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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
Introduction
The role of Excitation-Inhibition (E-I) balance in sensory processing has been har-nessed through
the use of psychophysical tasks (Edden et al., 2009; Freyberg et al., 2015; Robertson et al., 2013; Snijders
et al., 2013; Trakoshis et al., 2020; Yoon et al., 2010), see (Dickinson, Jones, et al., 2016). An advantage
of psychophysical tasks is that the E-I balance differences inferred from them must be of ‘functional
relevance’. Indeed, one commonly used psycho-physical task for this purpose is the visual-Orientation
Discrimination Task (ODT) (Dickinson, Bruyns-Haylett, et al., 2016; Dickinson et al., 2014; Shaw et al.,
2019), given its well-known association with inhibitory mechanisms (Edden et al., 2009). A vast range of
animal (Katzner et al., 2011; Leventhal et al., 2003; Sillito, 1975; Xia et al., 2013) and human research
(Edden et al., 2009; Kurcyus et al., 2018) supports the vital role of cortical inhibition on orientation
selectivity tuning and perceptual judgment of stimuli’s orientations due to their associations with GABA,
the main inhibitory transmitter. For instance, animal research showed that orientation selectivity tuning
reduced following the application of GABA antagonist (Katzner et al., 2011; Sillito, 1975) but increased
following the application of GABA agonist (Leventhal et al., 2003; Xia et al., 2013). Similarly, enhanced
visual orientation discrimination skills in humans are linked to higher GABA concentration levels in the
visual cortex (Edden et al., 2009; Kurcyus et al., 2018). Together, these ndings suggest that performance
in ODT may provide a useful, al-beit indirect, indicator of cortical E-I balance in the visual cortex.
ODT traditionally uses two different conditions, namely cardinal and oblique conditions. In the
cardinal condition, participants judge orientation deviation from vertical or horizontal reference stimuli
(i.e., 0/90 degrees). In the oblique condition, however, participants judge orientation deviation from
oblique reference stimuli (i.e., 45/135 degrees). It is widely recognised that performance in the cardinal
condition is superior to that in the oblique condition (Dickinson et al., 2015; Dickinson et al., 2014; Edden
Investigation of the Relationship Between Orientation Discrimination
Thresholds, Autistic, and Schizotypal Personality Traits
Abdullah Bin Dawood1* , Abigail Dickinson2 , Myles Jones3
1Department of Psychology, King Saud University, Riyadh, Saudi Arabia, e-mail: Aaldawood1@ksu.edu.sa
2Center for Autism Research and Treatment, University of California, Semel Institute for Neuroscience, Los Angeles, United
States of America, e-mail: abbydickinson317@gmail.com
3Department of Psychology, University of Shefeld, Shefeld UK, e-mail: m.jones@shefeld.ac.uk
Abstract: Imbalances in cortical excitation and inhibition (E-I) have been implicated in both autism spectrum conditions
(ASC) and schizophrenia spectrum conditions (SSC). However, most studies investigate these clinical conditions independently,
possibly due to the difculty of obtaining comorbid clinical populations. As such, the current study investigated the relationship
between performance in the orientation discrimination task “ODT” as a potential proxy for E-I balance and the autistic (as
assessed by Autism Spectrum Quotient “AQ”) and schizotypal personality traits (as assessed by Schizotypal Personality
Questionnaire-Brief “SPQ-BR”) in the general population. 87 healthy adult volunteers participated in the study. We found that
high autistic personality traits are associated with enhanced performance in the oblique condition of ODT. In contrast, high
schizotypal personality traits are associated with poor performance in the vertical condition of ODT. Such associations support
the suggested disruption of cortical E-I balance in ASC and SSC.
Keywords: Excitation inhibition balance, Orientation Discrimination Task, Autistic personality traits, Schizotypal personality
traits, Visual Perception.
Original scientic paper
Received: March 29, 2023.
Revised: April 26, 2023.
Accepted: May 11, 2023.
UDC:
616.89-008.48:159.923.3.075(410)
616.895.8:159.923.3.075(410)
10.23947/2334-8496-2023-11-3-375-387
© 2023 by the authors. This article is an open access article distributed under the terms and conditions of the
Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
*Corresponding author: Aaldawood1@ksu.edu.sa
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
et al., 2009; Orban et al., 1984; Vogels and Orban, 1985), possibly due to the larger number of cortical
cells tuned to cardinally orientated objects compared to obliquely oriented ones (Hubel and Wiesel, 1968;
Manseld, 1974; Manseld, 1974). This neural orientation selectivity has been proposed to explain the
well-known ‘oblique effect’, which refers to performance deciency in judging obliquely oriented stimuli
compared to cardinally oriented ones (Appelle, 1972).
Several studies have shown ODT performance differences in individuals with autism spectrum
conditions (ASC) and schizophrenia spectrum conditions (SSC) compared to neurotypical (NT)
individuals (Dickinson, Bruyns-Haylett, et al., 2016; Shaw et al., 2019). For instance, compared to NT
individuals, those with ASC have been reported to have enhanced performance in oblique orientation
discrimination (as indicated by lower OD thresholds) (Dickinson, Bruyns-Haylett, et al., 2016). However,
the same enhancement was absent for the vertical condition of ODT, possibly due to the ceiling effect
(Garin, 2014a), as vertical OD thresholds are about one-fth of the oblique OD thresholds (Edden et al.,
2009). Additionally, compared to NT individuals, individuals with SSC have been reported to have poorer
performance in ODT (as indicated by higher OD thresholds) in vertical and oblique ODT conditions (Shaw
et al., 2019). Both enhanced and impaired performance in ODT has been suggested to reect cortical
E-I imbalance (Dickinson, Bruyns-Haylett, et al., 2016; Shaw et al., 2019). However, given the practical
difculty in obtaining both comorbid and non-comorbid samples for the same investigation, most studies
have not investigated E-I balance in ASC and SSC simultaneously (Dickinson, Bruyns-Haylett, et al.,
2016; Shaw et al., 2019). This difculty can initially be overcome by measuring the traits associated with
each condition in the general population (Del Giudice et al., 2010; Del Giudice et al., 2014; Ford et al.,
2018; Hurst et al., 2006).
Indeed, in addition to ODT studies in clinical samples with ASC, studies with subclinical traits of
ASC (as measured by Autism Spectrum Quotient “AQ”) have reported that higher autistic personality traits
in NT individuals are associated with enhanced ODT performance in the oblique condition compared to
those with low autistic personality traits (Dickinson et al., 2015; Dickinson et al., 2014). These ndings have
been suggested to indicate increased cortical inhibition in the visual cortex of individuals with high autistic
personality traits compared to those with low autistic personality traits (Dickinson et al., 2015; Dickinson
et al., 2014). This suggestion has also been supported by neurophysiological measures, as individuals
with higher autistic personality traits have higher peak gamma frequency than individuals with low autistic
personality traits (Dickinson et al., 2015), given that variations in peak gamma frequency have been
associated with levels of GABA concentrations in the visual cortex (Edden et al., 2009). Notwithstanding,
such an association between peak gamma frequency and GABA concentration levels in the visual
cortex was not replicated in a more recent study (Cousijn et al., 2014), possibly as a consequence of
methodological differences related to sample size and the techniques used in measuring GABA (i.e., type
of MRS sequence) (Kujala et al., 2015).
Although previous studies have investigated the relationship between ODT performance and autistic
personality traits (Dickinson et al., 2015; Dickinson et al., 2014), we are unaware of any study that has
assessed ODT performance in relation to schizotypal personality traits. Given the differences between
ASC and SSC clinical groups (i.e., enhanced and impaired, respectively) compared to NT control groups,
we may expect poor ODT performance in individuals with higher schizotypal personality traits. However,
there is a link between autistic and schizotypal personality traits (Dinsdale et al., 2013; Ford et al., 2017;
Ford and Crewther, 2014; Nenadić et al., 2021; Russell-Smith et al., 2011); see (Zhou et al., 2019). Thus,
we may expect a similar enhanced ODT performance of individuals with high autistic personality traits in
those with higher schizotypal personality traits.
The current study aimed to investigate the relationship between performance in ODT and both
autistic and schizotypal personality traits in one sample, helping to disentangle these two possibilities.
Ultimately, investigating the relationship between ODT and both autistic and schizotypal traits may provide
a deeper understanding of the neural mechanisms underlying subclinical autistic and schizotypal traits,
given the suggestion that ASC and SSC are two opposites on the same spectrum (Abu-Akel et al., 2018;
Ford et al., 2017; Nenadić et al., 2021; Russell-Smith et al., 2010).
Materials and Methods
Participants
Eighty seven healthy volunteers from the University of Shefeld with normal or corrected to normal
vision participated in the study. Twenty - eight were rst-year Psychology students and received credits
for participation. The rest (N=59) were recruited from the students and staff-volunteering email list of
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
the University of Shefeld and received a £7 Amazon voucher for participation in the study. Participants
provided (written) informed consent before taking part. The study received full ethical approval from the
Department of Psychology University of Shefeld ethics committee.
Orientation Discrimination Task
We used an orientation discrimination task (ODT) initially developed by (Edden et al., 2009) and
had previously been used to measure orientation discrimination in several studies (Bin Dawood et al.,
2020; Dickinson, Bruyns-Haylett, et al., 2016; Dickinson et al., 2015; Dickinson et al., 2014). The ODT
measures orientation discrimination thresholds using a two-alternative forced-choice adaptive staircase
procedure (Leek, 2001; Treutwein, 1995) and was programmed in MATLAB (The MathWorks Inc., Natick,
MA, 2000) with PsychToolbox (Brainard, 1997).
In each trial of ODT, two circular black and white gratings (diameter 4°; spatial frequency three
cycles/degree; contrast 99 %; mean luminance 83 cd/m2) were sequentially presented for 350 ms with
xation of 500 ms between these two gratings, (Figure 1). The rst presented grating is regarded as the
reference grating, whereas the second presented grating is regarded as the target grating. Based on the
orientation of the reference grating, the ODT comprised vertical and oblique conditions. In the vertical
condition, the reference grating was orientated at 0°. In the oblique condition, however, the reference
grating was orientated at 45°. Each condition has two staircases based on the target grating’s rotation
direction (clockwise, anti-clockwise). The staircases implemented one-up three-down procedures,
converging on 79% accuracy (Leek, 2001). For each staircase, the target grating was initially presented 5
degrees away from the reference grating with an initial step size of 1 degree, decreasing 75% after each
reversal.
Figure 1. Schematic diagram of the orientation discrimination task. This gure is reprinted with
permission from (Dickinson et al., 2014).
Participants were asked to sit comfortably on a chair 57 cm away from the monitor in a dimly lit
room. A black circular aperture covered the monitor to eliminate any external orientation cues provided by
the monitor edges. Participants were asked to judge whether the target grating had been tilted clockwise
or anti-clockwise compared to the reference grating using the right and left arrow keys. Participants started
with a practice run of 10 trials for each of the four staircases. Participants then completed the experimental
run consisting of 140 trials for each staircase. The task nished when each staircase had reached eight
reversals and would be terminated if 140 trails were hit for each staircase.
To calculate OD thresholds, we used the nal six reversals from each staircase after discarding the
initial two reversals as practice trials. The thresholds of vertical and oblique conditions were calculated
separately by averaging each condition’s right (clockwise) and left (anti-clockwise) staircases.
Questionnaires
To assess autistic and schizotypal personality traits, we used the Autism Spectrum Quotient (AQ)
(Baron-Cohen et al., 2001) and the Schizotypal Personality Questionnaire-Brief Revised (SPQ-BR)
(Cohen et al., 2010). Both AQ and SPQ-BR scales were administered online using Qualtrics (https://www.
qualtrics.com).
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
Autism Spectrum Quotient (AQ)
The Autism Spectrum Quotient (AQ) is a 50-item self-report Quotient for measuring autistic
personality traits in the general population (Baron-Cohen et al., 2001). The items are scored on a 4-point
Likert scale with response options ranging from ‘denitely agree’ to ‘denitely disagree’. The responses are
collapsed into a dichotomous scoring scheme as responses with an endorsement of autistic personality
traits are scored 1 while the opposite responses are scored 0. The ve AQ subscales assess imagination,
attention to detail, communication, attention switching, and social skills subscales. The total score of AQ
ranges from 0-50 for the complete inventory, with a higher score indicative of a higher level of autistic
personality traits.
Schizotypal Personality Questionnaire-Brief Revised
The Schizotypal Personality Questionnaire-Brief Revised (SPQ-BR) is a 32-item self-report
questionnaire for measuring schizotypal personality traits (Cohen et al., 2010). The items are scored on a
5-point Likert scale with response options ranging from ‘strongly disagree’ to ‘strongly agree’. The SPQ-BR
consists of positive (i.e., “Cognitive-Perceptual”), negative (i.e., “Interpersonal”), and disorganised (i.e.,
“Disorganized”) subscales, with a total score ranging from 0 to 128 for the complete inventory whereby a
higher score is indicative of a higher level of schizotypal traits.
Exclusion Criteria
Three exclusion criteria were applied. One criterion was failing to reach six staircase reversals in
any condition of ODT. Another criterion was having OD thresholds with more than two standard deviations
(SD) away from the average (mean). The last criterion was failing to complete the survey. Data from 16
participants were excluded. Two participants failed to reach six staircase reversals in any ODT condition.
Also, the OD thresholds of six participants in any condition of ODT were more than 2 SD away from the
average. Additionally, eight participants did not complete the online survey, Tables 1 and 2.
Table 1. Illustrates the demographic information of 71 participants (46 female, 25 male) whose
data were included in the analyses after applying the exclusion criteria stated earlier.
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
Table 2. Illustrates each participant’s demographic information after applying the exclusion criteria
stated earlier
No. Sex Age AQ Score SPQ Score Vertical OD
Thresholds (°) Oblique OD
Thresholds (°)
1 F 26 28 103 0.95 7.01
2 F 36 28 127 3.80 11.63
3 F 24 27 77 0.94 4.45
4 F 18 26 92 0.80 5.66
5 F 20 26 85 2.28 8.69
6 F 24 26 98 1.81 3.89
7 F 28 26 72 0.64 6.97
8 F 21 26 106 1.80 6.89
9 F 26 25 97 2.29 6.71
10 F 18 24 112 2.82 8.61
11 F 22 24 93 1.95 7.77
12 F 29 24 93 2.62 9.63
13 F 25 23 112 3.95 7.37
14 F 22 22 66 4.03 13.26
15 F 19 21 105 2.29 7.75
16 F 19 21 80 2.34 9.71
17 F 34 21 76 3.00 7.05
18 F 25 21 81 2.40 6.05
19 F 23 20 87 3.14 10.7
20 F 20 19 92 1.48 5.96
21 F 21 18 96 4.36 8.65
22 F 20 17 106 4.46 9.61
23 F 20 16 86 1.90 10.31
24 F 18 16 103 1.82 8.15
25 F 18 16 74 1.27 10.93
26 F 28 16 56 1.37 11.71
27 F 19 16 63 2.04 8.28
28 F 37 16 84 0.53 4.69
29 F 19 16 65 0.89 6.09
30 F 18 15 90 1.35 13.52
31 F 27 15 77 1.12 5.33
32 F 27 15 75 0.93 7.29
33 F 18 14 73 0.91 9.00
34 F 18 13 100 1.13 9.48
35 F 19 13 79 1.02 5.27
36 F 21 13 88 1.61 8.81
37 F 23 13 86 0.50 6.84
38 F 18 12 92 3.93 7.32
39 F 18 12 65 1.78 8.97
40 F 18 10 88 2.48 7.14
41 F 23 10 69 2.03 8.48
42 F 26 10 65 0.58 4.55
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
43 F 18 8 73 2.43 13.00
44 F 33 8 104 2.53 9.88
45 F 19 7 56 1.72 10.21
46 F 18 7 77 2.04 10.50
47 M 18 37 106 1.77 6.13
48 M 19 36 115 2.93 10.25
49 M 27 32 66 0.90 4.97
50 M 19 29 96 0.55 4.40
51 M 20 29 95 0.60 4.20
52 M 31 26 101 0.90 3.25
53 M 20 24 58 1.41 7.21
54 M 19 24 103 1.02 6.47
55 M 19 22 94 0.82 8.48
56 M 32 21 57 1.57 9.07
57 M 19 21 86 0.98 3.93
58 M 28 20 101 1.27 6.69
59 M 26 19 94 1.10 8.29
60 M 20 18 91 1.33 7.84
61 M 20 18 95 0.96 6.69
62 M 20 18 71 1.29 5.20
63 M 19 17 81 1.92 9.39
64 M 22 17 79 4.91 11.3
65 M 22 15 80 0.65 4.46
66 M 18 14 99 1.50 8.28
67 M 21 14 71 0.86 7.75
68 M 22 14 71 1.33 8.77
69 M 30 14 61 0.67 6.93
70 M 21 12 64 0.98 9.14
71 M 19 6 64 0.78 4.01
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
Results
Data from 71 participants (46 female, 25 male; mean age 22.42; SD= 4.82; age range = 18–37) were
used to examine the relationship between ODT performance, autistic personality traits, and schizotypal
personality traits. The mean threshold of the vertical condition of ODT was 1.76° with a standard deviation
of 1.06°, while the mean threshold of the oblique condition of ODT was 7.80° with a standard deviation
of 2.38°. Paired sample t-test analysis showed a statistically signicant difference between vertical and
oblique ODT performance (t (70) =-24.88, p<.0001), Figure 2.
Figure 2. Mean orientation discrimination thresholds for the vertical and oblique conditions of the
orientation discrimination task. Error bars represent standard deviation. ***p < 0.0001.
AQ scores ranged from 6 to 37 (mean=18.83, SD=6.78), and SBQ-BR scores ranged from 56 to
127 (Mean=85.11, SD=16.21). The internal consistency analysis of both AQ and SPQ-BR scales revealed
high reliability, with Cronbach’s alpha of .80 for AQ and .85 for SPQ-BR.
To examine the relationship between performance in ODT, autistic personality traits, and schizotypal
personality traits, a Pearson correlation analysis was performed using the following variables: vertical OD
thresholds, oblique OD thresholds, AQ scores, and SPQ-BR scores.
We found a statistically signicant positive correlation between vertical OD thresholds and SPQ-
BR scores, (r= .304, n=71, p=.010). Higher vertical OD thresholds (worse task performance) correlated
with higher SPQ-BR scores, (Figure 3(a)). Also, we found a statistically signicant negative correlation
between oblique OD thresholds and AQ scores, (r= -.241, n=71, p=.043). Lower oblique OD thresholds
(better task performance) correlated with higher AQ scores, (Figure 3(b)). However, we found no signicant
correlation between vertical OD thresholds and AQ scores (r=.052, n=71, p=.33), nor was it between
oblique OD thresholds and SPQ-BR scores (r=-.036, n=71, p=.77).
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
Figure 3. (a) A correlation between vertical orientation discrimination thresholds and SPQ-BR
scores (r= .304, n=71 p=.010), and (b) A correlation between oblique orientation discrimination thresholds
and AQ scores (r= -.241, n=71 p=.043).
Additionally, the result showed that AQ scores positively correlated with SPQ-BR scores (r= .455,
n=71, p< .0001), (Figure 4).
Figure 4. A correlation between AQ scores and SPQ-BR scores (r= .455, n=71, p< .0001).
Furthermore, two partial correlation analyses were performed, given the correlational relationship
between AQ and SPQ-BR.
The rst partial correlation analysis was to assess the relationship between vertical OD thresholds
and SPQ-BR scores while controlling for AQ scores. The result revealed a statistically signicant positive
correlation between vertical OD thresholds and SPQ-BR scores when the AQ scores were controlled for
(r=.316 n=71, p=.008).
The second partial correlation analysis assessed the relationship between oblique OD thresholds
and AQ scores while controlling for the SPQ-BR scores. The result revealed a statistically negative
correlation between oblique OD thresholds and AQ scores when the SPQ-BR scores were controlled for
(r=-.253, n=71, p=.035).
In addition, to conrm that the associations between OD thresholds and scores in personality traits
were not driven by other possible factors such as age, which has been linked to cortical E-I balance in
previous studies (Abuleil, McCulloch and Thompson, 2019; King et al., 2020; Petitet et al., 2021; Pitchaiuthu
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
et al., 2017), further correlation analyses were performed. The results indicated no statistically signicant
correlation between age and both OD thresholds and personality traits, with p-values greater than .05,
Table 3. A possible explanation for the insignicant associations between age and other variables may be
due to the narrow range of age (18- 37 years).
Table 3. illustrates the correlations between age and both OD thresholds and scores
in personality traits.
Discussion
The current study aimed to replicate previous studies examining the relationship between
performance in ODT and autistic personality traits (Dickinson et al., 2015; Dickinson et al., 2014) nding
that higher levels of autistic personality traits were associated with lower thresholds in the oblique, but not
vertical, condition of ODT. In the same group of participants, we found that schizotypal personality traits
were linked to ODT performance in the vertical but not in the oblique condition, partially consistent with
the increased OD thresholds that have been found in a clinical sample of participants with SSC (Dickinson
et al., 2015; Dickinson et al., 2014), nding that higher levels of autistic traits were associated with lower
thresholds in the oblique, but not vertical, condition of ODT. In the same group of participants, we found
that schizotypal personality traits were linked to ODT performance in the vertical but not in the oblique
condition, partially consistent with the increased thresholds that have been found in a clinical sample of
participants with SSC (Shaw et al., 2019). Specically, individuals with higher schizotypal personality traits
showed increased OD thresholds (i.e., worse performance) in the vertical condition. Finally, we found that
higher autistic personality traits are associated with higher schizotypal personality traits, consistent with
previous ndings (Dinsdale et al., 2013; Ford et al., 2017; Ford and Crewther, 2014; Russell-Smith et al.,
2011).
As expected based on the hypothesis of increased inhibition in the ASC (Bonnel et al., 2010;
Bonnel et al., 2003; Dickinson, Bruyns-Haylett, et al., 2016; Dickinson et al., 2014), we found that high
autistic personality traits (indexed by high AQ scores) are associated with enhanced performance in
ODT (indexed by low OD thresholds). In line with previous results (Dickinson et al., 2015; Dickinson et
al., 2014), this association was condition-specic as it was only observed in the oblique ODT condition.
A possible explanation for the lack of a signicant relationship between autistic personality traits and
OD thresholds in the vertical condition has been attributed to the ceiling effect (Dickinson et al., 2014).
Compared to OD thresholds in the oblique condition (M=7.81°, SD=2.42°), OD thresholds in the vertical
condition were very low (M=1.78°, SD=1.05°), possibly preventing any potential performance differences
from being detectable (Garin, 2014a). Similar to this orientation-specic association between performance
in ODT and autistic personality traits, Edden et al. (2009) found that GABA concentration level in the visual
cortex was only signicantly associated with performance in the oblique condition of ODT but not with
that of vertical condition, possibly due to ceiling effect. Our nding of an association between high autistic
personality traits and enhanced performance in the oblique condition of ODT supports the suggestion of
increased cortical inhibition in the visual cortex of individuals with high autistic personality traits (Dickinson
et al., 2015; Dickinson et al., 2014).
Consistent with the hypothesis of disrupted E-I balance in the SSC (Abbasi et al., 2023; Anticevic
and Lisman, 2017; Lisman, 2012), the current study found an association between high schizotypal
personality traits (indexed by higher SPQ-BR score) and poor performance in ODT (indexed by high OD
thresholds). However, this association was only statistically signicant for the vertical condition of ODT
but not for the oblique condition. Such poor performance in the vertical condition of ODT may reect
decreased inhibition in the visual cortex, which has been suggested to be associated with SSC (Goto et
al., 2009; Rokem et al., 2011; Yoon et al., 2010; Yoon et al., 2009). For instance, reduced cortical inhibition
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Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
is associated with a broader orientation tuning curve of visual cortical neurons of individuals with SSC
(Rokem et al., 2011). As such, the lack of observing any signicant relationship between high schizotypal
personality traits and performance in the oblique condition of ODT might be due to the so-called ‘oor
effect’ (Garin, 2014b). This is because the visual orientation-tuning curve is initially broader for oblique
orientations than the vertical ones (Ringach, 1998), possibly limiting any further performance reduction
from being detectable.
Additionally, our nding of an association between high schizotypal personality traits and poorer
ODT performance is consistent with that of (Shaw et al., 2019) nding that individuals with SSC had
poorer ODT performance than NT individuals. However, it should be noted that (Shaw et al., 2019) found
that individuals with SSC had higher OD thresholds in both vertical and oblique conditions. Such partial
inconsistency could be related to the type of population. For example, while the study of (Shaw et al.,
2019) included a sample of clinically diagnosed individuals with SSC, our current study included a sample
of NT individuals with subclinical traits.
In line with previous studies (Dinsdale et al., 2013; Ford et al., 2017; Ford and Crewther, 2014;
Russell-Smith et al., 2011), we also found a signicant association between autistic and schizotypal
personality traits as high AQ scores are associated with high SPQ-BR scores. This is expected based
on previous studies showing an association between ASC and SSC (Burbach and van der Zwaag, 2009;
Chisholm et al., 2015; King and Lord, 2011; Pilowsky et al., 2000; Volkmar and Cohen, 1991; Wood,
2017). For instance, a systematic review and meta-analysis study examining the association between
ASC and SSC reported a 3.4% to 52% prevalence rate of ASC in individuals with SSC (Chisholm et
al., 2015). ASC and SSC have been characterised by defects in social, cognitive, and communication
functions (Pilowsky et al., 2000). Also, ASC and SSC have been suggested to share the same pathogenic
mechanism (Burbach and van der Zwaag, 2009). Additionally, our nding is consistent with previous
studies investigating the relationship between autistic personality traits and schizotypal personality
traits (Dinsdale et al., 2013; Ford et al., 2017; Ford and Crewther, 2014; Russell-Smith et al., 2011). For
instance, autistic personality traits and schizotypal personality traits of non-clinical participants were found
to be positively associated with each other (Dinsdale et al., 2013).
As previously reported (Dinsdale et al., 2013; Ford et al., 2017; Ford and Crewther, 2014; Nenadić
et al., 2021; Russell-Smith et al., 2011), AQ scores and SPQ-BR scores were correlated in the current
study. Given their association, the question arose as to how AQ scores and SPQ-BR scores could correlate
differentially with ODT performance. As is typical, the correlation between AQ scores and SPQ-BR scores
is below 1 in the current study (r=0.455), allowing the possibility for the scores of these two inventories
to independently and differentially correlate with ODT performance. To further investigate this possibility,
partial correlations were used to demonstrate that after controlling for AQ scores, the correlation between
SPQ-BR scores and vertical OD thresholds (r=.316) was similar to the zero-order correlation (r=.304).
Likewise, after controlling for SPQ-BR , the correlation between AQ scores and oblique OD thresholds
(r=-.253) was similar to zero-order correlation (r=-.241). This suggests that despite their association, AQ
scores and SPQ-BR correlate independently and differentially with ODT performance. Indeed, similar
ndings have been found for global versus local processing (Russell-Smith et al., 2010). Despite the
correlation between autistic and schizotypal traits, individuals with high autistic personality traits had an
advantage or preference for local versus global processing than those with low autistic personality traits
(Russell-Smith et al., 2010). However, individuals with high schizotypal personality traits were found to
have an advantage or preference for global versus local processing than those with low schizotypal
personality traits (Russell-Smith et al., 2010). Our divergent pattern of ndings regarding ODT performance
within the same sample is interesting. For instance, while ASC and SSC have been linked to enhanced
and impaired ODT performance, respectively (Dickinson, Bruyns-Haylett, et al., 2016; Shaw et al., 2019),
we show that these relationships remain present when studying these two types of traits within the same
sample. Our ndings may contribute unique mechanistic insight regarding E-I disruptions that cannot be
inferred when studying autistic and schizotypal samples independently.
Conclusion
The current study extended previous studies examining the relationship between performance in
ODT and autistic personality traits by examining schizotypal personality traits in the same sample. Similar
to previous studies (Dickinson et al., 2015; Dickinson et al., 2014), we found that higher levels of autistic
personality traits are associated with enhanced performance in the oblique condition of ODT. Additionally,
we found that high schizotypal personality traits are associated with poorer performance in the vertical
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385
Bin Dawood, A., Dickinson, A., & Jones, M. (2023). Investigation of the relationship between orientation discrimination
thresholds, autistic, and schizotypal personality traits, International Journal of Cognitive Research in Science, Engineering and
Education (IJCRSEE), 11(3), 375-387.
condition of ODT, as expected based on the ndings of (Shaw et al., 2019). Finally, we replicated the
previously demonstrated relationship between autistic and schizotypal personality traits (Dinsdale et al.,
2013; Ford et al., 2017). Future studies should examine such associations in different cultural contexts,
given the critical role of culture on cognition and mental health diagnoses (Banerjee, 2012; Kim, 2012;
Phillips, 2019).
Acknowledgements
This is a research project that was supported by a grant from the research centre for the College of
Education, Deanship of Scientic Research at King Saud University.
Conict of interests
The authors declare no conict of interest.
Author Contributions
ABD and MJ planned the experiment. AD developed and provided the software for the ODT. ABD
collected and analysed the data. MJ supervised the project. ABD wrote the manuscript, and MJ and AD
edited it. All authors reviewed the manuscript and agreed with the content.
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