According to Wolfe, et al.,( 2008) a visual search exercise is normally measured by the length of time the search takes. When only a single feature of the target is different from the distractors, the time spent identifying the target is the same regardless of the number of distractors. This search pattern is parallel search. Some of the factors that would elicit this pattern are (i) luminance (ii) color (iii) Size (iv) curvature (v) motion. Serial search on the other hand is where the observer searches the target serially among the distractors. Here the observer scans through every item serially to identify the presence or absence of the target. In serial search, the number of distractors will determine the time taken. Examples that elicit this pattern are; (i) When the target is identical to the distractors. (ii) target is well hidden within the distractors field (iii) Where there is a single target among numerous distractors (iv) Accuracy is essential (v) target has a combination of features.
Parallel search is easy and straightforward. This is because regardless of the number of distractors it is not time dependent.
Parallel search is easier because it involves scanning through the sample saving time rather than the time consuming serial search.
According to Michelle et al., (2009) crowding primarily occurs in the periphery and always lesser in the central vision. This is because crowding is pronounced when flanks are smaller and less where they are bigger.
Brief explanation of cues
Binocular disparity is the difference in images reaching both eyes. The closer the object is, the greater the binocular disparity.
Occlusion is a depth cue indicating a perceived motion direction of an object in a picture.
Linear perspective is used in drawing and paintings to create an illusion of space and distance by a representation of converging parallel lines.
Texture gradient is the fineness or coarseness of an image’s texture that vary depending on the distance from a camera.
Ariel (atmospheric) perspective is the effect that explains or represent the distance between a physical feature, usually a hill or a water body from the camera.
Shading and lighting is a painting or drawing skill used in two dimensional pictures to bring out depth in images. The brightest part of the images indicate closeness to light.
Elevation( Realtive hight) is a cocept used to topographically represent images in a painting or drawing.
Relative size is a technique used where identical objects are shown in different sizes to show distance, the smaller one is further than the bigger one.
Motion Parallax is a depth cue that result as the camera moves. The closer objects move faster than the further ones.
Monocular depth cues evident in the paintings
Antoine Caron painting portray the following cues:
- Ariel (atmospheric) perspective; the buildings in the background are less saturated in color and they assume the same color as the background
- Relative size; the buildings at the background appear smaller than the ones in the foreground yet they are the same objects.
Clande Lorrain paintings portray:
- Shading and lighting; the sunlight brings out the images clearly
- Ariel (atmospheric) perspective; the contrast between the water and the sky at the background lessens
- Relative size; the boats at the background indicate distance.
Paolo Caliari painting portray:
- Elevation( Relative hight); the birds and the clouds appear to be up above.
- Relative size; the people on top of the pillar are smaller than the ones on the forefront.
The Pablo Picaso painting potray:
- Shading and lighting the depths of the images are shown clearly using this technique.
The Russell Drysdale painting potray:
- Shading and lighting; the painting’s depths are illustrated by light and the shading especially the family on the forefront
- Ariel (atmospheric) perspective; the trees get smaller towards the background.
- Elevation( Realtive hight; the plants are clearly shown under the feet of the family in the forefront.
The M. C. Escher’s painting exhibits shading and lighting used well to define the painting; it gives an illusion of a three dimensional picture. The shading and lighting give the depths and shapes in the painting.
References
Michelle, P., Gilchrist, I., Troscianko, T., lovell, G., & Tolhurst, D. (2009). Crowding effects in central and peripheral vision when viewing natural scenes. A Journal of Vision.
Wolfe, J., Kluender, K., Levi, D., Bartoshuk, L., Herz, R., Klatzky, R., et al. (2008). Sensation & Perception, Second Edition.