Overhead Side Figure 1: 15 Point Walker 1) Point light walker consisting of 15 points. 2)Actual stimuli: Same walker embedded in noise. 3) Same walker in noise with lines connecting joint. Figure 2: 9 Point Walker 1) Point light walker consisting of 9 points. 2) Actual Stimuli: Same walker embedded in noise. 3) Same walker in noise with lines connecting joints and showing where missing points are in space. Results • Noise tolerance thresholds increased at about the same rate for both groups (see Figure 3). • However, tolerance thresholds are lower for the ASC group than for the control group. • At low numbers of signals points they appeared almost completely unable to detect the biological motion signals. References Blake, R., Turner, L. M., Smoski, M. J., Pozdol, S. L. & Wendy L. Stone. (2003). Visual Recognition of Biological Motion is Impaired in Children with Autism. Psychological Science, 14(2), 151-157. Dakin, S. & Frith, U. (2005) Vagaries in Visual Perception in Autism. Neuron, 48, 497-507. Moore, D.G., Hobson, R.P., & Lee, A. (1997). Components of person perception: An investigation with autistic, non-autistic retarded and typically developing children and adolescents. British Journal of Developmental Psychology, 15, 401–423. Neri, P., Concetta Morrone M. & Burr, D. C. (1998) Seeing Biological Motion. Nature 395(Oct), 894-896. Action Understanding in Autistic Spectrum Conditions: Social and Perceptual Factors Lawrie McKay1, Phil McAleer1, Jennifer Mackie1, Judith Piggott2,David R Simmons1, Frank E Pollick11Department of Psychology, University of Glasgow2Cardiff University Experiment 4: Judgement of Intention from Video and Animacy Displays Background • It has previously been observed that people with Autistic Spectrum Conditions (ASCs) have difficulty processing biological motion and/or complex motion relative to control participants. (Blake et. al. 2003, Moore et. al 1997). • Is this difficulty due to the perceptual problem of integrating motion information across space and time, or the cognitive problem of interpreting the meaning of a veridically perceived motion stimulus? • We devised a battery of tests which required different degrees of perceptual and social processing. • Our ASC group consisted of 4 adult males between the ages of 18 and 25 with Autistic Spectrum Diagnoses according to the Autistic Diagnosis Interview (ADI). Our control group consisted of five neurotypical adult males between the ages of 18 and 25. • Actors were filmed performing six intentions on a 10ft square stage using two digital video cameras: one positioned directly above centre stage (Overhead); the second positioned inline with the centre of the side of the stage (SideView). • The X and Y co-ordinates were extracted from the footage using the EyesWeb open platform for multimedia production and motion analysis, (www.eyesweb.org). • These co-ordinates were filtered to reduce noise and used to create QuickTime movies depicting white disk(s) on a grey background Experiment 2: Discrimination of Instrumental Actions from Action Blends • Experiment 2 set out to examine the ASC group’s sensitivity in action recognition. • Participants were shown PLDs comprising action blends created from two actions, a knock and a lift. • The task was to decide which of the two actions was being performed in the display Experiment 1: Detection of Biological Motion in Noise • 6 Intentions: CHASE, FIGHT, PLAY, FLIRT, GUARD & FOLLOW • 2 Viewpoints: OVERHEAD (o) & SIDE (s) • 2 Display conditions: ANIMACY & VIDEO • Paradigm similar to that used by Neri et. al. (1998) to determine noise tolerance thresholds for detection of biological motion in noise. • Signal points were taken from point light displays (PLDs) generated from human walkers and noise masks consisted of a varying number of scrambled signal points. • The number of walker signal points varied between 3 and 15(See Figures 1 & 2). As can be seen from Figure 4, there was similar sensitivity (slope) to the stimuli for both groups, though the ASC group has a slight bias towards reporting “knock”. Experiment 3: Discrimination of Affect from Biological Motion Displays The ASC Group were poorer at judging the intentions of people in Video Displays, compared to controls. • Our third experiment set out to test whether people with ASCs were able to use social information in a similar manner to instrumental information in discriminating between throwing actions performed with different affects. • Participants were asked to determine whether throwing actions were angry, happy, neutral or sad. Preliminary Conclusions • On both tasks involving social judgements (Exps 3 & 4), the ASC group performed more poorly than controls. • However, the ASC group also showed deficits in processing biological motion in noise (Exp 1), particularly at low numbers of signal points. • One possible explanation for the deficit in motion processing is increased internal noise in the visual systems of the ASC group (Dakin & Frith, 2005). As can be seen in Figure 5, the proportions correct for the ASC group are smaller than for the control group, suggesting a difficulty with identifying the affect the actions from movements Acknowledgements We would like to acknowledge the Wellcome Trust for their support of Jennifer Mackie in her vacation scholarship.