week 2 Flashcards
(18 cards)
Dichotic listening tasks
presenting two messages to different ears and seeing which break into conscious attention
We filter out information in the unattended ear based on pitch and more
Separate abilities
learning about these things separately reflects traditional broad categories of study within the field
Two phenomena that helps us do this with attention and perception are inattentional blindness and change
Dichotic viewing
In the 70s and 80s researchers tried to create a visual analogue of dichotic listening
the aim was to better understand how attention was related to how we viewed our worlds
Neisser 1979
Documented a wide range of experiments to make a visual version of dichotic listening
Generally involved two videos shown over each other (through an elaborate set up with mirrors)
Participants had a task that oriented them to the display (e.g. count the hand slaps, how many times they passed the ball etc).
An unexpected event (or events) then occurred
If it was in the unattended video then it was generally missed
Of 28 participants only 6 noticed
Simons & Chabris (1999)
They actually investigated:
Visual similarity (how similar the unexpected event is to the task);
Task difficulty (how many attentional resources are needed);
Medium (superimposed vs. ‘live’); and
The nature of the event (umbrella woman vs. gorilla)
Participants watched videos of two teams (of three people) passing basketballs
The players were either in white shirts, or black shirts
The unexpected event was varied: woman with umbrella; woman in gorilla suit
Lab conditions
Whilst the findings with ‘real world’ stimuli are striking it is worth noting they also built on the work of Mack & Rock (1998)
They demonstrated inattentional blindness under controlled lab conditions
This is important to rule out a host of alternative explanations in scenarios where lots varies
Mack & Rock (1998)
Series of experiments reported in a book
Typical paradigm involves fixating on the centre of a cross (approx. 200ms) and deciding which of the two arms of it are longer
On the 3rd or 4th trial an unexpected object is shown (e.g. a coloured shape) within a quadrant of the cross
Then complete another trial where they still have to make the judgement but know something might appear
Followed by a final trial in which they just have to see what appears
When presented in this way approx. 25% of observers miss the object in the critical trial but can see it with full attention
They also tried putting the unexpected event in the middle (fixation point) and the cross off to the side
In these trials 60-70% missed the unexpected event! Even though it was where they were asked to fix their eyes at the start of each trial
Attention needed
Attention appears to be essential for perceiving;
When your attention is focused on another task you will miss unexpected events; and
This is particularly true for those that are dissimilar to the items in the task you are focusing on
Limitation
In practical terms investigating inattentional blindness can be very challenging
Given that expectations affect the result, there is only ever one critical trial and therefore one data point
Inattentional blindness tasks are therefore very fast but require a lot of participants!
They also rely on self-report, so conclusions are limited to ‘within conscious awareness’.
Change blindness
Change blindness = the failure to notice a change in a visual scene
Change blindness is thought to require at least the following stages:
Focused attention on the relevant location
Encoding in memory the information in this location before the change
Encoding in memory the information in this location after the change
Comparing the two representations
Consciously detecting the difference between the memory and the visual experience
Rensink et al. (1997)
To investigate change blindness Rensink et al. (1997) developed a task known as the flicker task
Designed to investigate change blindness in natural scenes
The tasks are known as flicker tasks because of the strange flickering effect caused by inserting the blank screen between images
This is similar to eye blinks and cuts in scenes in films…
If it wasn’t there people could detect the change because of the movement (or motion signals) from the scene
The blank screen in-between creates a global change, which masks any small changes
This ensures that responses are based on the ability of the observer to detect changes based on the visual information alone, not motion signals
Rensink et al. (1997) part 2
Performance was then measured as how many alternations were needed to notice the change
Without the flickering the average was around 1.4 alternations (circa. 0.9 seconds)
With the flickering the average was around 7-17 alternations, but some participants required 80!
Whether the change was of central interest or marginal interest was important
Changes in marginal interest took a lot longer to be identified (17 alternations on average)
Than those of central interest (7 alternations on average
Even when the ‘size’ of the change was roughly equal
Attention is therefore key to explaining why people are able to ‘look at’ but still not ‘see’ visual changes around them
In ‘normal’ conditions motion cues are usually available to us and we seem to rely on them to detect change (but can be missed with a blink or a saccade)
When removed, and left with just the visual information it is surprising just how bad we are at detecting change
IB vs. CB
Both therefore differ in several important ways:
Inattentional blindness is affected by expectations, but change blindness isn’t
Inattentional blindness requires observers to be engaged in a demanding primary task (divided attention) but change blindness doesn’t
Change blindness involves memory processes as well as attention and perception, but inattentional blindness does not
Real-world applications
The most relevant circumstances for cognitive blindnesses are those in which missing something in our visual world can have significant consequences
Driving and Change Blindness
When it comes to driving accidents there is ‘Failing to look’ but crucially also ‘Looking but failing to see’ (Staughton & Storie, 1977)
One possibility is that of driving without attention (i.e. in automatic pilot; Kerr, 1991)
However, it is also possible that, even when attentive, changes in the environment could be missed
Galpin et al. (2009)
Extended these phenomena to road scenes
Varied location and semantic relevance (i.e. relevance to driving)
Semantic relevance was important, but it seemed to interact with location
Curiously, changes with no semantic relevance that were central to the view were noticed least often
But driver experience was not important (despite being predicted to be)
Eyewitness Testimony and Inattentional Blindness
Witnesses to crimes don’t always know that they are about to witness one
They may be attending to something else in the environment at the time (e.g. a phone, their own thoughts, etc)
This can lead them to miss crucial details but without an awareness that they might have missed something
