Motivation and Challenges

There has been much debate around perception of subliminal cues, and their effect on human behavior, especially whether such an effect indeed exists or is only a false marketing myth (e.g., James Vicary, 1957). The idea that awareness can influence cognition is not new – Peirce and Jastrow reported in 1884 that people can perceive small differences in pressure to the skin without conscious awareness of different sensations. Moreover, it is well known that certain subliminal cues can facilitate certain behaviors. For example, store chains spray fragrances with a subtle influence outside their stores to attract customers, background music in shopping malls is said to increase sales by subliminally stimulating shoppers.

Potential of Subliminal Perception

As the prevention of additional cognitive workload in human-computer interfaces is a topic of increasing importance, new forms or modalities of interaction between humans and interfaces need to be explored. One promising approach is to use subliminal stimulation or the "injection" of information below aware perception; however, it is still an open question whether subliminal communication through non-conscious processing actually works. Recent empirical research suggests the assumption that subliminal interaction techniques improve human-computer interaction by reducing workload undertaken by sensory channels, but another group of experimental researchers has found that it does not, or even cannot, work.

In order to resolve this controversy, it would be a great opportunity to discuss with experts in the field how they have tested subliminal interaction, and to what conclusions they have come. A possible result of the workshop would be a general statement whether or not subliminal techniques can be used to deliver information to the user without adding workload, or in what specific constellation, setting, channels, etc. the approach works.Elementary questions such as the following need to be carefully taken under consideration in this field of research.

  1. How good is the mind at extracting meaning from stimuli of which one is not consciously aware?
  2. How can we measure the (positive or negative) effects of subliminal information cues?
  3. How would something presented subliminally persuade a person if he or she did not consciously attend to it? (as it is generally accepted that such stimuli are weak and often presented at very low intensity)

Topics of Interest

Potential topics to be covered in position papers and discussed at the workshop include, but are not limited to

  • Philosophy or rationale for the use of subliminal interfaces in UbiComp environments,
  • Ethical issues in application of subliminal perception and impact to HCI,
  • Risk assessment in subliminal interfaces (from the view of the user, the system developer),
  • Evaluation methodologies for the perception of subliminal information (qualitative, quantitative validations),
  • Subliminally delivered information and its relation with other constructs - cognitive load - perceived performance - emotions, etc.,
  • Characteristics of subliminally delivered information (e.g., reachable bandwidth, natural bounds, complexity of information, speed of perception, appropriate modalities, strength/ duration/frequency),
  • Effectiveness of subliminal perception in UbiComp Environments (e.g., context-aware adaptive interfaces, user-aware adaptive interfaces (fatigue, emotion detection), personalized commercials),
  • Modalities
    1. visual perception (flashing picture, video, text, etc.),
    2. auditory perception (compressed speech, music, non-speech sounds, etc.),
    3. haptic/tactile perception,
    4. olfactory or other perception,
  • Issues with subliminal perception
    1. social acceptance or preference,
    2. privacy issues,
    3. security issues
  • Individual differences in threshold of subliminal perception (age, gender, (dis)abilities, cognitive style, cultural/ethnologic background, etc.)