Ify a word displayed on a computer screen, observing the word could be verified by eye-tracking data showing that the focus of the individual’s gaze was on the letters that make up the word. Verification of attending to the word, however, requires additional behavior such as reading the word aloud, typing the same word on a keyboard, or something similar. Dube et al. (2010) illustrated the distinction between observing behavior and attending. The test procedure in this study was matching to sample with two-element sample stimuli. The test was presented on a touch-screen computer monitor and the eye tracking research apparatus was ISCAN RK-426PC Pupil/Corneal Reflection Tracking BRDU biological activity System, RK520PC Autocalibration System, and Miniature Head-Mounted Eye Imaging and Line-of-Sight Scene Imaging Systems1. Preliminary testing verified that participants could perform the task with high accuracy (> 90 ) when the sample stimuli were single stimuli (e.g. on a trial with the sample A and comparisons A, B, and C, all participants could reliably select comparison A). These tests verified an understanding of the task, accurate discrimination within the stimulus set to be tested, and adequate motivation. The structure of the test trial is illustrated in Figure 1. Test trials began with two sample stimuli presented in the center of the computer screen (Figure 1, Panel A). The duration of the sample observation period was determined by the participant, who was free to observe the sample(s) for as long as she or he chose. When the participant touched the sample display area with a finger (Panel B), the samples disappeared and three single comparison stimuli were presented immediately in three corners of the screen (Panel C; this procedure is called zero-second delay identity matching). As Figure 1 VelpatasvirMedChemExpress GS-5816 illustrates, the correct comparison matched one of the samples and the other two comparisons matched neither sample; one of the samples had no matching comparison. The sample stimulus in the left or right position appeared in the comparison array on an equal number of trials, and so the participant could not predict which of the samples would subsequently be the correct comparison. Sessions consisted of 36 trials, and different stimuli appeared on all trials, drawn at random from a pool of 180 non-representational forms like those shown in Figure 1.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript1ISCAN Inc., 21 Cabot Rd., Woburn, MA 01801. Augment Altern Commun. Author manuscript; available in PMC 2015 June 01.Dube and WilkinsonPageThe two-sample test was administered to four adults without disabilities and 10 individuals with mild to moderate intellectual disabilities. For all of the adults without disabilities and 4 of the 10 individuals with intellectual disability, high accuracy scores (> 90 ) indicated no overselectivity. They were able to match either of the sample stimuli on almost every trial. The reliably correct matching responses were the behavioral measure that verified observing and attending. Observing was confirmed by the eye tracking data showing visual fixations of both sample stimuli on virtually every trial and mean observing durations ranging from 0.34 to 1.18 s per stimulus per trial. For six of the individuals with intellectual disability, intermediate accuracy scores (53 to 78 ) indicated stimulus overselectivity. The reason that this intermediate accuracy reflects overselectivity follows from the logic outlined pre.Ify a word displayed on a computer screen, observing the word could be verified by eye-tracking data showing that the focus of the individual’s gaze was on the letters that make up the word. Verification of attending to the word, however, requires additional behavior such as reading the word aloud, typing the same word on a keyboard, or something similar. Dube et al. (2010) illustrated the distinction between observing behavior and attending. The test procedure in this study was matching to sample with two-element sample stimuli. The test was presented on a touch-screen computer monitor and the eye tracking research apparatus was ISCAN RK-426PC Pupil/Corneal Reflection Tracking System, RK520PC Autocalibration System, and Miniature Head-Mounted Eye Imaging and Line-of-Sight Scene Imaging Systems1. Preliminary testing verified that participants could perform the task with high accuracy (> 90 ) when the sample stimuli were single stimuli (e.g. on a trial with the sample A and comparisons A, B, and C, all participants could reliably select comparison A). These tests verified an understanding of the task, accurate discrimination within the stimulus set to be tested, and adequate motivation. The structure of the test trial is illustrated in Figure 1. Test trials began with two sample stimuli presented in the center of the computer screen (Figure 1, Panel A). The duration of the sample observation period was determined by the participant, who was free to observe the sample(s) for as long as she or he chose. When the participant touched the sample display area with a finger (Panel B), the samples disappeared and three single comparison stimuli were presented immediately in three corners of the screen (Panel C; this procedure is called zero-second delay identity matching). As Figure 1 illustrates, the correct comparison matched one of the samples and the other two comparisons matched neither sample; one of the samples had no matching comparison. The sample stimulus in the left or right position appeared in the comparison array on an equal number of trials, and so the participant could not predict which of the samples would subsequently be the correct comparison. Sessions consisted of 36 trials, and different stimuli appeared on all trials, drawn at random from a pool of 180 non-representational forms like those shown in Figure 1.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript1ISCAN Inc., 21 Cabot Rd., Woburn, MA 01801. Augment Altern Commun. Author manuscript; available in PMC 2015 June 01.Dube and WilkinsonPageThe two-sample test was administered to four adults without disabilities and 10 individuals with mild to moderate intellectual disabilities. For all of the adults without disabilities and 4 of the 10 individuals with intellectual disability, high accuracy scores (> 90 ) indicated no overselectivity. They were able to match either of the sample stimuli on almost every trial. The reliably correct matching responses were the behavioral measure that verified observing and attending. Observing was confirmed by the eye tracking data showing visual fixations of both sample stimuli on virtually every trial and mean observing durations ranging from 0.34 to 1.18 s per stimulus per trial. For six of the individuals with intellectual disability, intermediate accuracy scores (53 to 78 ) indicated stimulus overselectivity. The reason that this intermediate accuracy reflects overselectivity follows from the logic outlined pre.
