“[The] basic visual cues of spatial/location, colour, shape, size and motion cues are tested. Investigations focus on two aspects, 1) Users’ ability to identify separate categories and 2) Users’ ability to differentiate visual cues.”
Moonyati Yatid and Masahiro Takatsuka, in “Understanding Spatial and Non-spatial Cues in Representing Categorical Information.”
Yatid and Takatsuka indicate that visual notifications can be positive (attracting attention for urgent matters) or negative (distractions from more important activities). Their experiments were designed to test which of the five key visual clues (spatial/location, colour, shape, size and motion ) would yield the best user responsiveness and accurate interpretations when presented with visual notifications. They also incorporated multiple categories of information to determine user’s ability to decode more complex sets of visual information.
Their findings clearly indicated that accuracy in user performance in responding to notifications was by shape, location and colour. Size and motion readings were proven to degrade quickly as multiple categories of information were added.
So, if your OSS is issuing notifications to your users, it is suggested that you use shape, colour or location to improve interpreted accuracy.