The Extent to Which Retinal Images Can Be Perceived - Lab Report Example

Extent to which retinal images can be perceived [Name and course details here] Abstract Many studies have been done to find the difference between actual and perceived objects. These studies have measured for constancy of shape, distance, size, tilt and texture. These experiments sought to show that the human brain has a compensation mechanism by which objects are viewed as relatively the same irrespective of the observer’s relative motion and position. Researchers have also shown that together with this compensation the observer is sometimes able to see the uncorrected retinal image. Coren, et al.(1979) demonstrated this by the drawing of a blind person drawing from haptic feed back and compared it to a child’s drawing before the child had learnt the rules of perspective. This shows that there is a part of the retinal image that is seen but not consciously acknowledged. This experiment will seek to delve deeper into that part of visual perception. Extent to which retinal images can be perceived In the human eye the image of a viewed object is first formed on the retina, upside down. The image is then passed through different pathways to rectify it or process it into a more comprehensible form. During growth and development of human beings the human mind develops different mechanisms of presenting a consistent and comprehensible image. The consistently changing angle of view and movement of objects viewed, lighting and distance at which they are viewed means the retina receives a different image with changes as slight as a tilt of the head. This apparent correction for objects viewed at distance, and tilted is called shape constancy. The degree of correction to create constancy varies correspondingly with distance and angle of view. There is a relationship between size, distance and angle of view and correction for constancy Kofek (1935). Gillam (20000) Posits that objects viewed at closer distances have less correction as opposed to objects viewed at longer distances. This is because objects at close range are more familiar they would need less correction. This correction happens in the frontal plane part of the brain. Once an image leaves the Retina it is sent to the frontal plane where it is corrected to give the perceived image. When observers are asked to draw an image of the object the observe they tend to draw an image more akin to the actual image than to that formed in the frontal plane (). This phenomenon is called regression to the real (Thouless, 1939). This is more evidently observed when children are asked to draw an object they view and when blind people are asked to draw from haptic feedback (Kennedy, 1980). This research shall conduct experiments to find the extent to which we can observe the actual image (the retinal image) over the frontal plane image. The experiment shall also try to see how the perception of retinal image varies with distance. It will seek to verify the idea that objects at longer distances suffer more distortion from the actual object so the observer will be able to see more of the retinal image. Method Design This experiment had judged shape ratio as the independent variable. This was measured for a circle viewed at three different distances with the observer’s head at a fixed height. The observer then picked an ellipsis that most closely matched their perception of the circle viewed at an oblique angle. Material and procedure The participants observed a circle on a table and with their heads at a fixed height. The participants were then shown different ellipses on cards from directly above. This is because an ellipsis viewed at an angle would be displayed obliquely would cause more correction in the frontal plane. This would then not give an accurate measure for judged shape ratios as intended. The cards had ellipses of varying diameter so that there was different judged shape ratios. The data was then used to calculate a mean judged ratio, retinal ratio and Brunswick ratio. The Brunswick ratio calculated had the lowest being zero and the highest being one. A Brunswick ratio of zero showed that there was no difference between the perceived image and the retinal image and that of one means there was no similarity between the retinal image and the judged image. The data collected was all fed into a computer and all computations were done using a data mining and analysis software. In this case SPSS. Hypotheses It is hypothesized that this result will serve to corroborate findings of those dicussed above and show that: There is a significant and measureable extent to which an individual judges a viewed object and an object’s perception is not entirely that formed in the frontal plane. That observers will see less of the retinal image at close distances as opposed to retinal image formed from objects observed at longer distance. Results Results were taken at three different distances: 25cm, 65cm and 105cm. This then had three variables calculated judged ratio, retinal ratio and Brunswick ratio. These were calculated for all 167 participants. Table 1 Computed results for observations at 25cm M SD n JR 0.94 0.08 166 RR 0.83 0.14 166 JR-RR 0.12 0.19 166 BR 0.59 0.59 166 From the above table it is can be seen that at a 25cm viewing distance the 166 (n=166, 100%) respondents returned a Judgment Ratio measure of (M=0.94, SD=0.08). The Brunswick ration was also measured at (M=0.59, SD=0.59) for all 166 participants (n=166, 100%). Table 2 Computed results for observations at 65cm M SD n JR 0.84 0.10 166 RR 0.55 0.11 166 JR-RR 0.28 0.16 166 BR 0.59 0.35 166 From the above table it is can be seen that at a 65cm viewing distance the 166 (n=166, 100%) respondents returned a Judgment Ratio measure of (M=0.84, SD=0.10). The Brunswick ration was also measured at (M=0.59, SD=0.35) for all 166 participants (n=166, 100%). Table 3 Computed results for observations at 105cm M SD n JR 0.74 0.16 166 RR 0.39 0.11 166 JR-RR 0.35 0.19 166 BR 0.56 0.25 166 From the above table it is can be seen that at a 65cm viewing distance the 166 (n=166, 100%) respondents returned a Judgment Ratio measure of (M=0.74, SD=0.16). The Brunswick ration was also measured at (M=0.56, SD=0.25) for all 166 participants (n=166, 100%). Table 4 Result pairs T df Sig. 2tail Pair 1 RR_25 - RR_65 27.58 166 Read More