Martin Lages | University of Glasgow (original) (raw)
Papers by Martin Lages
Psychiatry, Psychology and Law, 2021
The Scottish verdict of not proven represents a second acquittal verdict which is not legally def... more The Scottish verdict of not proven represents a second acquittal verdict which is not legally defined. Existing research into the influence of the not proven verdict on jury decision making is modest. The main aim of the current study was therefore to investigate the influence of verdict systems (two vs three) on juror decision making. The effect of pre-trial bias and evidence anchors on juror judgements were also examined. One-hundred and twenty-eight mock jurors listened to two homicide vignettes and were asked to rate their belief of guilt of the accused and to give a verdict in both trials. The results suggest that pretrial bias was a significant predictor of both verdict choice and belief of guilt, whereas evidence anchors were not a significant predictor of either. Finally, both guilty and not guilty verdicts were given with increased frequency in the two-verdict system when compared to the three-verdict system.
Frontiers in Psychology, 2012
In two replication studies we examined response bias and dependencies in voluntary decisions. We ... more In two replication studies we examined response bias and dependencies in voluntary decisions. We trained a linear classifier to predict "spontaneous decisions" and in the second study "hidden intentions" from responses in preceding trials and achieved comparable prediction accuracies as reported for multivariate pattern classification based on voxel activities in frontopolar cortex. We discuss implications of our findings and suggest ways to improve classification analyses of fMRI BOLD signals that may help to reduce effects of response dependencies between trials.
Vision Research, 2003
We used the Pulfrich effect to investigate perception of motion in depth. Independent manipulatio... more We used the Pulfrich effect to investigate perception of motion in depth. Independent manipulation of spatial and temporal frequency content in stereoscopic motion stimuli revealed the tuning characteristics of motion-in-depth perception. Sensitivity to interocular phase difference between sinusoidally oscillating sine-wave gratings was measured in four observers who judged direction of motion in depth. Discrimination thresholds in terms of interocular phase difference were determined to investigate spatial and temporal tuning characteristics of a system that is based on interocular phase difference, interocular delay, binocular disparity and velocity difference. Temporal frequency tuning of interocular phase difference thresholds was band pass and relatively dependent on spatial frequency variation. These results together with evidence from two control experiments support the idea that sensitivity to direction of motion in depth is limited by a stereo-motion system that monitors binocular horizontal disparity and motion rather than interocular phase difference, interocular delay, or interocular velocity difference.
Journal of Vision, 2009
Motion-induced blindness (MIB) describes the occasional disappearance of salient visual objects i... more Motion-induced blindness (MIB) describes the occasional disappearance of salient visual objects in the presence of moving features (Y. S. Bonneh, A. Cooperman, & D. Sagi, 2001). Here we test whether motion adaptation and the ensuing motion aftereffect (MAE) are sufficient to trigger disappearance of salient targets. In three experiments, observers adapted to either rotating or static stimuli. Immediately afterwards, a static test pattern was presented consisting of a mask with texture elements and three superimposed target dots in a triangular arrangement. Observers reported dot disappearance and reappearance. The results clearly show that illusory motion in a static test pattern, following motion adaptation, promotes the disappearance of target dots. Furthermore, disappearance is modulated by the depth relationship between test pattern and targets, increasing for targets placed stereoscopically behind the test pattern. We conclude that MIB is influenced by perceived relative motion between depth-segregated features.
Behavioral Sciences & the Law
Proven and not proven: A potential alternative to the current Scottish verdict system. Behavioral... more Proven and not proven: A potential alternative to the current Scottish verdict system. Behavioral Sciences & the Law (Early access). For guidance on citations see FAQs.
Psychological Reports, 2022
In several studies, it has been suggested that task-switching performance is linked to processing... more In several studies, it has been suggested that task-switching performance is linked to processing speed. Here we argue that the relation between processing speed and high-level cognitive ability found in previous studies may be due to confounded measurements of processing speed and task-switching ability. In the present study, we required participants to complete an inspection time (IT) task to probe their processing speed. We employed conventional task-switching paradigms but applied a linear integrated speed-accuracy score (LISAS) which combines latency and accuracy scores to express task-switching ability. The results of regression analyses show that IT predicted average performance in task-switching paradigms. However, IT did not relate to any specific effects common in the task-switching task, which contradicts previous results. Our results suggest independent mechanisms of processing speed and tasks that require a high level of cognitive flexibility and control.
Gaussian signal detection models with equal variance are typically used in yes-no detection and d... more Gaussian signal detection models with equal variance are typically used in yes-no detection and discrimination whereas models with unequal variance require paradigms with multiple response categories or conditions. Here, a hierarchical signal detection model with unequal variance is proposed that is based on binary responses from a sample of participants. Introducing plausible constraints on sampling distributions makes it possible to estimate sensitivity, decision criterion and signal variance at the population level. The model is explored in simulation studies and applied to existing data from memory and reasoning tasks. The results suggest that this hierarchical unequal-variance model provides a promising alternative to equal-variance models.
Journal of Experimental Psychology: Learning, Memory, and Cognition, 2019
Acta Psychologica, 2019
Previous research has shown that there are significant task-switching costs even when participant... more Previous research has shown that there are significant task-switching costs even when participants have time to prepare for task switching after cueing. We investigated individual differences in task switching by monitoring errors and response times of individual participants. In Experiment 1A, 58 participants were encouraged to finish the session early by completing 200 consecutive trials without making an error. In case of a mistake, they had to repeat their effort until the experimental session expired. Using this demanding procedure, 16 participants managed to complete early. Among these 16 we identified 9 best performers who showed no significant switch costs. We conducted follow-up Experiment 1B on these best performers by systematically varying cue-stimulus intervals and inter-trial intervals. The results confirmed that these participants had no significant RT and ER switch costs when they had time to prepare the task between cue and target onset. However, significant switch costs emerged when cue and target stimulus were presented simultaneously. In Experiment 1C, using three classical task-switching paradigms, we compared the best performers with 9 controls who had made frequent errors in Experiment 1A. Although the best performers responded faster and made fewer errors, they only showed reduced switch costs in a pre-cued paradigm that had been extensively practiced. In two other paradigms with simultaneous presentation of cue and target stimulus, best performers had switch costs and showed considerable individual differences similar to the controls. We conclude that there are considerable individual differences in task switching and that smaller individual switch costs are mainly related to efficient task preparation. We speculate that efficient task preparation may be linked to better executive control and general intelligence.
Frontiers in Psychology, 2013
Frontiers in Psychology, 2019
In task-switching experiments with bivalent target stimuli, conflicts during response selection g... more In task-switching experiments with bivalent target stimuli, conflicts during response selection give rise to response-congruency effects. Typically, participants respond more slowly and make more errors in trials with incongruent targets that require different responses in the two tasks, compared to trials with congruent targets that are associated with the same response in both tasks. Here we investigate whether participants show response-congruency effects when task rules are not made explicit. In two experiments, we assigned task-irrelevant features to each bivalent target. When participants were instructed to apply the task rules, they showed significant taskswitching costs as well as response-congruency effects. Importantly, when the same participants did not know the task rules and responded without applying the task rules, they showed response-congruency effects but no switch costs. The significant congruency effects suggest that associations between bivalent target features and responses can be formed passively, even when participants do not follow the task rules and use task-irrelevant target features to make a response.
Geometric constraints for the perception of three-dimensional (3D) binocular motion are discussed... more Geometric constraints for the perception of three-dimensional (3D) binocular motion are discussed in a probabilistic framework. Two alternative Bayesian models of binocular integration are put forward to explain perceptual bias under uncertainty. The models exploit biologically plausible constraints of local motion and disparity processing in a binocular viewing geometry. Results from computer simulations and model selection support the idea that disparity processing rather than motion processing introduces perceptual bias in 3D motion. This suggests that the binocular motion system combines motion and disparity constraints relatively late when establishing a 3D motion percept.
Journal of vision, 2006
Psychophysical studies on three-dimensional (3-D) motion perception have shown that perceived tra... more Psychophysical studies on three-dimensional (3-D) motion perception have shown that perceived trajectory angles of a small target traveling in depth are systematically biased. Here, predictions from Bayesian models, which extend existing models of motion-first and stereo-first processing, are investigated. These statistical models are based on stochastic representations of monocular velocity and binocular disparity input in a binocular viewing geometry. The assumption of noise in these inputs together with a plausible prior for 3-D motion leads to testable predictions of perceived trajectory angle and velocity. Results from two experiments are reported, suggesting that disparity rather than motion processing introduces perceptual bias.
Psychological science, 2017
Visual performance of human observers depends not only on the optics of the eye and early sensory... more Visual performance of human observers depends not only on the optics of the eye and early sensory encoding but also on subsequent cortical processing and representations. In two experiments, we demonstrated that motion adaptation can enhance as well as impair visual acuity. Observers who experienced an expanding motion aftereffect exhibited improved letter recognition, whereas observers who experienced a contracting motion aftereffect showed impaired letter recognition. We conclude that illusory enlargement and shrinkage of a visual stimulus can modulate visual acuity.
Human information processing: Vision, memory, and attention., 2013
We propose a new adaptive novelty detection based algorithm for the primary local recognition of ... more We propose a new adaptive novelty detection based algorithm for the primary local recognition of images corrupted by multiplicative/additive and impulse noise. The purpose of primary local recognition or low level analysis such as segmentation, small object and outlier detection is to provide a representation which could be potentially used e.g. in context based classification or nonlinear denoising techniques. The method is based on the estimation of mixing parameters (priors) of probabilistic mixture models along a small sliding window. A novelty score is defined by the mixing parameters and this is utilized by the procedure for determining the corresponding class of image patch with the aid of a lookup table. Numerical simulations demonstrate that the proposed method is able to improve upon previously employed techniques for the \r\nsame task. In addition, the computational demand required by the proposed method is clearly inferior to some of the recently applied techniques as ex...
Interdisciplinary Concepts, 2013
Interdisciplinary Concepts, 2013
Forensic Science International: Synergy
Psychiatry, Psychology and Law, 2021
The Scottish verdict of not proven represents a second acquittal verdict which is not legally def... more The Scottish verdict of not proven represents a second acquittal verdict which is not legally defined. Existing research into the influence of the not proven verdict on jury decision making is modest. The main aim of the current study was therefore to investigate the influence of verdict systems (two vs three) on juror decision making. The effect of pre-trial bias and evidence anchors on juror judgements were also examined. One-hundred and twenty-eight mock jurors listened to two homicide vignettes and were asked to rate their belief of guilt of the accused and to give a verdict in both trials. The results suggest that pretrial bias was a significant predictor of both verdict choice and belief of guilt, whereas evidence anchors were not a significant predictor of either. Finally, both guilty and not guilty verdicts were given with increased frequency in the two-verdict system when compared to the three-verdict system.
Frontiers in Psychology, 2012
In two replication studies we examined response bias and dependencies in voluntary decisions. We ... more In two replication studies we examined response bias and dependencies in voluntary decisions. We trained a linear classifier to predict "spontaneous decisions" and in the second study "hidden intentions" from responses in preceding trials and achieved comparable prediction accuracies as reported for multivariate pattern classification based on voxel activities in frontopolar cortex. We discuss implications of our findings and suggest ways to improve classification analyses of fMRI BOLD signals that may help to reduce effects of response dependencies between trials.
Vision Research, 2003
We used the Pulfrich effect to investigate perception of motion in depth. Independent manipulatio... more We used the Pulfrich effect to investigate perception of motion in depth. Independent manipulation of spatial and temporal frequency content in stereoscopic motion stimuli revealed the tuning characteristics of motion-in-depth perception. Sensitivity to interocular phase difference between sinusoidally oscillating sine-wave gratings was measured in four observers who judged direction of motion in depth. Discrimination thresholds in terms of interocular phase difference were determined to investigate spatial and temporal tuning characteristics of a system that is based on interocular phase difference, interocular delay, binocular disparity and velocity difference. Temporal frequency tuning of interocular phase difference thresholds was band pass and relatively dependent on spatial frequency variation. These results together with evidence from two control experiments support the idea that sensitivity to direction of motion in depth is limited by a stereo-motion system that monitors binocular horizontal disparity and motion rather than interocular phase difference, interocular delay, or interocular velocity difference.
Journal of Vision, 2009
Motion-induced blindness (MIB) describes the occasional disappearance of salient visual objects i... more Motion-induced blindness (MIB) describes the occasional disappearance of salient visual objects in the presence of moving features (Y. S. Bonneh, A. Cooperman, & D. Sagi, 2001). Here we test whether motion adaptation and the ensuing motion aftereffect (MAE) are sufficient to trigger disappearance of salient targets. In three experiments, observers adapted to either rotating or static stimuli. Immediately afterwards, a static test pattern was presented consisting of a mask with texture elements and three superimposed target dots in a triangular arrangement. Observers reported dot disappearance and reappearance. The results clearly show that illusory motion in a static test pattern, following motion adaptation, promotes the disappearance of target dots. Furthermore, disappearance is modulated by the depth relationship between test pattern and targets, increasing for targets placed stereoscopically behind the test pattern. We conclude that MIB is influenced by perceived relative motion between depth-segregated features.
Behavioral Sciences & the Law
Proven and not proven: A potential alternative to the current Scottish verdict system. Behavioral... more Proven and not proven: A potential alternative to the current Scottish verdict system. Behavioral Sciences & the Law (Early access). For guidance on citations see FAQs.
Psychological Reports, 2022
In several studies, it has been suggested that task-switching performance is linked to processing... more In several studies, it has been suggested that task-switching performance is linked to processing speed. Here we argue that the relation between processing speed and high-level cognitive ability found in previous studies may be due to confounded measurements of processing speed and task-switching ability. In the present study, we required participants to complete an inspection time (IT) task to probe their processing speed. We employed conventional task-switching paradigms but applied a linear integrated speed-accuracy score (LISAS) which combines latency and accuracy scores to express task-switching ability. The results of regression analyses show that IT predicted average performance in task-switching paradigms. However, IT did not relate to any specific effects common in the task-switching task, which contradicts previous results. Our results suggest independent mechanisms of processing speed and tasks that require a high level of cognitive flexibility and control.
Gaussian signal detection models with equal variance are typically used in yes-no detection and d... more Gaussian signal detection models with equal variance are typically used in yes-no detection and discrimination whereas models with unequal variance require paradigms with multiple response categories or conditions. Here, a hierarchical signal detection model with unequal variance is proposed that is based on binary responses from a sample of participants. Introducing plausible constraints on sampling distributions makes it possible to estimate sensitivity, decision criterion and signal variance at the population level. The model is explored in simulation studies and applied to existing data from memory and reasoning tasks. The results suggest that this hierarchical unequal-variance model provides a promising alternative to equal-variance models.
Journal of Experimental Psychology: Learning, Memory, and Cognition, 2019
Acta Psychologica, 2019
Previous research has shown that there are significant task-switching costs even when participant... more Previous research has shown that there are significant task-switching costs even when participants have time to prepare for task switching after cueing. We investigated individual differences in task switching by monitoring errors and response times of individual participants. In Experiment 1A, 58 participants were encouraged to finish the session early by completing 200 consecutive trials without making an error. In case of a mistake, they had to repeat their effort until the experimental session expired. Using this demanding procedure, 16 participants managed to complete early. Among these 16 we identified 9 best performers who showed no significant switch costs. We conducted follow-up Experiment 1B on these best performers by systematically varying cue-stimulus intervals and inter-trial intervals. The results confirmed that these participants had no significant RT and ER switch costs when they had time to prepare the task between cue and target onset. However, significant switch costs emerged when cue and target stimulus were presented simultaneously. In Experiment 1C, using three classical task-switching paradigms, we compared the best performers with 9 controls who had made frequent errors in Experiment 1A. Although the best performers responded faster and made fewer errors, they only showed reduced switch costs in a pre-cued paradigm that had been extensively practiced. In two other paradigms with simultaneous presentation of cue and target stimulus, best performers had switch costs and showed considerable individual differences similar to the controls. We conclude that there are considerable individual differences in task switching and that smaller individual switch costs are mainly related to efficient task preparation. We speculate that efficient task preparation may be linked to better executive control and general intelligence.
Frontiers in Psychology, 2013
Frontiers in Psychology, 2019
In task-switching experiments with bivalent target stimuli, conflicts during response selection g... more In task-switching experiments with bivalent target stimuli, conflicts during response selection give rise to response-congruency effects. Typically, participants respond more slowly and make more errors in trials with incongruent targets that require different responses in the two tasks, compared to trials with congruent targets that are associated with the same response in both tasks. Here we investigate whether participants show response-congruency effects when task rules are not made explicit. In two experiments, we assigned task-irrelevant features to each bivalent target. When participants were instructed to apply the task rules, they showed significant taskswitching costs as well as response-congruency effects. Importantly, when the same participants did not know the task rules and responded without applying the task rules, they showed response-congruency effects but no switch costs. The significant congruency effects suggest that associations between bivalent target features and responses can be formed passively, even when participants do not follow the task rules and use task-irrelevant target features to make a response.
Geometric constraints for the perception of three-dimensional (3D) binocular motion are discussed... more Geometric constraints for the perception of three-dimensional (3D) binocular motion are discussed in a probabilistic framework. Two alternative Bayesian models of binocular integration are put forward to explain perceptual bias under uncertainty. The models exploit biologically plausible constraints of local motion and disparity processing in a binocular viewing geometry. Results from computer simulations and model selection support the idea that disparity processing rather than motion processing introduces perceptual bias in 3D motion. This suggests that the binocular motion system combines motion and disparity constraints relatively late when establishing a 3D motion percept.
Journal of vision, 2006
Psychophysical studies on three-dimensional (3-D) motion perception have shown that perceived tra... more Psychophysical studies on three-dimensional (3-D) motion perception have shown that perceived trajectory angles of a small target traveling in depth are systematically biased. Here, predictions from Bayesian models, which extend existing models of motion-first and stereo-first processing, are investigated. These statistical models are based on stochastic representations of monocular velocity and binocular disparity input in a binocular viewing geometry. The assumption of noise in these inputs together with a plausible prior for 3-D motion leads to testable predictions of perceived trajectory angle and velocity. Results from two experiments are reported, suggesting that disparity rather than motion processing introduces perceptual bias.
Psychological science, 2017
Visual performance of human observers depends not only on the optics of the eye and early sensory... more Visual performance of human observers depends not only on the optics of the eye and early sensory encoding but also on subsequent cortical processing and representations. In two experiments, we demonstrated that motion adaptation can enhance as well as impair visual acuity. Observers who experienced an expanding motion aftereffect exhibited improved letter recognition, whereas observers who experienced a contracting motion aftereffect showed impaired letter recognition. We conclude that illusory enlargement and shrinkage of a visual stimulus can modulate visual acuity.
Human information processing: Vision, memory, and attention., 2013
We propose a new adaptive novelty detection based algorithm for the primary local recognition of ... more We propose a new adaptive novelty detection based algorithm for the primary local recognition of images corrupted by multiplicative/additive and impulse noise. The purpose of primary local recognition or low level analysis such as segmentation, small object and outlier detection is to provide a representation which could be potentially used e.g. in context based classification or nonlinear denoising techniques. The method is based on the estimation of mixing parameters (priors) of probabilistic mixture models along a small sliding window. A novelty score is defined by the mixing parameters and this is utilized by the procedure for determining the corresponding class of image patch with the aid of a lookup table. Numerical simulations demonstrate that the proposed method is able to improve upon previously employed techniques for the \r\nsame task. In addition, the computational demand required by the proposed method is clearly inferior to some of the recently applied techniques as ex...
Interdisciplinary Concepts, 2013
Interdisciplinary Concepts, 2013
Forensic Science International: Synergy