Presentation on theme: "1 PSYC54 Lecture on Jan. 18, 2005: Part I Color and Motion in Shape-from-shadow Pictures Humera Iqbal, John Kennedy, Juan Bai, & Tom Nolis Please note:"— Presentation transcript:
1 PSYC54 Lecture on Jan. 18, 2005: Part I Color and Motion in Shape-from-shadow Pictures Humera Iqbal, John Kennedy, Juan Bai, & Tom Nolis Please note: Other PSYC54 Lecture notes, including those for Jan. 25 (Chapter III), can be found on In the table, click ‘Chapter X – Notes,’ X meaning the number of the chapter. The chapter contents are on https://tspace.library.utoronto.ca/handle/1807/1021
2 Tom Nolis’s Colored Shape-from-shadow Study Apparent luminance may not be the same as physical luminance, somehow affecting our performance in shape-from-shadow perception. This may be especially true if the shadowed region is in one color (e.g., green), and the line at the shadow border is in another (e.g., red). –As another example, a blue line may be perceived as darker than a yellow shadow even though they have the same luminance scores in the software creating the image, and shape-from-shadow perception may be diminished.
Tactile Pictures Juan Bai & John Kennedy PSYC54 Lecture on Jan. 18, 2005: Part II Rationale: Surfaces and edges are tangible as well as visible, hence outline drawings should be possible for the blindfolded sighted people as well as the blind, including the congenitally blind. (Tactile pictures, or haptic pictures, are also called raised-line drawings.)
4 D’Angiulli, Kennedy, & Heller (1998) Participants: –blind children aged 8-13 –blindfolded sighted children, same age group Materials: –eight tactile pictures of common objects
5 D’Angiulli et al.’s (1998) Procedure On trial 1: The children identified the 8 tactile pictures one by one. On trial 2: They identified the same pictures, but in different orders.
6 D’Angiulli et al.’s (1998) Accuracy Results Trial 1 Trial 2 Blind children 46% 56% Blindfolded sighted children 9% 28%
7 Why Accuracy of at Most 56%? The perceiver may find information about figure- ground relations, orientation, occlusion, the observer’s vantage point, and three dimensionality in tactile pictures very difficult to appreciate (Eriksson, 1998). Cup or Turtle?
8 D’Angiulli et al.’s (1998) Important Findings The children often knew where to correct themselves on trial 2: –The sighted children repeated 95% of the correct suggestions and only 3% of the incorrect ones. –The blind repeated 100% versus 24%. They did so without any feedback.
9 Kennedy and Bai’s (2002) Proposal The children in D’Angiulli et al. (1998) might have a criterion to judge how well their suggestions matched the shapes in the pictures, and to decide whether to stay with them. Kennedy and Bai (2002) called this criterion “fit.”
10 What is “Fit?” Fit is the degree of correspondence between the suggested name and the –shapes –proportions, and –orders of the parts in the picture.
11 Reasoning about Fit If most lines are apt for the suggested name, a person may give a high fit, and is more likely to stay with this name.. On average, correct names for tactile pictures should have higher fit with the pictures than incorrect names. Otherwise, the person may give a low fit, and is more likely to change the name.
12 Reasoning about Fit (Cont’d) Relatively high fit: Ss. are most likely to stay with the name on a later trial. Relatively low fit: Ss. are most likely to change the name to another candidate on a later trial. Fit for the names that stay should be higher than fit for the names that are changed.
13 Kennedy and Bai (2002) Exp. 1 Stimuli New (trial 2 only): car, sailboat Old/repeated (trials 1 and 2): fork, hammer, key, person, scissors, swan, toothbrush, umbrella Demonstration (optic and haptic): star Practice (haptic): tree
14 Exp. 1 Procedure Twelve blindfolded sighted university students named 8 tactile pictures, each within 2 minutes. After a break, they named the same pictures again and judged fit, but in different orders and mixed with 2 new pictures. They gave fit judgments for these suggestions, using a 7-point scale (1 means a very low fit, 7 a perfect fit).
15 Exp. 1 Results on Accuracy Accuracy of the 8 suggestions on trial 1: 61% Accuracy of the 8 suggestions on trial 2: 69% (71% for all 10, including ‘old’ and ‘new’).
16 Larger Dimension Means Higher Accuracy Rate The largest dimension of the pictures in K and B (2002) was 22.5 cm (accuracy > 60%): - 50% bigger than Lederman et al. (1990) (accuracy up to 33%). - 30% bigger than D’Angiulli et al. (1998) (accuracy up to 56%).
17 Exp. 1 Results on Accuracy and Fit On trial 1, mean fit for the correct names: 5.6 (on the 7-point scale). mean fit for the incorrect names: 3.6 (p < 0.001).
18 Exp. 1 Results on Accuracy and Fit (Cont’d) On trial 2, for the 8 old pictures, mean fit for the correct names: 5.8; mean fit for the incorrect names: 3.8 (p < 0.001). On trial 2, for all 10 pictures, mean fit for the correct names: 5.8; mean fit for the incorrect names: 3.7 (p < 0.001).
19 Exp. 1 Results on Repetition and Fit Names that stayed on trial 2 had a mean fit of 5.3 on trial 1. Names that were changed on trial 2 had a mean fit of 2.9 on trial 1 (p < 0.02).
20 Exp. 1 Conclusions Correct names had higher fit scores than incorrect names. So fit judgments can predict accuracy for identification of tactile pictures. Names with lower fit judgments were more likely to be changed than names with higher fit judgments. So fit might be the criteria the participates used to decide whether to stay with previous responses.
21 Exp. 2 Rationale High-fit pictures might be remembered as a single chunk, efficiently, since details did not have to be memorized separately. It is likely that the more parts of the display corresponded to the suggested referent, the more it is accessible in our memory task. So higher fit judgments should be coupled with better memory of tactile pictures. Ill-fitting pictures might have extra parts that presented difficulty in recognition memory.
22 Exp. 2 Stimuli New (trial 2 only): star, triangle, car (turned 90-degree clockwise), house (turned 90- degree counterclockwise), coat hanger and pine tree (inverted). Old/repeated (trials 1 and 2): cup, sailboat, table, telephone, plus the 8 stimuli used in Exp. 1 (all inverted on trial 2). Demonstration (optic and haptic): apple Practice (haptic): tree
23 Exp. 2 Procedure Twelve blindfolded Ss. (= subjects) saw tactile pictures twice, the 2nd time mixed with new, distraction pictures. On trial 2 they were asked whether they saw each tactile picture on trial 1. To increase the difficulty of the task: - twelve pictures on trial 1, 6 more on trial 2; - time allowed was 90s on trial 1, 45s on trial 2; - trial 2 introduced various orientations.
24 Pictures successfully remembered as ‘old’ had a mean fit of 5.4 on trial 1. Pictures failed to be recognized as ‘old’ had a mean fit of 2.5 on trial 1. (p < 0.001). Therefore, fit can predict performance on recognition memory for tactile pictures. Exp. 2 Results and Conclusion
25 Exp. 3 Procedure and Findings Another group of 12 blindfolded Ss. assessed fit of the suggestions offered by matched Exp. 1 Ss. Results = mean Pearson correlation coefficient of the 12 pairs of Ss. was 0.6; all r’s were positive (p <.0001, two-tailed binomial). - Six of the r’s reached significant level beyond p =.05.
26 Exp. 3 Conclusions Touch is consistent across participants. Fit judgment is based on physical correspondence between lines and possible referents. It is an objective matter.
27 Exp. 4 Procedure Still another group of blindfolded Ss. each touched 2 pictures and judged fit for their names offered by matched Exp. 1 Ss. (These 2 pictures received the highest/lowest fit scores in Exp. 1.) Then, they gave confidence rating on a 7-point scale for their fit judgments (1 low, 7 high).
28 Exp. 4 Findings The difference between fit judgments for the 2 pictures per participant was 3.0, twice that of the difference between the confidence judgments, p <.007. This is because both high and low fit judgments received high confidence scores, with mean confidence of 6.4 for high fit judgments (M = 6.6), and mean confidence of 4.9 for low fit judgments (M = 3.6).
29 Exp. 4 Conclusions Fit judgments cannot be substituted by confidence judgments. Even low fit judgments can be coupled with relatively high confidence judgments, since poor fit is based on assessment of the correspondence between the physical features of the picture and the physical features of a suggested identity.
30 Exp. 5 Procedure and Findings A group of Ss. visually judged fit for the names offered by matched Exp. 1 Ss. Therefore, touch and vision extract the same information from outlines. Results = fit judgments of the 2 groups (visual and tactual group) were positively correlated.
31 Overall Conclusions D’Angiulli et al.’s (1998) study indicated that Ss. have a accurate and consistent standard to judge their identification of tactile pictures. K and B’s (2002) experiments supported the idea that the basis for this standard is fit, which is the physical correspondence between the picture and its suggested name. Fit judgments of tactile pictures are related usefully to identification accuracy, repetition, remembering, confidence, and visual judgments.
32 Blind People and Outline Drawings Lines copying surface edges give us surface edge impressions, including lines in tactile pictures. Drawings identified by blind children (Kennedy, 1993)
33 Kennedy et al.’s (1972) study on Tactile Pictures Kennedy, Fox, and O’Grady’s (1972) raised-line drawings included four imprints and four projections
34 The stimuli were 8 tactile pictures measured about 10 cm by 7 cm. Kennedy et al.’s (1972) Study Thirty-four sighted Harvard students were asked to identify the pictures, firstly by touch (i.e., blindfolded), then by vision. Results = haptically identified 2.4 of the 8, the easiest being the hand, the hardest being man with crossed arms and man with arm up (one identification for each).
35 Kennedy et al.’s (1972) Study (Cont’d) A group of 8 blind Harvard students (5 congenitally blind) tried to identify the same 8 pictures by touch. On average the blind identified 1.25 pictures. - easiest: hand (three times), fork, & cup. Eight blind volunteers in Toronto, mostly teens, touched each picture for 2 minutes. On average they identified 1.75 pictures. - easiest: hand, fork, & face (three for each).
36 Implications from Kennedy et al. (1972) Errors made by the blind do not appear to be random, but make visual sense. - e.g., the table was called by the Toronto blind volunteers a house (twice); the fork was called a tree (twice), a brush, an ice-cream cone, etc. There is some practical ability with pictures in the blind. On the other hand, the 10-20% accuracy rate calls for improvement. Perhaps providing a suitable context will do?
37 References D’Angiulli, A., Kennedy, J. M., & Heller, M. A. (1998). Blind children recognizing tactile pictures respond like sighted children given guidance in exploration. Scandinavian Journal of Psychology, 39, Eriksson, Y. (1988). Tactile Pictures: Pictorial Representations for the Blind Gothenburg: Gothenburg University Press. Kennedy, J. M. (1993). Drawing and the Blind. New Haven, CT: Yale University Press. Kennedy, J. M., & Bai, J. (2002). Haptic pictures: Fit judgments predict identification, recognition memory, and confidence. Perception, 31(8), Kennedy, J. M., Fox, N., & O’Grady, K. (1972). Can ‘haptic pictures help the blind see? Harvard Graduate School of Education Bulletin, 16, Lederman, S. J., Klatzky, R. L., Chataway, C., & Summers, C (1990). Visual mediation and the haptic recognition of two-dimensional pictures of common objects. Perception and Psychophysics, 47,