Figure 1
Bayesian models of atypical perception in Autism. A) Bayesian models postulate that in typical learning – new sensory observations (likelihood; red) are integrated with the learned model of the world (Prior; blue), leading to a perception/decision (posterior; orange). B) Hypo-prior model for Autism (Pellicano & Burr, 2012): A weak model of the world (high variance in the prior) increases the reliance on new sensory observations (likelihood) that are relatively more precise than the prior (but as precise in autistic as in typical individuals) C) Precise Likelihood Model (Brock, 2012): Overly precise new sensory observations (likelihood has less variance than in typical individuals, and more precise than the prior) can increase the reliance on new sensory observations.
Figure 2
Coin Task Set up. A) Task design adapted from Vilares et al. (2012): the four conditions of the task – with two types of prior (PN = narrow prior; PW= wide prior) and two types of likelihood (LN= narrow likelihood; LW= wide likelihood) uncertainty. B) The time course of a single trial: participants are asked to estimate the position where a coin fell given where the 5 splashes appeared. C) The trials were organized into 24 short blocks of 12 trials each with participants being told at the beginning of each block which thrower (“A” or “B”) will be throwing the coin (blue bar). Four types of trials are shown – Narrow Prior – Narrow Likelihood (PNLN, black); Narrow Prior – Wide Likelihood (PNLW, grey); Wide Prior – Narrow Likelihood (PWLN, red); and Wide Prior – Wide Likelihood (PWLW, orange).
Figure 3
Likelihood vs. Prior Reliance in the 2-Prior Task. A) Sensory weight (likelihood reliance) for a participant is calculated by obtaining the slope of the regression (orange) between the true centre of the likelihood and participant’s estimates of the coin position for each condition. Slopes closer to 1 (red) indicate that participants are more reliant on likelihood information (mean of the splashes) while slopes closer to zero (green) indicate that the participant didn’t rely much on likelihood information, suggesting that they may have relied on prior information instead. Figure shows an example participant. Each dot corresponds to the response on a given trial. B) Sensory weights per group (Left, NT- orange; right, AS-green) averaged across the four conditions. No group differences were found in likelihood reliance in the Main (2-Prior) Coin Task. C) Average sensory weights per group, separated by condition. The AS group shows reduced context adjustment compared to NT. D) Estimated subjective prior variances, divided per group and condition. No evidence was found for group differences in subjective prior variance. Conditions: PNLN = narrow prior and likelihood; PNLW = narrow prior, wide likelihood; PWLN = wide prior, narrow likelihood; PWLW = wide prior and likelihood.
Table 1
Demographic profiles and scores from self-administered psychometric scales.
| VARIABLE | NEUROTYPICAL (NT) GROUP (N = 25) | AUTISM SPECTRUM (AS) GROUP (N = 25) | TOTAL SAMPLE (N = 80) (48 NT + 25 AS + 7 OTHER) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| M | SD | Range | M | SD | Range | M | SD | Range | |
| Age (years) | 23.96 | 4.82 | 18–35 | 25.48 | 6.501 | 18–35 | 24.69 | 5.16 | 18–35 |
| Sex at Birth (F/M/Intersex) | 15/10/0 | 14/10/1 | 37/42/1 | ||||||
| Gender (F/M/Other*) | 14/10/1 | 13/10/2 | 39/35/5 | ||||||
| Autism Quotient (AQ) | 19.44 | 7.25 | 4–30 | 35.44 | 7.42 | 21–46 | 26.15 | 10.24 | 4–46 |
| AQ Attention to detail | 4.64 | 2.66 | 1–10 | 6.40 | 2.45 | 1–10 | 5.52 | 2.68 | 1–10 |
| AQ Attention switching | 4.68 | 1.93 | 2–9 | 8.52 | 1.66 | 3–10 | 6.60 | 2.63 | 2–10 |
| AQ Social Skill | 3.88 | 2.29 | 0–7 | 7.32 | 2.17 | 3–10 | 5.60 | 2.81 | 0–10 |
| AQ Communication | 3.56 | 2.10 | 0–8 | 8.28 | 1.62 | 4–10 | 5.92 | 3.02 | 0–10 |
| AQ Imagination | 3.08 | 1.97 | 0–8 | 4.92 | 2.41 | 1–9 | 4.00 | 2.37 | 0–9 |
| Sensory Processing Quotient (SPQ) | 117.76 | 14.23 | 90–159 | 106.33 | 27.94 | 58–162 | 108.99 | 23.85 | 50–162 |
| SPQ Vision subscale | 28.96 | 3.82 | 23–38 | 24.44 | 6.96 | 13–44 | 25.94 | 5.99 | 13–44 |
| SPQ Hearing subscale | 28.32 | 4.99 | 19–38 | 26.92 | 5.07 | 19–37 | 27.62 | 5.03 | 19–38 |
| SPQ Smell subscale | 18.88 | 4.19 | 11–28 | 19.64 | 6.73 | 9–34 | 19.26 | 5.56 | 9–34 |
| SPQ Taste subscale | 20.12 | 4.10 | 14–29 | 16.68 | 8.29 | 1–33 | 18.40 | 6.70 | 1 -33 |
| SPQ Touch subscale | 21.48 | 4.56 | 13–29 | 17.36 | 6.70 | 3–32 | 19.42 | 6.03 | 3–32 |
| Beck Anxiety Score | 13.68 | 11.60 | 0–55 | 18.72 | 12.68 | 0–44 | 14.50 | 11.67 | 0 -55 |
| Beck Depression Score | 16.04 | 13.61 | 0–44 | 11.09 | 9.89 | 0–44 | |||
| Antidepressant use(Y/N) | 0/25 | 12/13 | 17/63 | ||||||
| ADHD medication use (Y/N) | 0/25 | 6/19 | 8/72 | ||||||
| Autism Diagnostic Observation Schedule (ADOS) | N/A | 6.64 | 1.78 | 4–10 | 5.87 | 2.26 | 2–10 | ||
[i] Note: * Other Genders include – female to male transgender (1NT & 2 AS).
Figure 4
Performance in the 2-Prior Task. A) Estimation Errors in the 2-Prior Task shows no difference in performance between groups by condition B) Variance of trial-by-trial sensory weights reveal a main effect of Group driven by higher variability in the AS group. (NT: Neurotypical – orange; AS: autism spectrum group -green).
Figure 5
Likelihood Only Task results reveal that the AS group has high variability (i.e., were further from estimating the true centre of the splashes) but show no difference in A) estimation errors compared to the NT group for either Narrow or Wide likelihood variance conditions. B) AS group shows lower sensory weights compared to NT for Narrow and Wide likelihood conditions which may indicate a carryover bias from the main 2-Prior task. (Left, NT- orange; right, AS-green).
Figure 6
Autistic trait behaviour in the Likelihood Only Task. The Likelihood Only Task reveals negative correlations in the Wide Likelihood Condition between autism quotient (AQ) scores and A) subjective likelihood variance and B) Estimation error. An AQ subscale analysis revealed Attention to Detail to be negatively correlated with C) subjective likelihood variance and D) Estimation error.