Lina I Davitt - Academia.edu (original) (raw)
Papers by Lina I Davitt
This thesis reports the results of five novel studies that used eye movement patterns to elucidat... more This thesis reports the results of five novel studies that used eye movement patterns to elucidate the role of shape information content of object shape representation in human visual perception. In Experiments 1, and 2 eye movements were recorded while observers either actively memorised or passively viewed different sets of novel objects, and during a subsequent recognition memory task. ..• -'", ••. Fixation data were contrasted against different models of shape mralyses based on surface curvature bounding vs. internal contour and low level image visual saliency. The results showed a preference for fixation at regions of internal local features (either concave or/and convex) during both active memorisation and passive viewing of object shape. This pattern changed during the recognition phase where there was a fixation preference towards regions containing concave surface curvature minima. It is proposed that the preference of fixation at regions of concavity reflect the o...
This study used eye movement patterns to examine how high-level shape information is used during ... more This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision.
This study examines the kinds of shape features that mediate basic- and subordinate-level object ... more This study examines the kinds of shape features that mediate basic- and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic- and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic- than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic- and subordinate-level classification are mediated by object representation...
This thesis reports the results of five novel studies that used eye movement patterns to elucidat... more This thesis reports the results of five novel studies that used eye movement patterns to elucidate the role of shape information content of object shape representation in human visual perception. In Experiments 1, and 2 eye movements were recorded while observers either actively memorised or passively viewed different sets of novel objects, and during a subsequent recognition memory task. Fixation data were contrasted against different models of shape analyses based on surface curvature bounding vs. internal contour and low level image visual saliency. The results showed a preference for fixation at regions of internal local features (either concave or/and convex) during both active memorisation and passive viewing of object shape. This pattern changed during the recognition phase where there was a fixation preference towards regions containing concave surface curvature minima. It is proposed that the preference of fixation at regions of concavity reflect the operation of a depth-se...
One fundamental aspect of understanding appearance is the visual perception of shape, and how thi... more One fundamental aspect of understanding appearance is the visual perception of shape, and how this is modulated by task demands. Here we examined how eye movement patterns relate to the perception of shape during tasks of object recognition and the planning of prehensile movement. Participants carried out either a recognition task (where they learned a set of novel objects and were then tested on recognition), or were asked to plan a reaching movement. The results show that eye movement patterns were linked to the perception of shape, and that these patterns varied between tasks: not only in terms of fixation and saccade parameters but also scan patterns.
Journal of Vision, 2012
This study used eye movement patterns to examine how high-level shape information is used during ... more This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision.
Acknowledgements This research was supported by an award from the Responsible Gambling Trust (RGT... more Acknowledgements This research was supported by an award from the Responsible Gambling Trust (RGT) to R. D. Rogers and E. C. Leek. The authors would like to thank Marc Etches for his support and flexibility during the completion of the project, the operator administrators for facilitating contacts with LBO customers, and the shop managers for their patience during study visits, and, of course, the customers themselves for taking part. Finally, we thank Chris Wilkinson and the game-developers at S-G Gaming for their technical advice.
Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in P... more Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in Psychology (PeePs) is a free summary of ongoing research trends common to six APA View in browser WHAT DO WE SEE WHEN WE SEE SHAPE? A remarkable aspect of human vision is our ability to recognize familiar objects across variations in size, viewpoint, and lighting. Moreover, people can recognize objects at different levels of classification: An object might be identified as a vehicle, a car, or a Honda Civic. However, little is known about the contribution of basic image-based features (e.g., curvature) as opposed to semantic features (e.g., wheels) in these visual recognition processes.
One fundamental aspect of understanding appearance is the visual perception of shape, and how thi... more One fundamental aspect of understanding appearance is the visual perception of shape, and how this is modulated by task demands. Here we examined how eye movement patterns relate to the perception of shape during tasks of object recognition and the planning of prehensile movement. Participants carried out either a recognition task (where they learned a set of novel objects and were then tested on recognition), or were asked to plan a reaching movement. The results show that eye movement patterns were linked to the perception of shape, and that these patterns varied between tasks: not only in terms of saccade parameters but also scan patterns.
Vision Research, 2015
This study investigated whether, and under what conditions, stored shape representations mediatin... more This study investigated whether, and under what conditions, stored shape representations mediating recognition encode extrinsic object properties of sensory input that vary according to viewing conditions. This was examined in relation to cast shadow. Observers (N=90) first memorised a subset of 3D multi-part novel objects from a limited range of viewpoints rendered with either no shadow, object internal shadow, or both object internal and external (ground) plane shadow. During a subsequent test phase previously memorised targets were discriminated from visually similar distractors across learned and novel views following brief presentation of a same-shape masked prime. The primes contained either matching or mismatching shadow rendering from the training condition. The results showed a recognition advantage for objects memorised with object internal shadow. In addition, objects encoded with internal shadow were primed more strongly by matching internal shadow primes, than by same shape primes with either no shadow or both object internal and external (ground) shadow. This pattern of priming effects generalised to previously unseen views of targets rendered with object internal shadow. The results suggest that the object recognition system contains a level of stored representation at which shape and extrinsic properties of sensory input can be conjointly encoded. Here, this is shown by the conjoint encoding of shape and object internal shadow. We propose that this occurs when cast shadow cannot be discounted during perception on the basis of external cues to the scene lighting model.
The Quarterly Journal of Experimental Psychology, 2015
Current theories of object recognition in human vision make different predictions about whether t... more Current theories of object recognition in human vision make different predictions about whether the recognition of complex, multipart objects should be influenced by shape information about surface depth orientation and curvature derived from stereo disparity. We examined this issue in five experiments using a recognition memory paradigm in which observers ( N = 134) memorized and then discriminated sets of 3D novel objects at trained and untrained viewpoints under either mono or stereo viewing conditions. In order to explore the conditions under which stereo-defined shape information contributes to object recognition we systematically varied the difficulty of view generalization by increasing the angular disparity between trained and untrained views. In one series of experiments, objects were presented from either previously trained views or untrained views rotated (15°, 30°, or 60°) along the same plane. In separate experiments we examined whether view generalization effects inter...
The Quarterly Journal of Experimental Psychology, 2009
The "hybrid" model of object recognition (Hummel, 2001) propose... more The "hybrid" model of object recognition (Hummel, 2001) proposes that unattended objects are processed holistically, while attended objects are processed both holistically and analytically. Supporting evidence for this claim was reported by Thoma, Hummel, and Davidoff (2004) who showed that, unlike whole object primes, unattended split object parts (presumed to require analytic processing) do not elicit repetition priming. Here we tested the generality of this finding by contrasting priming for whole and part prime stimuli as a function of prime informativeness and by modifying the design so that both unattended whole and part prime displays contained a single perceptual object. Unlike Thoma et al. (2004) the results showed negative (rather than an absence of) priming for unattended half object primes. These findings place new constraints on theoretical models of the role of attention in object recognition.
Journal of Experimental Psychology: Human Perception and Performance, 2014
This study examines the kinds of shape features that mediate basic-and subordinate-level object r... more This study examines the kinds of shape features that mediate basic-and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic-and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic-than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic-and subordinate-level classification are mediated by object representations. These representations make explicit internal part boundaries, and distinguish concave and convex regions of bounding contour. The classification task constrains how shape information in these representations is used, consistent with the hypothesis that both parts-based, and image-based, operations support object recognition in human vision.
PsycEXTRA Dataset, 2000
Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in P... more Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in Psychology (PeePs) is a free summary of ongoing research trends common to six APA View in browser WHAT DO WE SEE WHEN WE SEE SHAPE? A remarkable aspect of human vision is our ability to recognize familiar objects across variations in size, viewpoint, and lighting. Moreover, people can recognize objects at different levels of classification: An object might be identified as a vehicle, a car, or a Honda Civic. However, little is known about the contribution of basic image-based features (e.g., curvature) as opposed to semantic features (e.g., wheels) in these visual recognition processes.
This thesis reports the results of five novel studies that used eye movement patterns to elucidat... more This thesis reports the results of five novel studies that used eye movement patterns to elucidate the role of shape information content of object shape representation in human visual perception. In Experiments 1, and 2 eye movements were recorded while observers either actively memorised or passively viewed different sets of novel objects, and during a subsequent recognition memory task. ..• -'", ••. Fixation data were contrasted against different models of shape mralyses based on surface curvature bounding vs. internal contour and low level image visual saliency. The results showed a preference for fixation at regions of internal local features (either concave or/and convex) during both active memorisation and passive viewing of object shape. This pattern changed during the recognition phase where there was a fixation preference towards regions containing concave surface curvature minima. It is proposed that the preference of fixation at regions of concavity reflect the o...
This study used eye movement patterns to examine how high-level shape information is used during ... more This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision.
This study examines the kinds of shape features that mediate basic- and subordinate-level object ... more This study examines the kinds of shape features that mediate basic- and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic- and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic- than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic- and subordinate-level classification are mediated by object representation...
This thesis reports the results of five novel studies that used eye movement patterns to elucidat... more This thesis reports the results of five novel studies that used eye movement patterns to elucidate the role of shape information content of object shape representation in human visual perception. In Experiments 1, and 2 eye movements were recorded while observers either actively memorised or passively viewed different sets of novel objects, and during a subsequent recognition memory task. Fixation data were contrasted against different models of shape analyses based on surface curvature bounding vs. internal contour and low level image visual saliency. The results showed a preference for fixation at regions of internal local features (either concave or/and convex) during both active memorisation and passive viewing of object shape. This pattern changed during the recognition phase where there was a fixation preference towards regions containing concave surface curvature minima. It is proposed that the preference of fixation at regions of concavity reflect the operation of a depth-se...
One fundamental aspect of understanding appearance is the visual perception of shape, and how thi... more One fundamental aspect of understanding appearance is the visual perception of shape, and how this is modulated by task demands. Here we examined how eye movement patterns relate to the perception of shape during tasks of object recognition and the planning of prehensile movement. Participants carried out either a recognition task (where they learned a set of novel objects and were then tested on recognition), or were asked to plan a reaching movement. The results show that eye movement patterns were linked to the perception of shape, and that these patterns varied between tasks: not only in terms of fixation and saccade parameters but also scan patterns.
Journal of Vision, 2012
This study used eye movement patterns to examine how high-level shape information is used during ... more This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision.
Acknowledgements This research was supported by an award from the Responsible Gambling Trust (RGT... more Acknowledgements This research was supported by an award from the Responsible Gambling Trust (RGT) to R. D. Rogers and E. C. Leek. The authors would like to thank Marc Etches for his support and flexibility during the completion of the project, the operator administrators for facilitating contacts with LBO customers, and the shop managers for their patience during study visits, and, of course, the customers themselves for taking part. Finally, we thank Chris Wilkinson and the game-developers at S-G Gaming for their technical advice.
Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in P... more Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in Psychology (PeePs) is a free summary of ongoing research trends common to six APA View in browser WHAT DO WE SEE WHEN WE SEE SHAPE? A remarkable aspect of human vision is our ability to recognize familiar objects across variations in size, viewpoint, and lighting. Moreover, people can recognize objects at different levels of classification: An object might be identified as a vehicle, a car, or a Honda Civic. However, little is known about the contribution of basic image-based features (e.g., curvature) as opposed to semantic features (e.g., wheels) in these visual recognition processes.
One fundamental aspect of understanding appearance is the visual perception of shape, and how thi... more One fundamental aspect of understanding appearance is the visual perception of shape, and how this is modulated by task demands. Here we examined how eye movement patterns relate to the perception of shape during tasks of object recognition and the planning of prehensile movement. Participants carried out either a recognition task (where they learned a set of novel objects and were then tested on recognition), or were asked to plan a reaching movement. The results show that eye movement patterns were linked to the perception of shape, and that these patterns varied between tasks: not only in terms of saccade parameters but also scan patterns.
Vision Research, 2015
This study investigated whether, and under what conditions, stored shape representations mediatin... more This study investigated whether, and under what conditions, stored shape representations mediating recognition encode extrinsic object properties of sensory input that vary according to viewing conditions. This was examined in relation to cast shadow. Observers (N=90) first memorised a subset of 3D multi-part novel objects from a limited range of viewpoints rendered with either no shadow, object internal shadow, or both object internal and external (ground) plane shadow. During a subsequent test phase previously memorised targets were discriminated from visually similar distractors across learned and novel views following brief presentation of a same-shape masked prime. The primes contained either matching or mismatching shadow rendering from the training condition. The results showed a recognition advantage for objects memorised with object internal shadow. In addition, objects encoded with internal shadow were primed more strongly by matching internal shadow primes, than by same shape primes with either no shadow or both object internal and external (ground) shadow. This pattern of priming effects generalised to previously unseen views of targets rendered with object internal shadow. The results suggest that the object recognition system contains a level of stored representation at which shape and extrinsic properties of sensory input can be conjointly encoded. Here, this is shown by the conjoint encoding of shape and object internal shadow. We propose that this occurs when cast shadow cannot be discounted during perception on the basis of external cues to the scene lighting model.
The Quarterly Journal of Experimental Psychology, 2015
Current theories of object recognition in human vision make different predictions about whether t... more Current theories of object recognition in human vision make different predictions about whether the recognition of complex, multipart objects should be influenced by shape information about surface depth orientation and curvature derived from stereo disparity. We examined this issue in five experiments using a recognition memory paradigm in which observers ( N = 134) memorized and then discriminated sets of 3D novel objects at trained and untrained viewpoints under either mono or stereo viewing conditions. In order to explore the conditions under which stereo-defined shape information contributes to object recognition we systematically varied the difficulty of view generalization by increasing the angular disparity between trained and untrained views. In one series of experiments, objects were presented from either previously trained views or untrained views rotated (15°, 30°, or 60°) along the same plane. In separate experiments we examined whether view generalization effects inter...
The Quarterly Journal of Experimental Psychology, 2009
The "hybrid" model of object recognition (Hummel, 2001) propose... more The "hybrid" model of object recognition (Hummel, 2001) proposes that unattended objects are processed holistically, while attended objects are processed both holistically and analytically. Supporting evidence for this claim was reported by Thoma, Hummel, and Davidoff (2004) who showed that, unlike whole object primes, unattended split object parts (presumed to require analytic processing) do not elicit repetition priming. Here we tested the generality of this finding by contrasting priming for whole and part prime stimuli as a function of prime informativeness and by modifying the design so that both unattended whole and part prime displays contained a single perceptual object. Unlike Thoma et al. (2004) the results showed negative (rather than an absence of) priming for unattended half object primes. These findings place new constraints on theoretical models of the role of attention in object recognition.
Journal of Experimental Psychology: Human Perception and Performance, 2014
This study examines the kinds of shape features that mediate basic-and subordinate-level object r... more This study examines the kinds of shape features that mediate basic-and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic-and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic-than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic-and subordinate-level classification are mediated by object representations. These representations make explicit internal part boundaries, and distinguish concave and convex regions of bounding contour. The classification task constrains how shape information in these representations is used, consistent with the hypothesis that both parts-based, and image-based, operations support object recognition in human vision.
PsycEXTRA Dataset, 2000
Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in P... more Issue 17-March 13, 2014 Click Below for Tables of Contents Particularly Exciting Experiments in Psychology (PeePs) is a free summary of ongoing research trends common to six APA View in browser WHAT DO WE SEE WHEN WE SEE SHAPE? A remarkable aspect of human vision is our ability to recognize familiar objects across variations in size, viewpoint, and lighting. Moreover, people can recognize objects at different levels of classification: An object might be identified as a vehicle, a car, or a Honda Civic. However, little is known about the contribution of basic image-based features (e.g., curvature) as opposed to semantic features (e.g., wheels) in these visual recognition processes.