Professor Angus Gellatly
Emeritus Professor of Psychology
School of Psychology, Social Work and Public Health
Role
Emeritus Professor Angus Gellatly’s research interests are in cognitive psychology broadly conceived. Over the years they have included memory, reasoning, ergonomics and cognitive development. He has also explored how the sociology of knowledge can be applied to psychological knowledge claims and has been particularly concerned with how attributions of cognitive competence are or are not made to humans, animals and machines.
The focus of his current research interest is in visual cognition. He has had recent ESRC grants to investigate visual attention and visual masking. The aim of this work is to understand the processes involved in deriving a representation of the environment in terms of objects and background, and how these processes influence and are influenced by different forms of visual attention. Or, put more simply, why you usually do but sometimes don't see what's in front of you!
Research
Publications
Journal articles
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Pilling M, Gellatly A, 'The influence of absolute and relative spatial cues on change detection performance'
Visual Cognition [in press] (2024)
ISSN: 1350-6285 eISSN: 1464-0716AbstractOpen Access on RADARTwo experiments investigate how absolute and relative spatial cues influence perceptual comparisons between visual short-term memory (VSTM) and current vision. The core question concerned the role of task demands in this process. Two tasks were given across two experiments, differing in the extent they required object-level comparisons. Experiment 1, a feature comparison task, required reporting if any new colour was present in the second of two interleaved displays of four colours inside a surround; Experiment 2, an object comparison task, required report of any changes in colour-shape pairings in the second of two interleaved displays of four coloured shapes in a surround. Absolute and relative spatial organization was manipulated in both experiments by presenting compared displays on the same or contralateral sides, and by having the second display items in the same locations within the surround, in new locations, or repositioned into previous locations of other items. In sensitivity, both tasks showed an advantage for absolute spatial cues, but only the object task showed an advantage for relative spatial cues. In bias, both tasks were similarly influenced by both absolute and relative cues. Results suggest relative spatial cues are always available but only used when making object-level comparisons.
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Pilling M, Barrett DJK, Gellatly A, 'The basis of report-difference superiority in delayed perceptual comparison tasks'
Memory & Cognition 48 (2020) pp.856-869
ISSN: 0090-502X eISSN: 1532-5946AbstractPublished here Open Access on RADARA major role for visual short-term memory (VSTM) is to mediate perceptual comparisons of visual information across successive glances and brief temporal interruptions. Research that has focused on the comparison process has noted a marked tendency for performance to be better when participants are required to report a difference between the displays rather than report the absence-of-a-difference (i.e. a sameness). We refer to this performance asymmetry as report-difference superiority (RDS). It has been suggested that RDS reflects the operation of a reflexive mechanism that generates a mismatch signal during the comparison of visual input with information maintained in VSTM. This bottom-up mechanism therefore gives evidence for the presence of a feature change but not for the absence of such a change; consequently a sameness is harder to detect than a difference between two displays (Hyun et al. 2009). We test this explanation, and determine whether by itself it is a sufficient explanation of the RDS. In a delayed comparison task we find the RDS effect is most prevalent when items retain the same display locations, however the effect does persist even when compared item locations were scrambled across memory and test arrays. However, with a conjunction task this scrambling of locations was effective in wholly abolishing the RDS effect. We consider that the RDS effect is a consequence of local comparisons of features, as well as global statistical comparisons.
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Camp SJ, Pilling M, Gellatly A, 'Object substitution masking and its relationship with visual crowding'
Attention, Perception, & Psychophysics 79 (5) (2017) pp.1466-1479
ISSN: 1943-3921AbstractObject substitution masking (OSM) occurs when the perceptibility of a brief target is reduced by a trailing surround mask typically composed of four dots. Camp et al. (Journal of Experimental Psychology: Human Perception and Performance, 41, 940–957, 2015) found that crowding a target by adding adjacent flankers, in addition to OSM, had a more deleterious effect on performance than expected based on the combined individual effects of crowding and masking alone. The current experiments test why OSM and crowding interact in this way. In three experiments, target-flanker distance is manipulated whilst also varying mask duration in a digit identification task. The OSM effect—as indexed by the performance difference between unmasked and masked conditions—had a quadratic function with respect to target-flanker distance. Results suggest it is OSM affecting crowding rather than the converse: Masking seems to amplify crowding at intermediate target-distractor distances at the edge of the crowding interference zone. These results indicate that OSM and crowding share common mechanisms. The effect of OSM is possibly a consequence of changes to the types of feature detectors which are pooled together for target identification when that target must compete for processing with a trailing mask in addition to competition from adjacent flankers.Published here Open Access on RADAR -
Feller S, Gellatly A, 'Obligatory processing of irrelevant gesture'
Gesture 15 (1) (2016) pp.60-78
ISSN: 1568-1475AbstractThis paper presents a study of selected iconic gestures with a view to determining their effects on RT in a task-relevant and a task-irrelevant context. In two experiments, participants were presented with a coloured shape on a computer screen, a spoken statement referring to the presented shape, and a gesture that was task irrelevant. The findings from both experiments show strong support for the assumption that gesture processing is obligatory; irrelevant gestures affected speed of task performance. Furthermore the findings suggest that for slower, more cognitively controlled decisions incongruent gestures have an inhibitory effect, while for faster, more cognitively automated decisions congruent gestures have a facilitatory effect.Published here -
Camp SJ, Pilling M, Argyropoulos I, Gellatly ARH, 'The role of distractors in Object Substitution Masking'
Journal of Experimental Psychology: Human Perception and Performance 41 (4) (2015) pp.940-957
ISSN: 0096-1523AbstractPublished here Open Access on RADARIn object substitution masking (OSM) a surrounding mask (typically comprising of 4 dots) onsets with a target but lingers after offset; under such conditions, the ability to perceive the target can be significantly reduced. OSM was originally claimed to occur only when a target was not the focus of attention, for instance, when embedded in an array of distractors (Di Lollo, Enns, & Rensink, 2000). It was argued that the distractors influenced the time taken for focal attention to reach the target. Some recent work, however, failed to find any such distractor influence; the effect of mask duration was found to be independent of set size when steps were taken to avoid ceiling effects in the smallest set size condition (Argyropoulos, Gellatly, Pilling, & Carter, 2013; Filmer, Mattingley, & Dux, 2014). In 3 experiments, we repeatedly found that set size manipulations can interact with mask duration (in which neither ceiling nor floor effects are evident), with the effect of the mask on target perceptibility being amplified according to the number of distractor items. However, a further experiment (Experiment 4) showed that crowding by nearby distractors was actually responsible for this "set size" effect. When decoupled from crowding, set size alone did not interact with masking, though it did influence overall accuracy. Thus, the presence of distractors does influence OSM, but not in the way originally assumed by Di Lollo and colleagues in their model. The Crowding × OSM interaction suggests that the 2 phenomena involve partly overlapping mechanisms.
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Pilling M, Gellatly A, Argyropoulos Y, Skarratt P, 'Exogenous spatial precuing reliably modulates object processing but not object substitution masking.'
Attention, Perception, & Psychophysics 76 (6) (2014) pp.1560-1576
ISSN: 1943-3921AbstractPublished here Open Access on RADARObject substitution masking (OSM) is used in behavioral and imaging studies to investigate processes associated with the formation of a conscious percept. Reportedly, OSM occurs only when visual attention is diffusely spread over a search display or focused away from the target location. Indeed, the presumed role of spatial attention is central to theoretical accounts of OSM and of visual processing more generally (Di Lollo, Enns, & Rensink, Journal of Experimental Psychology: General 129:481-507, 2000). We report a series of five experiments in which valid spatial precuing is shown to enhance the ability of participants to accurately report a target but, in most cases, without affecting OSM. In only one experiment (Experiment 5) was a significant effect of precuing observed on masking. This is in contrast to the reliable effect shown across all five experiments in which precuing improved overall performance. The results are convergent with recent findings from Argyropoulos, Gellatly, and Pilling (Journal of Experimental Psychology: Human Perception and Performance 39:646-661, 2013), which show that OSM is independent of the number of distractor items in a display. Our results demonstrate that OSM can operate independently of focal attention. Previous claims of the strong interrelationship between OSM and spatial attention are likely to have arisen from ceiling or floor artifacts that restricted measurable performance.
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Skarratt P, Gellatly A, Cole G, Pilling M, Hulleman J, 'Looming motion primes the visuomotor system.'
Journal of Experimental Psychology: Human Perception and Performance 40 (2) (2014) pp.566-579
ISSN: 0096-1523AbstractA wealth of evidence now shows that human and animal observers display greater sensitivity to objects that move toward them than to objects that remain static or move away. Increased sensitivity in humans is often evidenced by reaction times that increase in rank order from looming, to receding, to static targets. However, it is not clear whether the processing advantage enjoyed by looming motion is mediated by the attention system or the motor system. The present study investigated this by first examining whether sensitivity is to looming motion per se or to certain monocular or binocular cues that constitute stereoscopic motion in depth. None of the cues accounted for the looming advantage. A perceptual measure was then used to examine performance with minimal involvement of the motor system. Results showed that looming and receding motion were equivalent in attracting attention, suggesting that the looming advantage is indeed mediated by the motor system. These findings suggest that although motion itself is sufficient for attentional capture, motion direction can prime motor responses.Published here Open Access on RADAR -
Argyropoulos I, Gellatly A, Pilling M, Carter W, 'Set Size and Mask Duration Do Not Interact in Object-Substitution Masking'
Journal of Experimental Psychology: Human Perception and Performance 39 (3) (2013) pp.646-661
ISSN: 0096-1523 eISSN: 1939-1277AbstractObject-substitution masking (OSM) occurs when a mask, such as four dots that surround a brief target item, onsets simultaneously with the target and offsets a short time after the target, rather than simultaneously with it. OSM is a reduction in accuracy of reporting the target with the temporally trailing mask, compared with the simultaneously offsetting mask. It has been thought that. OSM occurs only if attention cannot be rapidly focused, or prefocused, on the target location. One line of evidence for this is a reported interaction between target display set size and the duration of the trailing mask. We analyze the evidence for this interaction and suggest it occurs only as an artifact of data being compressed by a ceiling effect. We report six experiments that support this interpretation by showing that the interaction is always absent unless a ceiling effect is induced. We go on to analyze other evidence to support the notion that attention modulates OSM, and argue that in each case, the data either reflect a ceiling effect or can be explained in another way. Our data and our analyses of the existing literature have strong implications for how OSM should be conceptualized.Published here -
Argyropoulos I, Gellatly A R H, Pilling M, Carter W, 'Set size and mask duration do not interact in object substitution masking'
Journal of Experimental Psychology: Human Perception and Performance 39 (3) (2013) pp.646-661
ISSN: 0096-1523AbstractPublished hereObject-substitution masking (OSM) occurs when a mask, such as four dots that surround a brief target item, onsets simultaneously with the target and offsets a short time after the target, rather than simultaneously with it. OSM is a reduction in accuracy of reporting the target with the temporally trailing mask, compared with the simultaneously offsetting mask. It has been thought that OSM occurs only if attention cannot be rapidly focused, or prefocused, on the target location. One line of evidence for this is a reported interaction between target display set size and the duration of the trailing mask. We analyze the evidence for this interaction and suggest it occurs only as an artifact of data being compressed by a ceiling effect. We report six experiments that support this interpretation by showing that the interaction is always absent unless a ceiling effect is induced. We go on to analyze other evidence to support the notion that attention modulates OSM, and argue that in each case, the data either reflect a ceiling effect or can be explained in another way. Our data and our analyses of the existing literature have strong implications for how OSM should be conceptualized. (PsycINFO Database Record (c) 2012 APA, all rights reserved).
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Pilling M, Gellatly A, 'Task probability and report of feature information: What you know
about what you ‘see’ depends on what you expect to need'
Acta Psychologica 143 (3) (2013) pp.261-268
ISSN: 0001-6918AbstractWe investigated the influence of dimensional set on report of object feature information using an immediate memory probe task. Participants viewed displays containing up to 36 coloured geometric shapes which were presented for several hundred milliseconds before one item was abruptly occluded by a probe. A cue presented simultaneously with the probe instructed participants to report either about the colour or shape of the probe item. A dimensional set towards the colour or shape of the presented items was induced by manipulating task probability — the relative probability with which the two feature dimensions required report. This was done across two participant groups: One group was given trials where there was a higher report probability of colour, the other a higher report probability of shape. Two experiments showed that features were reported most accurately when they were of high task probability, though in both cases the effect was largely driven by the colour dimension. Importantly the task probability effect did not interact with display set size. This is interpreted as tentative evidence that this manipulation influences feature processing in a global manner and at a stage prior to visual short term memory.Published here -
Guest D, Gellatly A, Pilling M, 'Reduced OSM for long duration targets: individuation or items loaded into VSTM?'
Journal of Experimental Psychology: Human Perception and Performance 38 (6) (2012) pp.1541-1553
ISSN: 0096-1523AbstractTypical studies of object substitution masking (OSM) employ a briefly presented search array. The target item is indicated by a cue/mask that surrounds but does not overlap the target and, compared to a common offset control condition, report of the target is reduced when the mask remains present after target offset. Given how little observers are able to report of item arrays that have been presented for several hundred milliseconds (Wolfe, Reinecke, & Brawn, 2006), it might be expected that OSM would also be found if the search array is presented for an extended period before the target is cued by onset of a mask surrounding it. However, Gellatly, Pilling, Carter, and Guest (2010) reported that under these conditions OSM is greatly reduced. This target duration effect could be due to identity information about the search array having been loaded into VSTM during the precue period. Alternatively, it can be understood in terms of target/mask individuation and the object updating account of OSM (Lleras & Moore, 2003). The present article reports three experiments investigating which of these possibilities provides the better explanation of the effect of target duration on OSM. The results support the individuation hypothesis and, thereby, the object updating account of OSM. (PsycINFO Database Record (c) 2012 APA, all rights reserved)Published here -
Guest D, Gellatly A, Pilling M, 'The effect of spatial competition between object-level representations of target and mask on object substitution masking'
Attention, Perception, & Psychophysics 73 (8) (2011) pp.2528-2541
ISSN: 1943-3921AbstractPublished hereOne of the processes determining object substitution masking (OSM) is thought to be the spatial competition between independent object file representations of the target and mask (e.g., Kahan & Lichtman, 2006). In a series of experiments, we further examined how OSM is influenced by this spatial competition by manipulating the overlap between the surfaces created by the modal completion of the target (an outline square with a gap in one of its sides) and the mask (a four-dot mask). The results of these experiments demonstrate that increasing the spatial overlap between the surfaces of the target and mask increases OSM. Importantly, this effect is not caused by the mask interfering with the processing of the target features it overlaps. Overall, the data indicate, consistent with Kahan and Lichtman, that OSM can arise through competition between independent target and mask representations.
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Pilling M, Gellatly A, 'Visual awareness of objects and their colour'
Attention, Perception, & Psychophysics 73 (7) (2011) pp.2026-2043
ISSN: 1943-3921AbstractPublished hereAt any given moment, our awareness of what we 'see' before us seems to be rather limited. If, for instance, a display containing multiple objects is shown (red or green disks), when one object is suddenly covered at random, observers are often little better than chance in reporting about its colour (Wolfe, Reinecke, & Brawn, Visual Cognition, 14, 749-780, 2006). We tested whether, when object attributes (such as colour) are unknown, observers still retain any knowledge of the presence of that object at a display location. Experiments 1-3 involved a task requiring two-alternative (yes/no) responses about the presence or absence of a colour- defined object at a probed location. On this task, if participants knew about the presence of an object at a location, responses indicated that they also knew about its colour. A fourth experiment presented the same displays but required a three-alternative response. This task did result in a data pattern consistent with participants' knowing more about the locations of objects within a display than about their individual colours. However, this location advantage, while highly significant, was rather small in magnitude. Results are compared with those of Huang (Journal of Vision, 10(10, Art. 24), 1-17, 2010), who also reported an advantage for object locations, but under quite different task conditions.
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Luiga I, Gellatly A, Bachmann T, 'Delayed offset of distracters masks a local target'
Acta Psychologica 134 (3) (2010) pp.344-352
ISSN: 0001-6918AbstractPublished hereObject substitution masking (OSM) is observed when a brief target surrounded with a mask is presented among distracter stimuli and cannot be identified when it and the distracters disappear but the mask remains in view. We probed whether OSM also occurs without a local mask object when the distracters remain after target offset. We also varied the congruence between the local target and the global search display and the grouping properties of the delayed offset distracters. A target was briefly presented in a global object configuration of distracters that had delayed offset. Results showed that OSM could be observed with delayed offset of distracters grouped into a global mask shape. Congruence of the shapes of the global and local objects did not affect OSM, suggesting that a generalized abstract visual pattern representation of the global object may not be involved in OSM nor did the grouping properties of the delayed offset distracters influence OSM.
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Gellatly A, Pilling M, Carter W, Guest D, 'How does target duration affect object substitution masking?'
Journal of Experimental Psychology: Human Perception and Performance 36 (5) (2010) pp.1267-1279
ISSN: 0096-1523AbstractObject substitution masking (OSM) is typically studied using a brief search display. The target item may be indicated by a cue/mask surrounding but not overlapping it. Report of the target is reduced when mask offset trails target offset rather than being simultaneous with it. We report 5 experiments investigating whether OSM can be obtained if the search display is on view for a period of up to 830 ms but cueing of the target location is delayed. The question of interest is whether OSM must reflect the initial response of the visual system to target onset or whether it can arise in other ways, possibly during the transition from a pre-attentive representation of the target item to an attentional representation of it. Our results show that OSM decreases in strength as target duration increases. An explanation is suggested in terms of the object individuation hypothesis (Lleras & Moore, 2003).Published here -
Pilling M, Gellatly A, 'Object substitution masking and the object updating hypothesis'
Psychonomic Bulletin & Review 17 (5) (2010) pp.737-742
ISSN: 1069-9384AbstractPublished hereThe object updating hypothesis of object substitution masking proposes that the phenomenon arises when the visual system fails to individuate target and mask at the level of object token representations. This hypothesis is tested in two experiments using modifications of the dot mask paradigm developed by Lleras and Moore (2003). Target-”mask individuation is manipulated by the presentation of additional display items that influence the linking apparent motion seen between a target and a spatially separated mask (Experiment 1), and by the use of placeholders that maintain the target object" s presence during mask presentation (Experiment 2). Results in both cases are consistent with the updating hypothesis in showing significantly reduced masking when the conditions promoted target-”mask individuation. However, in both experiments, some masking was still present under conditions of individuation, an effect we attribute to attentional capture by the mask.
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Skarratt P A, Cole G G, Gellatly A, 'Prioritization of looming and receding objects: equal slopes, different intercepts '
Attention, Perception, & Psychophysics 71 (4) (2009) pp.964-970
ISSN: 1943-3921AbstractFranconeri and Simons (2003) reported that simulated looming objects (marked by a size increase) captured attention, whereas simulated receding objects (marked by a size decrease) did not. This finding has been challenged with the demonstration that receding objects can capture attention when they move in three-dimensional depth. In the present study, we compared the effects of objects that either loomed or receded in depth. The results of two experiments showed that whereas both motion types benefited from attentional prioritization, as judged by their search slopes, looming objects elicited shorter response times (RTs). We conclude that both motion types attract attention during search; however, the RT advantage for looming motion seems to reflect a processing enhancement that occurs outside of selection and is conferred on the basis of motion direction.Published here -
Pilling M, Gellatly A, 'Target visibility in the standing wave illusion: Is mask-target shape similarity important?'
Perception 38 (1) (2009) pp.5-16
ISSN: 0301-0066AbstractPublished hereThe perceptibility of a flickering central bar can be dramatically reduced by the presence of two flanking bars presented in counterphase. This phenomenon, known as the 'standing wave illusion', has been suggested to involve local edge interactions (Macknik et al, 2000 Proceedings of the National Academy of Sciences of the USA 97 7556 - 7560). High-level re-entrant mechanisms have also been implicated. Enns (2002, Psychonomic Bulletin & Review 9 489-496) reports an association between the reported viability of the centre bar and its similarity in shape with the flanking bars. We find that this relationship between shape similarity and reported visibility seems to be contingent on the degree of experienced apparent motion. When target duration is shortened, so reducing apparent motion, reports of visibility reflect the amount of abutting contour. In a further experiment we find that luminance discriminations of the centre bar are related to the amount of abutting contour not to shape similarity. This is despite experiment 3 being conducted at stimulus durations for which experiment 2 visibility ratings indicated that shape similarity is important and contour is not. We suggest that this perceived motion may be the factor mediating shape 'effects' in the reported visibility task. We propose that the absence of such shape effects in the discrimination task may be because the task provides an objective measure of visibility that is immune to bias from perceived motion. We also speculate that while target luminance information may be immune to masking resulting from perceived motion, it may be subject to masking due to lateral inhibition.
Other publications
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Gellatly A, Pilling M, 'Object Substitution Masking of Long Duration Targets-now You Don't See It, Now You Do', (2011)
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Gellatly A, Pilling M, 'Visual Awareness of Objects, Their Colour and Orientation', (2011)
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Gellatly A, Pilling M, 'How Does the Duration of Target Presentation Affect Object Substitution Masking?', (2009)
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Gellatly A, Pilling M, 'Object Substitution Masking With a Single Peripheral Dot: Evidence of Object Updating Or Attentional Capture?', (2009)
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Gellatly A, Pilling M, 'Target-mask Spatial Separation Influences the Extent of Object Substitution Masking', (2009)
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Gellatly A, Pilling M, 'When and Why Does Masking Affect Long Duration Targets?', (2009)
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Skarratt PA, Cole GG, Gellatly ARH, 'Inferring Attentional Capture By Differences in Search Slopes', (2008)
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Cole GG, Skarratt PA, Gellatly ARH, 'Is Inhibition of Return Blind?', (2008)