METHOD TO EVALUATE PSYCHOLOGICAL RESPONSES TO VISUAL OBJECTS

• US 20100010366A1
• Filed: 12/22/2006
• Published: 01/14/2010
• Est. Priority Date: 12/22/2006
• Status: Abandoned Application

• Current Assignee: Neuro-Insight Pty., Ltd.
• Original Assignee: Neuro-Insight Pty., Ltd.
• Inventors: Silberstein, Richard Bernard
• Application Number:
  US12/520,860
• Publication Number:
  US 20100010366A1
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/16 Devices for psychotechnics using teaching or educational appliances G09B1/00 - G09B7/00; Testing reaction times ; Devices for evaluating the psychological state
• CPC Class Codes: A61B 5/161 Flicker fusion testing eye testing A61B3/00
• CPC Class Codes: A61B 5/378 Visual stimuli

Abstract

A method of evaluating the response of a subject to visual features of a visual display, the method including the steps of: (a) presenting a visual display having particular visual features to the subject during a first period; (b) determining brain activity of the subject during the first period; (c) presenting reference display material to a subject during a second period; (d) determining reference brain activity of the subject during the second period; (e) tracking the gaze position of at least one of the eyes of the subject on the visual display during the first period; and (f) evaluating the response of the subject to particular visual features of the visual display by determining differences in brain activity determined between steps (b) and (d) when the gaze of the subject is directed at the particular features.

Claims

1. A method of evaluating the response of a subject to visual features of a visual display, the method including the steps of:

(a) presenting a visual display having particular visual features to the subject during a first period;

(b) determining brain activity of the subject during the first period;

(c) presenting reference display material to a subject during a second period;

(d) determining reference brain activity of the subject during the second period;

(e) tracking the gaze position of at least one of the eyes of the subject on the visual display during the first period; and

(f) evaluating the response of the subject to particular visual features of the visual display by determining differences in brain activity determined between steps (b) and (d) when the gaze of the subject is directed at the particular features.

2. A method as claimed in claim 1 wherein the visual display is printed advertising material, text layout, product design, packaging website, the interior or exterior of a building.

3. A method as claimed in claim 2 wherein the visual display is displayed on a video screen.

4. A method as claimed in claim 3 including the step of selecting the visual features of the visual display and determining the areas where the selected visual features are located on the video screen and wherein step (e) determines when the gaze position of the subject falls upon respective area of the selected visual features on the video screen.

5. A method as claimed in claim 4 wherein the differences in brain activity determined in step (f) are averaged for each selected visual feature.

6. A method as claimed in claim 1 wherein steps (a) to (e) are presented to a plurality of subjects and step (f) includes the steps of averaging the differences in brain activities of the subjects.

7. A method as claimed in claim 1 wherein steps (b) and (d) are carried out by determining gamma or high frequency EEG or MEG activity.

8. A method as claimed in claim 1 wherein steps (b) and (d) are carried out by detecting EEG or MEG activity in the frequency range 8 to 13 Hz.

9. A method as claimed in claim 1 wherein steps (b) and (d) are carried out by assessment of the phase of steady state visually evoked potentials (SSVEP) in EEG signals obtained from the subject or subjects or by assessment of steady state visually evoked responses (SSVER) in MEG signals obtained from the subject or subjects.

10. A method as claimed in claim 1 wherein steps (a) and (c) include the steps of placing electrodes at scalp sites to obtain output EEG signals which enable assessment of:

visual attention to detail of the visual features;

emotional intensity associated with the visual features;

long term memory encoding associated with the visual features;

engagement with the visual features;

attraction associated with the visual features;

desirability associated with the visual features; and

/or

likeability associated with the visual features.

11. A method as claimed in claim 10 including the step of applying a sinusoidally varying visual flicker stimulus to each subject during steps (a) and (c) to thereby enable calculation of Fourier coefficients from said output signals to thereby enable calculation of said SSVEP amplitudes and/or phase differences.

12. A method as claimed in claim 11 wherein said SSVEP amplitude and phase are calculated by the equations:

${\mathrm{SSVEP}}_{\mathrm{amplitude}}=\sqrt{\left(A_n^2+B_n^2\right)}$ ${\mathrm{SSVEP}}_{\mathrm{phase}}=a<br><br><br><br>\tan <br><br>\left(\frac{B_n}{A_n}\right)$

where;

a_n and b_n are cosine and sine Fourier coefficients calculated by the equations;

$a_n=\frac{1}{S<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}}<br><br>\underset{i=0}{\overset{S-1}{\sum <br><br>}}<br><br>f<br><br>\left(\mathrm{nT}+i<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}\right)<br><br>\cos \left(\frac{2<br><br><br><br>\mathrm{\pi <br><br>}}{T}<br><br>\left(\mathrm{nT}+i<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}\right)\right)$ $b_n=\frac{1}{S<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}}<br><br>\underset{i=0}{\overset{S-1}{\sum <br><br>}}<br><br>f<br><br>\left(\mathrm{nT}+i<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}\right)<br><br>\sin \left(\frac{2<br><br><br><br>\mathrm{\pi <br><br>}}{T}<br><br>\left(\mathrm{nT}+i<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\tau <br><br>}\right)\right)$

where;

a_n and b_n are the cosine and sine Fourier coefficients respectively where;

n represents the nth flicker stimulus cycle;

S is the number of samples per flicker stimulus cycle;

Δ

τ

is the time interval between samples;

T is the period of one cycle;

f(nT+iΔ

τ

) is the EEG signal (raw or pre-processed using ICA) obtained from said predetermined scalp sites;

and wherein A_n and B_n are overlapping smoothed Fourier coefficients calculated by using the equation;

$A_n=\underset{i=1}{\overset{i=N}{\sum <br><br>}}<br><br>a_{n+i}/N$ $B_n=\underset{i=1}{\overset{i=N}{\sum <br><br>}}<br><br>b_{n+i}/N$

13. A method as claimed in claim 12 including the steps of:

obtaining EEG signals from a plurality of scalp sites of each subject; and

utilising inverse mapping techniques such as BESA, EMSA or LORETA to produce modified EEG signals which represent activity in deeper regions of the brain of each subject such as the orbito-frontal cortex or the ventro-medial cortex.

14. A method as claimed in claim 12 including the step of averaging the Fourier coefficients A_n and B_n for a selected group of subjects and then calculating the SSVEP amplitudes and SSVEP phase differences for said group of subjects.

15. A method as claimed in claim 11 wherein the flicker signal is applied only to the peripheral vision of each subject.

16. A method as claimed in claim 15 including the steps of directing the flicker signal towards the eyes of each subject via first and second screens and wherein each screen includes an opaque area, and wherein the method further includes the step of positioning the screens to the relative position of each subject such that said opaque areas prevent said flicker signal impinging on the fovea of each eye of each subject.

17. A method as claimed in claim 16 wherein the opacity of each screen decreases as a function of distance from its opaque area so that the intensity of the flicker signal impinging on each retina of each subject decreases in value from the central vision to the peripheral vision.

18. A method as claimed in claim 17 including the step of applying a masking pattern to each screen to define the opacity thereof, the method including the step of applying the pattern in accordance with a masking pattern function which provides zero or low gradients for changes in opacity adjacent to its opaque area and peripheral areas thereof which define parts of the flicker signal impinging on the peripheral vision of each subject.

19. A method as claimed in claim 18 wherein the opaque area of each screen is circular and wherein the masking pattern function is selected to be a Gaussian function, so that the opacity P of the screen is defined by the equation:

$P={\mathrm{<br><br>}}^{-{\left(r-R\right)}^2/G^2}$

where;

r is the radial distance from the centre of the opaque area; and

G is a parameter that determines the rate of fall-off of opacity with radial distance, and wherein when r<

R, P=1.

20. A method as claimed in claim 19 wherein G has a value in the range R/4 and 2R.

21. A method as claimed in claim 12 including the steps of applying an electrode to the scalp of each subject at the O₁ site, calculating SSVEP amplitudes and phase differences from EEG signals from said electrode whereby the output signals indicate each subject'"'"'s visual attention to details of the selected visual features.

22. A method as claimed in claim 13 including the step of utilising inverse mapping determines brain activity in the left cerebral cortex in the vicinity of Brodman'"'"'s area 17 whereby the modified output signals indicate each subject'"'"'s visual attention to details of the selected visual features.

23. A method as claimed in claim 12 including the step of applying an electrode to the scalp of each subject at a site which is approximately equidistant from sites O₂, P₄ and T₆, calculating SSVEP amplitudes and phase differences from EEG signals from said electrode whereby the output signals indicate each subject'"'"'s emotional intensity associated with the selected visual features.

24. A method as claimed in claim 13 wherein the step of utilising inverse mapping determines brain activity in the right cerebral cortex in the vicinity of the right parieto-temporal junction whereby the output signals indicate each subject'"'"'s emotional intensity associated with the selected visual features.

25. A method as claimed in claim 12 including the steps of applying an electrode to the scalp of each subject at the F₃, F₄, F_p1 and F_p2 sites, calculating SSVEP amplitudes and phase differences from EEG signals from said electrodes, calculating values for attraction-repulsion using the equation:

attraction=(a₁*SSVEP phase advance at electrode F₃+a₂*SSVEP phase advance at electrode F_p1−

a₃*SSVEP phase advance at electrode F₄−

a₄*SSVEP phase advance at electrode F_p2)

where a₁=a₂=a₃=a₄=1.0

whereby said values indicate each subject'"'"'s attraction or repulsion towards the selected visual features.

26. A method as claimed in claim 13 wherein the step of utilising inverse mapping determines brain activity in:

the right orbito-frontal cortex in the vicinity of Brodman area 11;

the right dorso-lateral prefrontal cortex in the vicinity of Brodman area 9;

the left orbito frontal cortex in the vicinity of Brodman area 11; and

the left dorso-lateral prefrontal cortex in the vicinity of Brodman area 9; and

calculating a value for attraction-repulsion using the equation;

attraction=(c₁*right orbito-frontal cortex (in vicinity of Brodman area

     11)+c₂*right dorso-lateral prefrontal cortex (in vicinity of Brodman area

     9)+c₃*left orbito frontal cortex (in vicinity of Brodman area

     11)+c₄*left dorso-lateral prefrontal cortex (vicinity of Brodman area

     9))

where c₁=1, c₂=1, c₃=1, c₄=1,

whereby said values indicate each subject'"'"'s attraction or repulsion towards the selected visual features.

27. A method as claimed in claim 12 including the steps of applying electrodes to the scalp of each subject at F₃, F₄, P_p1 and F_p2 sites, calculating SSVEP amplitudes and phase differences from said electrodes, calculating values for engagement in features of the advertisement by a weighted mean SSVEP phase advance at said sites using the equation:

engagement=(b₁*SSVEP phase advance at electrode F₃+b₂*SSVEP phase advance at electrode P_p1+b₃*SSVEP phase advance at electrode F₄+b₄*SSVEP phase advance at Electrode F_p2)

where b₁=0.1, b₂=0.4, b₃=0.1, b₄=0.4,

whereby said values indicate each subject'"'"'s engagement in the selected visual features.

28. A method as claimed in claim 13 wherein the step of utilising inverse mapping determines brain activity in:

the right orbito frontal cortex in the vicinity of Brodman area 11;

the right dorso-lateral prefrontal cortex in the vicinity of Brodman area 9;

the left frontal cortex in the vicinity of Brodman area 11; and

the left dorso-lateral prefrontal cortex in the vicinity of Brodman area 9,

calculating SSVEP amplitudes and phase differences from said modified EEG signals from said electrodes; and

calculating a value for engagement using the equation;

engagement=(d₁*right orbito frontal cortex (in vicinity of Brodman area

     11)+d₂*right dorso-lateral prefrontal cortex (in vicinity of Brodman area

     9)+d₃*left orbito frontal cortex (in vicinity of Brodman area

     11)+d₄*left dorso-lateral prefrontal cortex (in vicinity of Brodman area

     9))

where d₁=0.1, d₂=0.4, d₃=0.1, d₄=0.4,

whereby said values indicate each subject'"'"'s engagement in the selected visual features.

29. A method as claimed in claim 3 wherein step (e) includes:

fitting a headset to the subject or subjects having electrodes therein for determining the brain activities of steps (a) and (c);

tracking movements of an eye of each subject relative to his or her headset to generate eye position signals;

tracking the movements of the head of each subject relative to the video screen to produce head position signals; and

combining said eye position and head position signals to thereby determine the gaze position of each subject relative to a reference point on the video screen.

30. A system for evaluating the response of a subject to visual features of a visual display, the system including:

(a) display means for displaying said visual features to the subject;

(b) means for determining brain activity of the subject at predetermined scalp sites of the subject;

(c) gaze tracking means for determining the gaze position of the subject on said display means;

(d) detecting means for detecting when the gaze position of the subject impinges on selected visual features; and

(e) averaging means for calculating average values of brain activity for each of the selected visual features when the detecting means detects that the gaze position of the subject impinges on the respective selected visual features.