Discussion centered around the difference between psychophysical and psychological experiments, the role of the preceding saccade and inertia, and whether pupil motion is an eye movement that should be measured or an eye tracker should measure eye ball rotation only.

Last Friday, most of the eye-tracking group were at SWAET (http://eyelab.se/swaet/), our local variety of ECEM. Highlights include the method keynote, the keynotes by Daniel Richardsson, and Zoi Kapoula and several really good talks on mental imagery, educational psychology, medical imaging and other uses of eye tracking. The conference ended with a panel discussion around the initiative to standardize the measurements of data quality, where manufacturers and researchers met and there was much agreement that standardization would benefit both the researcher community and manufacturers.

Next Friday, the ET seminar will discuss an experiment proposal by our guest Marlit Schmidt. The entire program for the eye tracking seminar can be found at http://wiki.humlab.lu.se/dokuwiki/doku.php?id=public:eyetracking_seminar

Nothing could be more wrong, and the sooner you understand that, the more likely that your eye tracker study will be a success. Eye movement data must be interpreted against several sciences of its own: First, the vision science, which tells us how perception is structured, with effects such as object crowding, which allows you to see detail in the periphery when there is not much visual crowding around it. This has direct implication of the sizes of your AOIs, and for the discussion of your paper. Vision science is full of useful knowledge like this, that matter for any eye movement study.

Second, you often need to know about the neurology of eye movements when you analyze data. If you have a sequence of short fixations and long saccades, for instance, it is evidence of prioritized activity in a particular stream in the brain. Knowledge about the neurology behind your result will have implications for the theoretical conclusions you can draw.

Thirdly, you need to know about the psychology of eye movements. Memory processes are associated with several eye movement paradigms. Individual difference exist for many of the measures we can draw from an eye tracker. And attention in particular is a tricky concept that does not align perfectly with the line of gaze. Know about these and other psychological processes, and your eye tracking study will be better, irrespective of application area.

If you treat the eye tracker as just a tool, and decide to ignore the accompanying theory, it will be more difficult to publish your study. Reviewers are likely to protest, as they should.

In the current eye tracking group we have worked hard to build a cross-disciplinary competence that covers many of the sciences of eye tracking. If you are serious about eye tracking, come and meet us!

Alexander Eitel is also helpful in preparing for the large digital classroom that the eye tracking group is setting up to study learning in classroom contexts.

Finally, we celebrated Jana Holsanovas birthday. Jana played an important role in founding the eye-tracking group in 1995, thus indirectly the whole Humanities Laboratory. In the mid 90′s, she made advanced studies of the translation between pictures and speech at the same time as the first psycholinguistics studies experimented with similar methods  in what would become the `visual world paradigm’. She has since made a multitude of studies of newspaper reading and mental imagery and will now be a leading researcher in the upcoming digital classroom project.

Next week, the vast majority of the eye tracking group goes to Stockholm, where we will give 10 talks at the Scandinavian Conference of Applied Eye Tracking, including the initial lecture on eye-tracking methodology by myself.

The next ET-seminar will be on the 11th of May, when we discuss a paper by Marcus, Ignace and myself about what happens at the end of saccades, and perhaps also how this opens up the questions what an eye tracker is. The full seminar list can be found at http://wiki.humlab.lu.se/dokuwiki/doku.php?id=public:eyetracking_seminar

Today’s seminar in the eye-tracking group focussed on educational psychology. Alexander Eitel is a guest in our long-standing collaboration with Tübingen on educational psychology and eye movements, and is here to write up his thesis. On April 27th, he presents the last paper of the thesis on this seminar. It addresses the question whether picture content seen for very short period is helpful in understanding a text, and also relates to mental imagery and memory. Marlit Schmidt from Kiel investigates how people answer multiple-choice questions, and is currently planning her eye-tracking study. Our discussion concerned cued retrospective protocols as a means to investigate strategies used in selecting between alternatives that are more or less related. On May 18th, a full seminar will be devoted to this issue of psychometrics.

We also planned our activities at the SWAET conference (http://www.eyelab.se/swaet/).

Next week, we have three events in the eye-tracking group:

1) Fiona Mulvey presents her eye-movement study on Williams patients (at the Neuropsychology seminar); Wednesday April 19 at 12.15-13.00

2) Zenzi Griffin from Austin talks her research on speech production using eye tracking; Wednesday April 19 at 15.15-17.00

3) Richard Andersson defends his thesis; Friday April 20 at 13.15-…

The full program with all details of the eye tracking seminar can be found at http://wiki.humlab.lu.se/dokuwiki/doku.php?id=public:eyetracking_seminar.

MONDAY March 19th————————————————————

9.00 Introduction and welcome. Who we are and what this course is about (Kenneth Holmqvist)

9.15 Eye movement research – some examples of application areas (Kenneth Holmqvist)

10.00 The visual system and eye movements (Fiona Mulvey)

10.45 Break

11.15 Hardware (Kenneth Holmqvist)

12.00 Lunch

13.00 On-stage demo with one remote eye tracker, and lecture on how practically to work with the eye-tracker (Halszka Jarodzska and others)

14.00 Hands-on GROUP A

15.20 Hands-on GROUP B

TUESDAY March 20th————————————————————

9.00 A single study from vague idea to publication; the case of mental imagery (Kenneth Holmqvist)

10.00 From raw data to fixations and saccades (Linnea Larsson)

10.45 Break

11.00 Eye-tracking in the educational sciences (Halszka Jarodzka)

12.00 Lunch

13.00 Cognitive eye-tracking measures and subjective cognitive states (Fiona Mulvey)

14.00 Hands-on GROUP C

15.20 Hands-on GROUP D

A number of reading stimuli are being planned, including the Moses illusion, antonym resolution, and standardized news items with comprehension questions. Participant specific data that are likely to influence behavior, e.g. prefrontal control over eye-movemnts in anti-saccade data, extroversion/introversion tests (EPQR) will be used.

Discussion focussed on comparability between nature and traffic sounds: Are peaks and rhythms the same in both conditions? Alexander played one example sound of each, which were very similar. Does these two sounds allow for generalizations? Are the differences so small that no differences will be seen in the eye movement data? Should participants be told which sound is which? Would synchronization between sound and eye movements be clearer if text scrolled through a small box at which the reader gazes?

Is the reading part important? The anti-saccade task is established, and results are well-known, so why not run a study with the anti-saccade task while participants listen to sounds? Executive control and working memory are much easier to explain than eye movements on text.

We also noted that the deadline for SWAET 2012 in Stockholm (the conference we founded) is March 30th, and all members of the ET-group are encouraged to submit abstracts to it. You can also expect to be asked to review submissions.

Finally we debated the upcoming ECEM conference (in Lund August 2013), and our discussions with the international eye-tracking community about how to innovate it.

In next week’s seminar, we will read the position paper from our international committee for standardization of data quality in eye trackers. The full seminar is available at http://wiki.humlab.lu.se/dokuwiki/doku.php?id=public:eyetracking_seminar

In R, 500 pairs of samples were created consisting of 15 values each. The mean value of the first sample was set to approximately 10, that of the second sample to 11. The standard deviations of both samples were approximately 1 each, and the correlation between the samples varied around zero. The R-script can be downloaded here.

The graph shows the results. The correlation between the samples is shown on the X-axis, and on the Y-axis the difference between the p-values of the two t-tests (p-independent minus p-paired). Values above the horizontal zero line (positive differences) indicate that p-independent was larger than p-paired. Values below the zero line indicate (negative differences) that p-paired was larger than p-independent. The color of the dots indicate which of the two tests ‘won’, that is one test was significant while the other one was not (p < .05). The independent samples t-test ‘won’ 23 times (green dots), whereas the paired samples t-test ‘won’ 12 times (purple dots).

The graph shows that the results of the contest depend on the degree of correlation between the samples. The paired-samples t-test only wins at positive correlations, whereas the independent-samples t-test only wins at negative correlations. Interestingly, the turn-point is not exactly at r = 0, but seems to be shifted somewhat to the right, at approximately r = 0.05. The relation between the correlation coefficient and the result of the contest is related to the fact that the paired-samples t-test is really a single-sample t-test over difference scores. A more positive correlation reduces the variance of the difference scores and consequently makes the paired t-value larger in favor of the independent-samples t.