David Hardwick | Griffith University (original) (raw)
Papers by David Hardwick
Clinical and Experimental Ophthalmology, 2002
An object briefly flashed adjacent to the path of another moving object appears to spatially lag ... more An object briefly flashed adjacent to the path of another moving object appears to spatially lag the moving object in the direction of its motion: the 'flash-lag effect'. A simple differential lag model account of this effect suggests that it occurs because the moving object activates motion detectors in the faster magnocellular pathway, whereas the flashed object does not. This model was tested by reducing M-pathway involvement using isoluminant stimuli. All four participants, who were university undergraduate students, were exposed to eight conditions, involving all possible combinations of moving and flashing objects coloured either white or green, shown against either a grey or a black background. Green objects were equiluminant with the grey background. The magnitude of the flash-lag effect was found using the method of constant stimuli. No reliable support was found for the hypothesis that equiluminance of the moving object reduces the flash-lag effect. Instead an interaction was found where there was an effect of equiluminance on the flash, but only when the moving object was not equiluminant. Such data is problematic for this and other simple differential lag models of the flash-lag effect.
Saccadic latency is reduced by a temporal gap between fixation point and target, by identificatio... more Saccadic latency is reduced by a temporal gap between fixation point and target, by identification of a target feature, and by movement in a new direction (inhibition of saccadic return, ISR). A simple additive model was compared with a shared resources model that predicts a three-way interaction. Twenty naive participants made horizontal saccades to targets left and right of fixation in a randomised block design. There was a significant three-way interaction among the factors on saccade latency. This was revealed in a two-way interaction between feature identification and the gap versus no gap factor which was only apparent when the saccade was in the same direction as the previous saccade. No interaction was apparent when the saccade was in the opposite direction. This result supports an attentional inhibitory effect that is present during ISR to a previous location which is only partly released by the facilitative effect of feature identification and gap. Together, anticipatory error data and saccade latency interactions suggest a source of ISR at a higher level of attention, possibly localised in the dorsolateral prefrontal cortex and involving tonic activation.
Vision Research, 2006
We report data from eight participants who made alignment judgements between a moving object and ... more We report data from eight participants who made alignment judgements between a moving object and a stationary, continuously visible 'landmark'. A reversing object had to overshoot the landmark by a significant amount in order to appear to reverse aligned with it. In addition, an adjacent flash irrelevant to the judgment task reliably increased this illusory 'foreshortening'. This and other results are most simply explained by a model in which the flash causes attentional capture, complemented by processes of temporal integration, or backward inhibition, and object representation. A flash used to probe the perception of a moving object's position disrupts that very perception.
Journal of Vision, Sep 23, 2005
Journal of Vision, Aug 22, 2003
Clinical and Experimental Ophthalmology, 2002
An object briefly flashed adjacent to the path of another moving object appears to spatially lag ... more An object briefly flashed adjacent to the path of another moving object appears to spatially lag the moving object in the direction of its motion: the 'flash-lag effect'. A simple differential lag model account of this effect suggests that it occurs because the moving object activates motion detectors in the faster magnocellular pathway, whereas the flashed object does not. This model was tested by reducing M-pathway involvement using isoluminant stimuli. All four participants, who were university undergraduate students, were exposed to eight conditions, involving all possible combinations of moving and flashing objects coloured either white or green, shown against either a grey or a black background. Green objects were equiluminant with the grey background. The magnitude of the flash-lag effect was found using the method of constant stimuli. No reliable support was found for the hypothesis that equiluminance of the moving object reduces the flash-lag effect. Instead an interaction was found where there was an effect of equiluminance on the flash, but only when the moving object was not equiluminant. Such data is problematic for this and other simple differential lag models of the flash-lag effect.
Clinical and Experimental Ophthalmology, 2002
An object briefly flashed adjacent to the path of another moving object appears to spatially lag ... more An object briefly flashed adjacent to the path of another moving object appears to spatially lag the moving object in the direction of its motion: the 'flash-lag effect'. A simple differential lag model account of this effect suggests that it occurs because the moving object activates motion detectors in the faster magnocellular pathway, whereas the flashed object does not. This model was tested by reducing M-pathway involvement using isoluminant stimuli. All four participants, who were university undergraduate students, were exposed to eight conditions, involving all possible combinations of moving and flashing objects coloured either white or green, shown against either a grey or a black background. Green objects were equiluminant with the grey background. The magnitude of the flash-lag effect was found using the method of constant stimuli. No reliable support was found for the hypothesis that equiluminance of the moving object reduces the flash-lag effect. Instead an interaction was found where there was an effect of equiluminance on the flash, but only when the moving object was not equiluminant. Such data is problematic for this and other simple differential lag models of the flash-lag effect.
Saccadic latency is reduced by a temporal gap between fixation point and target, by identificatio... more Saccadic latency is reduced by a temporal gap between fixation point and target, by identification of a target feature, and by movement in a new direction (inhibition of saccadic return, ISR). A simple additive model was compared with a shared resources model that predicts a three-way interaction. Twenty naive participants made horizontal saccades to targets left and right of fixation in a randomised block design. There was a significant three-way interaction among the factors on saccade latency. This was revealed in a two-way interaction between feature identification and the gap versus no gap factor which was only apparent when the saccade was in the same direction as the previous saccade. No interaction was apparent when the saccade was in the opposite direction. This result supports an attentional inhibitory effect that is present during ISR to a previous location which is only partly released by the facilitative effect of feature identification and gap. Together, anticipatory error data and saccade latency interactions suggest a source of ISR at a higher level of attention, possibly localised in the dorsolateral prefrontal cortex and involving tonic activation.
Vision Research, 2006
We report data from eight participants who made alignment judgements between a moving object and ... more We report data from eight participants who made alignment judgements between a moving object and a stationary, continuously visible 'landmark'. A reversing object had to overshoot the landmark by a significant amount in order to appear to reverse aligned with it. In addition, an adjacent flash irrelevant to the judgment task reliably increased this illusory 'foreshortening'. This and other results are most simply explained by a model in which the flash causes attentional capture, complemented by processes of temporal integration, or backward inhibition, and object representation. A flash used to probe the perception of a moving object's position disrupts that very perception.
Journal of Vision, Sep 23, 2005
Journal of Vision, Aug 22, 2003
Clinical and Experimental Ophthalmology, 2002
An object briefly flashed adjacent to the path of another moving object appears to spatially lag ... more An object briefly flashed adjacent to the path of another moving object appears to spatially lag the moving object in the direction of its motion: the 'flash-lag effect'. A simple differential lag model account of this effect suggests that it occurs because the moving object activates motion detectors in the faster magnocellular pathway, whereas the flashed object does not. This model was tested by reducing M-pathway involvement using isoluminant stimuli. All four participants, who were university undergraduate students, were exposed to eight conditions, involving all possible combinations of moving and flashing objects coloured either white or green, shown against either a grey or a black background. Green objects were equiluminant with the grey background. The magnitude of the flash-lag effect was found using the method of constant stimuli. No reliable support was found for the hypothesis that equiluminance of the moving object reduces the flash-lag effect. Instead an interaction was found where there was an effect of equiluminance on the flash, but only when the moving object was not equiluminant. Such data is problematic for this and other simple differential lag models of the flash-lag effect.