysis in this study.  For example, is the pattern of findings consistent when examining Silverman and Eals’ object location memory measure versus d’?  In fact, the literature on schema theory has noted that results will vary considering the measurements used for memory (Pezdek, Whetsone, Reynolds, Askari, & Dougherty, 1989).

Finally, the discussion will want to reflect upon the nature of sex differences for this task as well as others reported in the literature.  One important question to consider regarding sex differences for the object location memory task is whether it is a stable and robust finding that warrants theoretical consideration or an unstable and modest finding that suggests multiple factors contribute to this apparent sex difference. 

Banks (1980).  Signal detection theory and human memory.  Psychological Bulletin, 74, 81-99. 

Barnfield, A. M. (1999) Development of sex differences in spatial  memory. Perceptual and Motor Skills, 89, 339-350. 

Claremont Graduate University. (2002, July)..  Retrieved from the WISE project Web site: Signal detection theory: Gaussian model
http://acad.cgu.edu/side/sdt/sdt.html.

Collaer, M.L., & Hines, M. (1995).  Human behavioral sex differences: A role for gonadal hormones during early development, 55-107. 

Halpern, D.F. (1992).  Sex differences in cognitive abilities (2nd ed.).  Hillsdale, NJ: Erlbaum. 

James, T.W., & Kimura, D. (1997).  Sex differences in remembering the locations of objects in an array: Location-shifts versus location-exchanges.  Evolution and Human Behavior, 18, 155-163. 

Linn, M.C., & Petersen, A.C. (1985).  Emergence and characterization of sex differences in spatial abilitiy: A meta-analysis.  Child Development, 56, 1479-1498.

Pezdek, Whetstone, Reynolds, Askari, & Dougherty (1989). Memory for real-world scenes: The role of consistency with schema expectatation. Journal of Experimental Psychology, 15, 587-595. 

Silverman, I., & Eals, M. (1992).  Sex differences in spatial abilities: Evolutionary theory and data.  In J.H.Barkow, L. Cosmides, & J. Tooby (Eds.), The Adapted Mind (pp.533-549). New York: Oxford. 

Spreen, O., & Strauss, E. (1991).  A compendium of neuropsychological tests: Administration, norms, and commentary.  New York: Oxford University Press.

          The author expresses thanks to Leigh-Anne Carter, Margaret Kerns, Rena Walles, and other Saint Anselm students who helped in the development of the use of the object location memory paradigm for Experimental Psychology I courses. Additionally, this program would not be possible without the help and support of the PsychExps team of Ken McGraw, Mark Tew, and John Williams. Please e-mail the author (kflanner@anselm.edu) with any comments you have about the program or other ideas / tips you have for other instructors using this experiment.

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Last revised:November 01, 2003 07:01:31 PM
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