Christina Howard's home page

I am a post doc working for Prof Tom Troscianko and Prof Iain Gilchrist at Bristol University

We are currently working on a human attention and machine learning project, investigating how humans monitor CCTV video. I am also interested in how motion characteristics attract attention in scenes containing moving objects.

Previously (2004 – 2007), I studied for my PhD at Cardiff University, working with Dr Alex Holcombe, Dr Petroc Sumner and Prof. Dylan Jones

2000-2001, I completed an MSc at the University of Surrey, in Environmental Psychology.

1997-2000, I completed an MA degree at Oxford University in Psychology, Philosophy and Physiology.

To how many objects can you attend simultaneously?

The demos below show experiments on attention to the orientations and spatial frequencies of multiple objects. These are only cartoons: in the real experiments, motion was smoother, and spatial resolution was much higher than represented here.

Fixate the centre, and try to continuously keep track of the changing features of all the striped Gabor patches that start out being marked by black circles. In the experiments, observers kept track of either one, two or four of the total of five objects.

At the end of each trial, one of the objects being tracked is queried, and observers have to report what they think was the very last feature value (the last orientation or spatial frequency) of that object before it disappeared. Observers adjust a pair of black markers (in the case of orientation) or a sample Gabor patch (in the case of spatial frequency) to indicate the last feature value, then they get feedback.

The results show a gradual decline in precision with the number of objects monitored: the spread of errors becomes greater from monitoring one to monitoring two objects, and from monitoring two to monitoring four objects.

There is also a perceptual lag: observers report feature states from the past! This is especially true for spatial frequency where the presence of some serial processing is implicated.

Typical trials from Experiments 1 (orientation monitoring) and 2 (spatial frequency monitoring).

Published work

Howard, C. J., Troscianko, T., Gilchrist, I. D. (in preparation). Eye-hand lags during a continuous monitoring task.

Howard, C. J., & Holcombe, A. O. (under review). Changes in direction of motion attract attention.

Howard, C. J., Troscianko, T., Gilchrist, I. D., Behera, A. & Hogg, D. C. Searching for threat: factors determining performance during CCTV monitoring. In D. de Waard, J. Godthelp, F.L. Kooi, and K.A. Brookhuis (Eds.) (2009). Human Factors, Security and Safety (pp. 333 - 339). Maastricht, the Netherlands: Shaker Publishing.

Howard, C. J., & Holcombe, A. O. (2008). Tracking the changing features of multiple objects: Progressively poorer perceptual precision and progressively greater perceptual lag. Vision Research, 48, 1164-1180

Published conference abstracts

Howard, C. J., Gilchrist, I. D., Troscianko, T., Behera, A. & Hogg, D. C. (2009). Monitoring CCTV and watching football: expert-novice differences in the magnitude of a visuo-motor buffer [Abstract]. Journal of Vision , 9(8):416, 416a http://journalofvision.org/9/8/416/, doi:10.1167/9.8.416.

Howard, C. J., Troscianko T., Gilchrist I. D. (2008). Searching for threat: eye movements during CCTV monitoring. Perception 37 ECVP Abstract Supplement, p.108.

Howard, C. J., Sumner, P. (2007). How does attention modulate crowding during spatial cueing and dual-task paradigms? Perception 36 ECVP Abstract Supplement p.128.

Howard, C., & Holcombe, A. O. (2006). Progressively poorer perceptual precision and progressively greater perceptual lag: Tracking the changing features of one, two and four objects [Abstract]. Journal of Vision, 6(6):785, 785a, http://journalofvision.org/6/6/785/, doi:10.1167/6.6.785.

Howard, C. J., Holcombe, A. O. (2005). Limits on continuous monitoring of the features of multiple objects. Perception 34 ECVP Abstract Supplement, p.93.

Other conference abstracts

Howard, C. J., Troscianko, T. & Gilchrist, I. D. (2009). Expertise affects visual-motor lags during continuous sports monitoring. Talk at European Conference on Visual Perception meeting, Southampton.

Howard, C. J., Gilchrist, I. D. Troscianko, T., Behera, A. & Hogg, D. (2008). Continuous manual responses and continuous gaze tracking during closed circuit television (CCTV) monitoring. Talk at European Conference on Visual Perception meeting, Southampton.

Howard, C. J., Gilchrist, I. D. & Troscianko, T. (2008). The view from the sidelines: salience, relevance and eye movement convergence while watching a football match. Poster presented at the Applied Vision Association meeting, Bristol.

Howard, C. J., & Sumner, P. (April 2007). Attentional modulation of crowding: an equivalent noise approach. Poster presented at the Experimental Psychology Society meeting, Cardiff.

Howard, C. J., Troscianko, T., Gilchrist, I. D., Behera, A. & Hogg, D. C. (2009). Searching for threat: eye movements during CCTV monitoring. Talk to Bristol Vision Institute.

Howard, C. J., Holcombe, A. O. & Sumner, P. (2007). Spatially directed attention to the features of objects: precision and contributions from serial processing. Talk to Bristol Vision Institute.

Invited talks

Howard, C. J., & Holcombe, A. O. (2009). Does a ‘bounce’ grab attention? Invited talk at the University of Bradford.

Howard, C. J., & Holcombe, A. O. (2008). Does a ‘bounce’ grab attention? Invited talk at the University of Southampton.

Simultaneous attention to positional (“where”) and non-positional (“what”) features of objects. Invited talk at the Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2006.