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Apthorp, Deborah
- PublicationSocial and attention-to-detail subclusters of autistic traits differentially predict looking at eyes and face identity recognition ability(John Wiley & Sons Ltd, 2017-02)
; Palermo, RominaThis study distinguished between different subclusters of autistic traits in the general population and examined the relationships between these subclusters, looking at the eyes of faces, and the ability to recognize facial identity. Using the Autism Spectrum Quotient (AQ) measure in a university-recruited sample, we separate the social aspects of autistic traits (i.e., those related to communication and social interaction; AQ-Social) from the non-social aspects, particularly attention-to-detail (AQ-Attention). We provide the first evidence that these social and non-social aspects are associated differentially with looking at eyes: While AQ-Social showed the commonly assumed tendency towards reduced looking at eyes, AQ-Attention was associated with increased looking at eyes. We also report that higher attention-to-detail (AQ-Attention) was then indirectly related to improved face recognition, mediated by increased number of fixations to the eyes during face learning. Higher levels of socially relevant autistic traits (AQ-Social) trended in the opposite direction towards being related to poorer face recognition (significantly so in females on the Cambridge Face Memory Test). There was no evidence of any mediated relationship between AQ-Social and face recognition via reduced looking at the eyes. These different effects of AQ-Attention and AQ-Social suggest face-processing studies in Autism Spectrum Disorder might similarly benefit from considering symptom subclusters. Additionally, concerning mechanisms of face recognition, our results support the view that more looking at eyes predicts better face memory. - PublicationBertamini, M. Programming Visual Illusions for Everyone. Cham, Switzerland: Springer, 2018; 221 pp.: ISBN 9783319640655, £24.99 Hardback.Some years ago, as a vision science Honours and then PhD student emerging from a Psychology degree (as many of us do), I had no programming experience at all when I started to run my experiments. This was before the days of PsychoPy, so I ran everything in MATLAB, first of all relying on my supervisor to program the experiments and then, over the years, teaching myself the necessary programming skills.
- PublicationLocation of the interaction between motion and form signals in motion-streak facilitation
Introduction. Motion streaks are the smeared representation of a moving object produced by the response persistence of cortical cells. They can be treated as form cues by the visual system, and can facilitate motion processing (Geisler, 1999, Nature). Here we investigated where in the visual system this interaction between form and motion signals occurs. Two likely candidates are the local (V1) and global (V5/MT or MSTd) motion levels. Methods. We used a three-frame global-motion stimulus consisting of signal and noise dots. Strong or weak motion streaks were generated by moving a given dot in either the same direction or a different direction on each frame transition, respectively. There were three conditions: 1) No strong motion-streaks (No Streak)" 2) Strong streaks on the signal (Signal Streak)" 3) strong streaks on the noise (Noise Streak). Thresholds were the percentage of signal dots required to perform a 2AFC direction judgement. The Noise-Streak condition was designed to tap differences in the tuning of cells at the local- and global-motion levels. At the global-motion level, cells are tuned to particular signal directions, so motion streaks should enhance the motion response only when they are in that signal direction, so this would not occur in the Noise-Streak condition. At the local-motion level, each cell is tuned to the direction it is extracting, so if the form-motion interaction occurs here, the noise strength in the Noise-Streak condition would be enhanced. Results. Thresholds for the Signal Streak condition were the lowest (consistent with Edwards & Crane, 2007, VisRes) and thresholds for Noise-Streak condition were the highest. Conclusions. Strong streaks in Noise-Streak impaired motion extraction, consistent with those streaks enhancing the strength of those noise motion-signals. This finding supports the form and motion interactions in motion streak facilitation occurring at the local-motion level.
- PublicationThe Shepard-Risset glissando: music that moves youSounds are thought to contribute to the perceptions of self-motion, often via higher-level, cognitive mechanisms. This study examined whether illusory self-motion (i.e. vection) could be induced by auditory metaphorical motion stimulation (without providing any spatialized or low-level sensory information consistent with self-motion). Five different types of auditory stimuli were presented in mono to our 20 blindfolded, stationary participants (via a loud speaker array): (1) an ascending Shepard-Risset glissando; (2) a descending Shepard-Risset glissando; (3) a combined Shepard-Risset glissando; (4) a combined-adjusted (loudness-controlled) Shepard-Risset glissando; and (5) a white-noise control stimulus. We found that auditory vection was consistently induced by all four Shepard-Risset glissandi compared to the white-noise control. This metaphorical auditory vection appeared similar in strength to the vection induced by the visual reference stimulus simulating vertical self-motion. Replicating past visual vection findings, we also found that individual differences in postural instability appeared to significantly predict auditory vection strength ratings. These findings are consistent with the notion that auditory contributions to self-motion perception may be predominantly due to higher-level cognitive factors.
- PublicationTilt aftereffects and tilt illusions induced by fast translational motion: Evidence for motion streaksFast-moving visual features are thought to leave neural ‘streaks’ that can be detected by orientation-selective cells. Here, we tested whether ‘motion streaks’ can induce classic tilt aftereffects (TAEs) and tilt illusions (TIs). For TAEs, participants adapted to random arrays of small Gaussian blobs drifting at 9.5 deg/s. Following adaptation to directions of 15, 30, 45, 60, 75, and 90 degrees (clockwise from vertical) subjective vertical was measured for a briefly presented test grating. For TIs, the same motions were presented in an annular surround and subjective vertical was measured for a simultaneously presented central grating. All motions were 50% coherent, with half the blobs following random-walk paths and half following a fixed direction. Strong and weak streaks were compared by varying streak length (the number of fixed-walk frames), rather than by manipulating speed, so that speed and coherence were matched in all conditions. Strong motion streaks produced robust TAEs and TIs, similar in magnitude and orientation tuning to those induced by tilted lines. These effects were weak or absent in weak streak conditions, and when motion was too slow to form streaks. Together, these results indicate that motion streaks produced by temporal integration of fast translating features do effectively adapt orientation-selective cells and may therefore be exploited to improve perception of motion direction as described in the ‘motion streaks’ model.
- PublicationAnisotropies in judging the direction of moving natural scenes(Association for Research in Vision and Ophthalmology, 2010-09-03)
; Alais, DavidAlthough visual systems are optimized to deal with the natural visual environment, our understanding of human motion perception is in large part based on the use of artificial stimuli. Here, we assessed observers' ability to estimate the direction of translating natural images and fractals by having them adjust the orientation of a subsequently viewed line. A system of interleaved staircases, driven by observers' direction estimates, ensured that stimuli were presented near one of 16 reference directions. The resulting error distributions (i.e., the differences between reported and true directions) reveal several anisotropies in global motion processing. First, observers' estimates are biased away from cardinal directions (reference repulsion). Second, the standard deviations of estimates show an “oblique effect” being ~45% lower around cardinal directions. Third, errors around cardinal directions are more likely (~22%) to approach zero than would be consistent with Gaussian-distributed errors, suggesting that motion processing minimizes the number as well as magnitude of errors. Fourth, errors are similar for natural scenes and fractals, indicating that observers do not use top-down information to improve performance. Finally, adaptation to unidirectional motion modifies observers' bias by amplifying existing repulsion (e.g., around cardinal directions). This bias change can improve direction discrimination but is not due to a reduction in variability. - PublicationThe role of Weber's law in human time perceptionWeber's law predicts that stimulus sensitivity will increase proportionally with increases in stimulus intensity. Does this hold for the stimulus of time - specifically, duration in the milliseconds to seconds range? There is conflicting evidence on the relationship between temporal sensitivity and duration. Weber's law predicts a linear relationship between sensitivity and duration on interval timing tasks, while two alternative models predict a reverse J-shaped and a U-shaped relationship. Based on previous research, we hypothesised that temporal sensitivity in humans would follow a U-shaped function, increasing and then decreasing with increases in duration, and that this model would provide a better statistical fit to the data than the reverse-J or the simple Weber's Law model. In a two-alternative forced-choice interval comparison task, 24 participants made duration judgements about six groups of auditory intervals between 100 and 3,200 ms. Weber fractions were generated for each group of intervals and plotted against time to generate a function describing sensitivity to the stimulus of duration. Although the sensitivity function was slightly concave, and the model describing a U-shaped function gave the best fit to the data, the increase in the model fit was not sufficient to warrant the extra free parameter in the chosen model. Further analysis demonstrated that Weber's law itself provided a better description of sensitivity to changes in duration than either of the two models tested.
- PublicationWhat's in a Badge? A Computational Reproducibility Investigation of the Open Data Badge Policy in One Issue of Psychological Science(Sage Publications, Inc, 2023)
; In April 2019, Psychological Science published its first issue in which all Research Articles received the Open Data badge. We used that issue to investigate the effectiveness of this badge, focusing on the adherence to its aim at Psychological Science: sharing both data and code to ensure reproducibility of results. Twelve researchers of varying experience levels attempted to reproduce the results of the empirical articles in the target issue (at least three researchers per article). We found that all 14 articles provided at least some data and six provided analysis code, but only one article was rated to be exactly reproducible, and three were rated as essentially reproducible with minor deviations. We suggest that researchers should be encouraged to adhere to the higher standard in force at Psychological Science. Moreover, a check of reproducibility during peer review may be preferable to the disclosure method of awarding badges.
- PublicationPostural sway as a measure of disease severity in parkinson's disease(BMJ Group, 2018-06)
; Introduction The severity of Parkinson's disease (PD) is difficult to assess accurately owing to the lack of a robust biological marker of disease progression, with consequent implications for prognosis and treatment. The current standard measure is the Unified Parkinson's Disease Rating Scale (UPDRS) but this is hampered by considerable variability between observers and within subjects. Postural sway correlates well with complex brain functioning in other conditions. This study aimed to investigate the correlation of postural sway with the UPDRS and other non-motor measures of disease severity in patients with PD.
- PublicationThe spatial tuning of "motion streak" mechanisms revealed by masking and adaptation(Association for Research in Vision and Ophthalmology, 2011-06)
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