fifteen children and adolescents with asds ( asperger and high functioning autism ) aged eight to 17 years old were compared with 15 age matched normally developing individuals .
participants with asds were diagnosed by a child and adolescent psychiatrist based on dsm - iv criteria ( 17 ) .
visual memory tasks were assessed in all participants using some tests from cambridge neuropsychological test automated battery ( cantab):paired associates learning ( pal ) : in this test , some boxes are displayed on the screen and opened in a randomized order .
error occurs when the participant selects a box not containing the target stimulus ( 18 , 19).pattern recognition memory ( prm ) : this test has two phases . in the first phase ,
the participant is presented with a series of 12 colored visual patterns for three seconds .
12 paired novel and old patterns are presented in which the participant is required to choose between a pattern they have already seen and a novel pattern ( 20).this test is scored using two indices : a ) mean correct latency ; b ) number correct.spatial recognition memory ( srm ) : this test has also two phases . in the first phase ,
the participant is presented with a white square which appears at five different locations on the screen .
the participant is told to memorize the locations of the square . in the second phase
, the participant sees a series of five pairs of squares , one of which is in a place previously seen in the presentation phase .
this test has two indices for scoring : a ) mean correct latency ; b ) number correct.delayed matching to sample ( dms ) : in this test , one target ( a complex visual pattern ) and four different patterns are presented in four different time intervals .
the four patterns are presented simultaneously or 0 , 4 , and 12 seconds after target presentation .
the participant is instructed to touch the pattern which exactly matches the target ( 21 ) . 
  paired associates learning ( pal ) : in this test , some boxes are displayed on the screen and opened in a randomized order .
error occurs when the participant selects a box not containing the target stimulus ( 18 , 19 ) .
pattern recognition memory ( prm ) : this test has two phases . in the first phase , the participant is presented with a series of 12 colored visual patterns for three seconds .
12 paired novel and old patterns are presented in which the participant is required to choose between a pattern they have already seen and a novel pattern ( 20 ) .
this test is scored using two indices : a ) mean correct latency ; b ) number correct . spatial recognition memory ( srm )
, the participant is presented with a white square which appears at five different locations on the screen .
in the second phase , the participant sees a series of five pairs of squares , one of which is in a place previously seen in the presentation phase .
this test has two indices for scoring : a ) mean correct latency ; b ) number correct . delayed matching to sample ( dms ) : in this test , one target ( a complex visual pattern ) and four different patterns are presented in four different time intervals .
the four patterns are presented simultaneously or 0 , 4 , and 12 seconds after target presentation .
the participant is instructed to touch the pattern which exactly matches the target ( 21 ) .
the test is scored using four indices : a ) mean correct latency ; b ) total corrects ; c ) prob error given correct : this index indicates the probability of error following a correct ; d ) prob error given error : in this index , the probability of error is illustrated following a previous error .
the raven 's progressive matrices ( rpm ) test was administered to evaluate participants ' intellectual abilities ( 22 ) .
asperger syndrome diagnostic scale ( asds ) was used to confirm the asperger 's diagnosis .
this scale is a 50-item , " yes " or " no " questionnaire , designed to identify children and adolescents aged 5 to 18 with asperger syndrome .
these questions cover five different aspects of mental states including cognition , language skills , social interactions , sensorimotor , and maladaptive behaviors ( 23 ) .
the participants were firstly interviewed by a child and adolescent psychiatrist and diagnosed as having autism spectrum disorders based on dsm - iv criteria .
next , they were evaluated using the asds to confirm the diagnosis and were then examined using neuropsychological tests .
independent samples t test was used to compare the two groups in terms of different variables .
iq was considered as covariate and then the two groups were compared again to eliminate the iq effect . in this research
, all statistical analyses were performed using the statistical package for the social sciences ( spss ) , version 14 .
fifteen children and adolescents with asds ( asperger and high functioning autism ) aged eight to 17 years old were compared with 15 age matched normally developing individuals .
participants with asds were diagnosed by a child and adolescent psychiatrist based on dsm - iv criteria ( 17 ) .
visual memory tasks were assessed in all participants using some tests from cambridge neuropsychological test automated battery ( cantab):paired associates learning ( pal ) : in this test , some boxes are displayed on the screen and opened in a randomized order .
error occurs when the participant selects a box not containing the target stimulus ( 18 , 19).pattern recognition memory ( prm ) : this test has two phases . in the first phase ,
the participant is presented with a series of 12 colored visual patterns for three seconds .
12 paired novel and old patterns are presented in which the participant is required to choose between a pattern they have already seen and a novel pattern ( 20).this test is scored using two indices : a ) mean correct latency ; b ) number correct.spatial recognition memory ( srm ) : this test has also two phases . in the first phase , the participant is presented with a white square which appears at five different locations on the screen .
the participant is told to memorize the locations of the square . in the second phase
, the participant sees a series of five pairs of squares , one of which is in a place previously seen in the presentation phase .
this test has two indices for scoring : a ) mean correct latency ; b ) number correct.delayed matching to sample ( dms ) : in this test , one target ( a complex visual pattern ) and four different patterns are presented in four different time intervals .
the four patterns are presented simultaneously or 0 , 4 , and 12 seconds after target presentation .
the participant is instructed to touch the pattern which exactly matches the target ( 21 ) . 
  paired associates learning ( pal ) : in this test , some boxes are displayed on the screen and opened in a randomized order .
error occurs when the participant selects a box not containing the target stimulus ( 18 , 19 ) .
pattern recognition memory ( prm ) : this test has two phases . in the first phase , the participant is presented with a series of 12 colored visual patterns for three seconds .
, 12 paired novel and old patterns are presented in which the participant is required to choose between a pattern they have already seen and a novel pattern ( 20 ) .
this test is scored using two indices : a ) mean correct latency ; b ) number correct . spatial recognition memory ( srm ) : this test has also two phases . in the first phase ,
the participant is presented with a white square which appears at five different locations on the screen .
the participant is told to memorize the locations of the square . in the second phase
, the participant sees a series of five pairs of squares , one of which is in a place previously seen in the presentation phase .
this test has two indices for scoring : a ) mean correct latency ; b ) number correct .
delayed matching to sample ( dms ) : in this test , one target ( a complex visual pattern ) and four different patterns are presented in four different time intervals .
the four patterns are presented simultaneously or 0 , 4 , and 12 seconds after target presentation .
the participant is instructed to touch the pattern which exactly matches the target ( 21 ) .
the test is scored using four indices : a ) mean correct latency ; b ) total corrects ; c ) prob error given correct : this index indicates the probability of error following a correct ; d ) prob error given error : in this index , the probability of error is illustrated following a previous error .
the raven 's progressive matrices ( rpm ) test was administered to evaluate participants ' intellectual abilities ( 22 ) .
asperger syndrome diagnostic scale ( asds ) was used to confirm the asperger 's diagnosis .
this scale is a 50-item , " yes " or " no " questionnaire , designed to identify children and adolescents aged 5 to 18 with asperger syndrome .
these questions cover five different aspects of mental states including cognition , language skills , social interactions , sensorimotor , and maladaptive behaviors ( 23 ) .
the participants were firstly interviewed by a child and adolescent psychiatrist and diagnosed as having autism spectrum disorders based on dsm - iv criteria .
next , they were evaluated using the asds to confirm the diagnosis and were then examined using neuropsychological tests .
independent samples t test was used to compare the two groups in terms of different variables .
iq was considered as covariate and then the two groups were compared again to eliminate the iq effect . in this research
, all statistical analyses were performed using the statistical package for the social sciences ( spss ) , version 14 .
the mean age of children and adolescents with asds was 12.80 ( sd=3.23 ) while the mean age of control group was 10.53 ( sd= 3.04 ) .
with regards to iq , youths with asds had significantly lower iqs compared to normal children and adolescents ( p<0.01 ) ( table 1 ) . 
 
demographic variables in children with asds and normal group in regards to paired associates learning test ( pal ) , individuals with asds had poorer performance on this task compared to normal group ( table 2 )
. there was a significant difference between the two groups on " first trial memory score " ( t = 2.092 , p = 0.046 ) ,  total errors adjusted 
( t = 17.662 , p = 0.015 ) and " total trials adjusted " ( t = 15.794 , p = 0.013 ) . 
  results of visual memory tests in children with asds compared with normal group without considering the iq as the covariance while iq was considered as covariate , none of the pal variables showed any significant difference between the two groups . in terms of pattern recognition memory ( prm ) and spatial recognition memory ( srm ) tests , significant differences were found between the two groups on " number correct " variable in prm ( t = 6.390 , p = 0.045 ) and srm ( t = 1.026 , p = 0.005 ) tests . considering iq as covariate
the differences were eliminated . with regards to delayed matching to sample ( dms ) task , it was found that children with asds had worse performance compared to normal youths on dms task ( table 2 ) .
children and adolescents with asds had less " total corrects " ( t = 0.786 , p = 0.002 ) and more " prob error given correct " ( t = 0.277 , p = 0.012 ) and " prob error given error " ( t = 13.834 , p = 0.019 ) compared to normal group . by eliminating the iq effect , no significant difference was found between the two groups in terms of dms variables .
some studies investigated visual perception and memory in children with autism spectrum disorders ( asds ) , but their findings are not consistent . because these experiments were mostly based on investigating meaningful shapes , the current study was designed to evaluate visual memory using meaningless shapes in children and adolescents with asds .
we found that youths with asds had poorer performance on paired associate learning test which is mediated by temporal lobe compared to normal youths .
it was also found that asds group had poorer performance on recognizing meaningless patterns on prm task , which is sensitive to impairment of temporal lobe .
youths with asds were poorer on visuospatial memory task , which is mediated by frontal lobe ( 24 ) .
they were also poor in matching the patterns to the sample based on the findings of delayed matching to sample task .
this task is sensitive to impairment of frontal lobes and is assumed to be mediated by temporal lobe ( 18 ) .
these findings are inconsistent with the results of some other studies which indicated that children and adolescents with asds have intact object recognition and visual memory ( 25 , 26 ) or showed that youths with asds had a better ability to recognize objects ( 27 ) .
this inconsistency may be due to different tasks that were used in our study as compared to the others .
the visual memory tasks used in previous studies were mostly based on recognizing objects which may have been particularly interesting to children and adolescents with asds , so they could have recognized them easier than otherwise normal developing youths .
therefore , it can be gathered that the findings of this study could show the visual memory ability of children and adolescents with asds with better precision . on the other hand ,
these findings are consistent with the results of ameli 's study on autistic individuals comparing the meaningful and meaningless pictures ( 8) .
they found that individuals with autism have poorer performance on meaningless visual memory patterns whereas they are as good as normal people on meaningful pictures ( 8) .
moreover , when we considered iq as a covariance , the significant difference disappeared and the visual memory ability in both groups proved to be the same . by eliminating the iq effect
, our findings will be consistent with prior study 's results which showed no significant difference between normal youths and asds group .
this means that this ability may be related to global cognitive ability , which is totally lower in youths with asds compared with normal children in the same age group .
in fact , children and adolescents with asds have deficits in different aspects of cognition including the intellectual ability , visual memory , visuospatial recognition , and executive functioning . based on these findings
, we can conclude that youths with asds have poorer performance on meaningless pattern recognition as well as the visuospatial memory compared to normal age matched children and adolescents .
one limitation of this study was the difference between the two groups in terms of their iqs . since the intellectual abilities of youths with asd are mostly lower than their age matched normal group , matching the iqs of the two groups was rather difficult .
the findings of this study suggest that asds children and adolescents are not superior in visual memory ability compared to normal youths .
 objectivevisual memory is an important cognitive ability , which has been studied in individuals with autism spectrum disorders ( asds ) . in such studies 
 meaningful shapes were used more frequently . since meaningless shapes provide a better assessment of short term visual memory , in this study we used them to evaluate visual memory in children and adolescents with asds compared to the normal group.methodsfour visual memory tests of cambridge neuropsychological test automated battery ( cantab ) including paired associates learning ( pal ) , pattern recognition memory ( prm ) , spatial recognition memory ( srm ) and delayed matching to sample ( dms ) were administered to 15 children and adolescents with asds ( high functioning autism and asperger syndrome ) and to 15 normal participants aged 8 to 17,with iq of above 70.resultsindividuals with asds performed worse than the normal group on visual memory tasks . after eliminating iq as a covariate , no significant difference was observed between the two groups in terms of visual memory performance.conclusionit seems that deficits on visual memory tasks in youths with asds could be related to their general intellectual abilities . 