Bells Test

Background

The Bells Test is a widely used paper-and-pencil diagnostic tool for visual neglect (aka unilateral spatial neglect) and search strategy. Visual neglect is a common condition after a stroke or brain injury where a patient fails to pay attention to or process stimuli on one side of their visual field.

Martin Albert published "A Simple Test of Visual Neglect" (Albert's Test) in 1973. He placed 40 short, black lines randomly across an unlined sheet of paper and asked patients to cross them out, a testing procedure that has become known as a 'cancellation test'. Albert's simple test was highly successful in finding patients suffering from severe neglect but routinely missed those with mild to moderate brain damage. The Star Cancellation Test, developed by Barbara Wilson and colleagues in 1987, was one successful diagnostic tool to assess more moderate degrees of visual neglect by including a mix of distractor items to the visual display which increased a patient's cognitive load during test taking. The Bells Test, added to the fleet of cancellation tests by Louise Gauthier and colleagues in 1989, further increased the cancellation test's sensitivity as a diagnostic tool for mild to moderate visual neglect by systematically increasing the complexity of the visual display. Specifically, the Bells Test consists of a single page that contains 35 target bells mixed into a field of 280 black silhouette distractors (such as horses, houses, and keys). Under the cover, the page is divided into 7 invisible columns, each precisely containing 5 bells and 40 distractors. This structural distribution allows clinicians to quantify the exact location of omitted targets. Unlike the Star Cancellation Test, the Bells Test does not contain any verbal distractors and may, due to its sheer visual density, lead to a higher degree of cognitive fatigue and frustration for patients.

The Millisecond Bells Test adapts the paper and pencil administration of the task to a computerized environment. The original page is presented in the middle of the screen (Note that the script can be set to run the original page size if needed) and participants are asked to select the bell-targets with the mouse or fingers (on touchscreens). Summary variables include several newer measures suggested by Mauro Manusco and colleagues (2019) that depend on age and level of schooling to varying degrees. To this end the Millisecond Bells Test includes an optional survey of demographic variables. Additionally, the Millisecond Bells Test allows the visualization of the search strategy at task conclusion by highlighting the trail from selected location with a blue line as well as marking each location with a visitation number. Correctly selected locations ('bells') are referenced in green; incorrect locations are referenced in red. A screenshot of the search path is taken automatically for future analyses.

Alternative cancellation tasks to diagnose visual neglect include the aforementioned Star Cancellation Test and the Apples Cancellation Test; the only cancellation test that allows the differential diagnoses of egocentric and allocentric neglect.

Task Procedure

Before working on the actual Bells Test, participants work through a shorter practice phase in which they are asked to locate all the distractor items as well as the bell on a separate demonstration page. The name of each of the 15 items (e.g. apple, bell, saw, tree etc.) appears on screen and participants have to select the item with the mouse of finger (on touchscreens). The order of the presented items is fixed with the bell appearing as the 8th item. After the practice phase, patients receive the instructions to find all the bells that they can within 5 minutes and ignore all other items. Once they press the Start button, the test begins and the test page is presented. Anytime participants select an item via mouse click or touch, a blue circle appears around the selected screen location. When participants are done selecting all the bells, they can press a Submit button. If not all the bells have been found at this point, one single (verbal) reminder is provided that asks "Are you sure that all the bells are now circled?" and allows participants to continue looking for the missing bells if needed. The test is over if the allotted time is up, or if participants submit their responses for the final time.

What it Measures

The Bells Test is a measure of visual neglect and search strategy.

Psychological domains

• Visuospatial Attention: The ability to consciously direct and shift focus across near-extrapersonal space (the area within arm's reach).
• Selective Attention: The capacity to focus strictly on relevant target stimuli (the bells) while actively ignoring irrelevant environmental noise.
• Focused Attention: The mental stamina required to remain locked onto a single, repetitive task over a continuous period without becoming distracted.
• Visual Search and Scanning: The systematic strategy used to look through an environment.

Main Performance Metrics

• Asymmetry Score: Difference of number of bells selected on the left vs. right; measure of Visual Neglect
• Accuracy Score: Analysis of the number of bells not selected; measure of Selective Attention
• Execution Time: Analysis of the execution time of the search; measure of Processing Time

Psychiatric Conditions

The following patient groups are routinely tested with the Bells Test

• Traumatic Brain Injury (TBI)
• Stroke
• Alzheimer’s Disease (AD)
• Parkinson's Disease (PD)
• Brain Tumors or Infections

References

Search Google Scholar for peer-reviewed, published research using the Inquisit Bells Test.

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Gauthier, L., Dehaut, F., & Joanette, Y. (1989). The Bells Test: A quantitative and qualitative test for visual neglect. International Journal of Clinical Neuropsychology, 11(2), 49–54.

de CR, O., de FC, L., CP, K., & PF, R. (2016). Use of Bells Test in the Evaluation of the Hemineglect Post Unilateral Stroke. Journal of Neurology and Neuroscience, 7. https://doi.org/10.21767/2171-6625.1000124

Basagni, B., De Tanti, A., Damora, A., Abbruzzese, L., Varalta, V., Antonucci, G., Bickerton, W. L., Smania, N., & Mancuso, M. (2017). The assessment of hemineglect syndrome with cancellation tasks: a comparison between the Bells test and the Apples test. Neurological Sciences, 38(12), 2171–2176.

Wong, C. E. I., Cotrena, L. D. B. C., Joanette, Y., & Fonseca, R. P. (2017). Reliability and construct validity of the bells test. Avaliação Psicologica, 17(1), 28–. https://doi.org/10.15689/ap.2017.1701.04.13128

Mancuso et al (2019). A New Standardization of the Bells Test: An Italian Multi-Center Normative Study. Front. Psychol. 9:2745.