International Meeting for Autism Research: Response Variability in a Low-Functioning Individual with Autism: Practical and Theoretical Implications

Response Variability in a Low-Functioning Individual with Autism: Practical and Theoretical Implications

Thursday, May 20, 2010
Franklin Hall B Level 4 (Philadelphia Marriott Downtown)
1:00 PM
E. J. Pickett , Cognitive Neurology/Neuropsychology, Dept. of Neurology, Johns Hopkins Medical Institutions, Baltimore, MD
N. M. Billings , Cognitive Neurology/Neuropsychology, Dept. of Neurology, Johns Hopkins Medical Institutions, Baltimore, MD
L. V. Van Droof , Cognitive Neurology/Neuropsychology, Dept. of Neurology, Johns Hopkins Medical Institutions, Baltimore, MD
B. Gordon , Cognitive Neurology/Neuropsychology, Dept. of Neurology, Johns Hopkins Medical Institutions, Baltimore, MD
Background: In addition to difficulty with initial learning, it is also widely recognized that low-functioning individuals with autism exhibit considerable variability in demonstrating what they presumably have learned. Such variability has many practical consequences, such as the difficulty obtaining valid assessments. But it also may have a more profound theoretical significance, because it may arise, in whole or in part, from an intrinsic weakness and/or variability in the underlying neural representations of knowledge in such individuals.
Objectives: To establish the magnitude of response variability for well-known stimuli, in a simple response paradigm, in familiar and unchanging circumstances, in one extensively studied low-functioning individual autism. We reasoned that variability found under these circumstances would have a greater chance of being due to intrinsic variability, rather than extraneous factors.
Methods: DL (not his real initials) is a nonverbal, low-functioning male with autism, 18 years old at the time of testing. Stimuli were selected that were purportedly well known to DL, based upon parental report and experimental observation. DL, prior to the study described here, had been tested in his home over a period of 6.5 months by the same team of investigators using similar methods. The two experiments reported here used a two-alternative forced-choice picture-to-picture matching task. In each trial, DL was asked to choose one of two color photographs presented on a computer screen that matched a hard-copy stimulus photo that the experimenter held above the screen. Four conditions were presented to compare DL’s performance with the 24 known items to his performance with unfamiliar items. Condition 1: both the target and distracter photos were Known items. Condition 2: targets and distracters were Unfamiliar. Condition 3: targets were Unfamiliar, distracters were Known. Condition 4: targets were Known, distracters were Unfamiliar. Each condition was presented in ten blocks over five sessions in consecutive order, with Experiment 1 completed prior to Experiment 2. The experiments were identical with feedback for accurate responses only in Experiment 2. All sessions were videotaped.
Results: In Experiment 1, DL achieved 100% accuracy on 30% of the blocks. However, performance varied between 44% and 100%, averaging 96% in Condition 1, 92% in Condition 2, 95% in Condition 3, and 60% in Condition 4. Performance decreased in Experiment 2 despite the feedback. Accuracy ranged from 27% to 94%, averaging 70% in Condition 1, 67% in Condition 2, 56% in Condition 3, and 46% in Condition 4.
Conclusions: Although DL demonstrated competency with the matching task, his performance was quite variable even with highly familiar stimuli on a simple, familiar task, in familiar circumstances. Our data do not yet let us determine the cause of this pronounced variability.  Fluctuating motivation and attention are the obvious possible culprits, but not necessarily evident from the videotaped record. Evaluations of such individuals may have to be sensitive to the possibility that the neural processes required for such tasks may be functioning with much less signal strength, and/or with much greater intrinsic noise, than may be the case in other subject populations.
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