Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Posner’s Cueing Task

Evaluation of Attention & Spatial Cueing based on
Posner Paradigm (Posner Cueing Task)
...
Nagaraju (201550822)
Venkata RaghuRam (200401090)
International Institute of Information Technology, Hyderabad
...
Formulated by Michael Posner, the task assesses an individual’s ability
to perform an attentional shift
...

Accordingly, this report is devoted to discussion of the results of experiments in human
spatial attention and a comparison of them with same approaches as Posner performed in
1980
...
In addition, studies of
human performance may help investigators of neural systems toward the needed integration of
their studies of separate anatomical structures
...


INTRODUCTION
Posner's spatial cueing task has been used to measure manual and eye-movement reaction
times to target stimuli in order to investigate the effects of covert orienting of attention in
response to different cue conditions
...

They are instructed to fixate at a central point on the screen, marked by a dot or cross
...
For a brief period, a cue is presented on the screen
...
The observer must respond to the target immediately after detecting it
...
Following a set inter-trial
interval, lasting usually between 2500 and 5000 ms, the entire paradigm is repeated for a set
number of trials predetermined by the experimenter
...

CUES:
Two major cue types are used to analyze attention based on the type of visual input
...
It is an arrow or other directional cue pointing to the left or right box on the screen
...
An exogenous cue is presented outside of
the center of focus, usually highlighting the left or right box presented on the screen
...
This cue relies on visual input from the peripheral
visual field (Peripheral vision is a part of vision that occurs outside the very center of gaze
...
"Far peripheral" vision refers to the area at the edges of the visual field, "mid-peripheral"
vision exists in the middle of the visual field, and "near-peripheral", sometimes referred to as
"para-central" vision, exists adjacent to the center of gaze)
...
In valid trials, the stimulus
is presented in the area as indicated by the cue
...
Conversely, in
invalid trials, the stimulus is presented on the side opposite to that indicated by the cue
...
Posner used a ratio of 80% valid trials and 20% invalid trials in
his original studies
...
Some trials do not present cues prior to presenting the target
...
Some tasks use neutral trials that do present cues
...
For example, a neutral cue could be a doublesided arrow
...
Since the participant is not allowed to move their eyes in response to the cue, but
remain fixated on the centre of the screen, differences in reaction time between target stimuli
preceded by these three cue conditions indicates that covert orienting of attention has been
employed
...
This method is used to differentiate overt and covert
attention
...
Covert attention involves mental focus and attention to an
object without significant eye movement, and is the predominant area of interest when using the
Posner cueing task for research
...
The ratio makes it beneficial for a participant to covertly shift

attention towards the cued location, as it would be an accurate predictor for the majority of the
time, giving rise to quicker target detection and response
...
This results
in decreased reaction times in Posner's spatial cueing task for validly cued targets, and slower
reaction times in response to invalidly cued targets: “Detection latencies are reduced when
subjects receive a cue that indicates where in the visual field the signal will occur” (Posner,
Snyder & Davidson, 1980)
...
They also result in more intense
processing of stimuli, and increase the probability of an individual detecting a near-threshold
event occurring in the periphery (such as a slight lighting up of a box in the periphery, that may
not have been noticed had attention been elsewhere)
...
Previous studies using this spatial cueing task found that in
addition to cue validity, behavioural reactions were also affected by SOA
...


MOTIVATION
During the last few years of research on human cognition, there has grown up a number of
similar views of how the human nervous system is organized in the performance of speciesspecific human behaviour such as reading (LaBerge and Samuels, 1974; Posner, 1978)
...
Although some
have argued that a skills approach is antithetical to the study of internal attentional mechanisms
(Neisser, 1976), most work on skill has also assumed, with Bartlett, the importance of
mechanisms of limited capacity (Broadbent, 1977)
...
Accordingly, this paper is devoted to discussion of the results of experiments in human
spatial attention and a comparison of them with Posner cueing task
...
In addition, studies of human performance may help
investigators of neural systems toward the needed integration of their studies of separate
anatomical structures
...
Details regarding stimuli
Posner's cueing task has been used to measure manual and eye-movement reaction times to
target stimuli in order to investigate the effects of covert orienting of attention in response to
different cue conditions
...
All stimuli will be presented on a 15
...
During
each trial a small white fixation plus sign will continuously be presented in the centre of the
screen
...
Number of selected experiments
The experiment will have 2 tasks: Endogenous & Exogenous cueing task
...
An endogenous cue is presented in
the centre of the screen, usually at the same location as the centre of focus
...
This cue relies on input from the
central visual field
...
An endogenous cue can also be an
object or image in the periphery, a number of degrees away from the centre, but still within the
visual angle
...

In brief; Participants will be presented with a plus sign detection task driven by an
exogenous/endogenous spatial cue
...
After 750 ms, a cue will appear in one of
the two square for 100, 200, or 500 ms in randomized order, followed by a highlighting one of
the two squares, in the same (valid trial) or in the opposite (invalid trial) position as the cue
...
No
...

4
...
A 5 min break was
provided after 100 trails to the participants
...
Difference in design with respect to original paper
A) The original paper uses EOG to monitor the eye movements however we are interested in
only learning that the cue orients visual attention, which enhances processing at that cued
(attended) location
...
When the resources are allocated
at the cued location, a performance benefit at the attended location arises
...

6
...

7
...
Linear Regression Analysis:

Linear regression is an approach for modelling the relationship between a scalar dependent
variable y and one or more explanatory variables X
...

2
...
T-tests are very useful because they usually perform well in the face of
minor to moderate departures from normality of the underlying group distributions
...

The Software that were used are: MATLAB 2015a, PsychoToolBox & Opensesame Plugin
...
01
...
It is most
often used when comparing statistical models that have been fitted to a data set, in order to
identify the model that best fits the population from which the data were sampled
...


Mean Reaction Time (RT) and Accuracy across trials
RTs(ms)
Trial

Accuracy (%)

Valid

Exogenous Cue
Endogenous Cue

Invalid

Valid

Invalid

1198
...
70

99
...
12

988
...
32

90
...
23

RT Experiment:
The results from the RT experiment were similar with the reported by Posner in 1980
...
378 ms), F(1,12) = 24
...
1, d = 0
...


Figure 1: Cue-Stimulus Time (msec
...
) for different cues
...
This
difference was reliable for the incorrect trials (321 ms vs
...
39, p <
...
61,
and marginally reliable for the correct trials (325 ms vs
...
13, p <
...
52
...
In short,
instructions to be fast and accurate are not equivalent to instructions to be as accurate as possible
...


Figure from Posner’s
reported results
...
Error bars
represent 95% CI for within subject design
...
r
...
ISI
520
500
480
460
440
420
400
380
0-200

200-400

Cue-target ISI Valid

400-600
Cue-target ISI Invalid

600-800

800-1000

Cue-target ISI Neutral

Figure 3: ISI Responses for Valid, Invalid & Neutral trials
In trials with short cue-target ISIs (0–200 ms), subjects were faster in both the valid and
invalid condition
...
This crossover effect is significant for ISIs
between 400 and 600 ms with responses to targets after valid and neutral cues being on
average 13 ms slower than responses to targets at uncued locations
...


CONCLUSIONS
Our findings match up with Posner’s experiment as: Spatial attention is not completely reliant on
conscious visual input & Detection latencies are reduced when subjects receive a cue that
indicates where in the visual field the signal will occur
...
Also, with
long cue-target ISIs, responses to targets are slower when they occur at the cued location
irrespective of the cued feature
...
However, in otherwise identical experiments with noninformative cues, there was no effect in accuracy but substantial effects in parallel RT
experiments
...
Posner, M
...
(1980)
...
The Quarterly journal of experimental
psychology 32 (1): 3–25
...
Posner M I, Snyder C R, Davidson B J (1980)
...

Journal of Experimental Psychology, 109(2):160-174
...
Posner M I, Nissen M J, Ogden W C (1978)
...


DISTRIBUTION OF WORK DONE
1
...

c) Collection of data
d) Analysis of data
...
C
...
RaghuRam
a) Preparing Design Document
b) Collection of data



---