Neisser, U., Becklen, R. (1975). Selective looking: Attending to visually specified events. Cognitive Psychology, 7, 4, 480-494.
I have to say I find these older papers very interesting. It seems they are written attending to some basic rules only, meaning there is space for humour and “easy-going-ness”. They really make an effort to be light and understandable.
A second note goes to all the methodological effort: WOW. I mean…working in a very sci-fi environment makes it hard to remember those days with no digital cameras and no video editing softwares. The authors really had to work hard both to conceive the procedure as to adjust it to each participant.
So, this is the idea.
After the big hype of selective listening, where after listening to two messages simultaneously, people could only pay attention to one of them, the authors decided to apply the same idea to other modality: the sight.
So they videotaped separately two disparate episodes, and then showed them to the participants in complete overlap.
In a short literature review, the authors pose the possibility of being the distance whichmay cause selection. An interesting idea – and that may be useful for the Head-Up display subject which I may study in the future – is that the distance of both objects may be at different optical distances, and thus selection might be ascribed to differential accomodation of the lens of the eye. Because of this, they decided to keep both episodes at the same distance.
The authors’ main hypothesis was that the subjects would easily be able to follow one episode and ignore the other.
Other questions they wanted to see answered were:
– How difficult (or how easy) is it to follow one episode and ignore another when both are presented at the same optical distance in the same binocular vision field?
– Does the substitution of dichtopic for binocular presentation change the difficulty of the task → (won’t be speaking about this variable)
– Will unusual events be noticed if they are not part of the episode being observed?
– Is it possible to follow two independent episodes at the same time if instructed to do so?
The authors videotaped two episodes: The hand game and the ball game.
On the hand game, the authors were playing and, from time to time, they would make synchronization signals (tapping on the blackboard behind). Everytime the participant saw this, he would have to press a switch with the right hand.
On the ball game, three men were playing basketball, moving irregularly. It also had a synch sign, and the participant pressed a switch with the left hand everytime he saw that one.
In both games there were some odd events: sometimes the hand shook, sometimes the ball disappeared, sometimes the men were substitued gradually by three women. These odd events were never mentioned on the intruction phase.
This was the set-up, using half-silvered mirrors and two TV’s, disposed either to present the images binocularly (both eyes) or dichopticly (one for each eye).
The subjects performed several trials:
Trials 1&2 served as baseline for each episode separately.
Trial 3 two episodes were presented, but the subject was instructed to respond tot the ballgame only.
Trial 4 was like Trial 3, but with the hand game only.
Trials 5&6 the subject has to respond to events on both episodes.
Trials 7 to 10 the subject had to follow one game and ignore the other, again, but using slow episodes (half of the events – 20 instead of 40).
1) In the baseline condition, almost no event was missed.
2) When they had to ignore one of the episodes, the performance slightly decreased.
3) Drastic deteroration of performance when subjects had to monitor both episodes simultaneously (20%-40% of events were missed). Participants declared the task was demaning and impossible.
4) The odd events were rarely noticed.
These results took the authors to question if they were due to peripheral registration, but they immediately put aside that option: eye movements cannot be the principal mechanism of selective attention. In this process, nothing disappears. One event is perceived because the relevant information is being picked up and used; other information is not picked up in the first place, and consequently, not used.
The authors suggest the design of some existing optical systems (in 1975) may lead to eye strain and other problems because the scenes are presented at different distances. It would be interesting if these authors manipulated the distance of each episode as well. I will come back to that, I’m sure it’s already somewhere.
I leave you with a 1999 classic: http://www.youtube.com/watch?v=vJG698U2Mvo
Funny fact: They were inspired by the work of Kolers (1969,1972) who wore a headgear fitted with a half-silvered mirror so that the world ahead of him and the world behind him were simultaneously given to the binocular field of view. He said he could easily switch between both views and while attending to one, the other disappeared.