Exam%3%'%1%of%7%Final Exam PS 217, Fall 2010 1. Farzin, et al. (2010) wrote an article that appeared in Psychological Science titled: “Spatial resolution of conscious visual perception in infants.” The abstract read: Humans’ conscious awareness of objects in their visual periphery is limited. This limit is not entirely the result of reduced visual acuity. Rather, it is primarily caused by crowding—the difficulty identifying an object when it is surrounded by clutter. The effect of crowding on visual awareness in infants has yet to be explored. Do infants, for example, have a fine-grained “spotlight,” as adults do, or do infants have a diffuse “lantern” that sets limits on what they can register in their visual periphery? We designed an eye-tracking paradigm to psychophysically measure crowding in infants between 6 months and 15 months of age. We showed infants pairs of faces at three eccentricities, in the presence or absence of flankers, and recorded infants’ first saccade from central fixation to either face. Infants could discriminate faces in the periphery, and flankers impaired this ability. We found that the effective spatial resolution of infants’ visual perception increased with age, but was only half that of adults. For our purposes, the two conditions were Age (6-, 9-, 12-, and 15-month olds) and Crowding (b = uncrowded and c = crowded). To simplify one of their studies and place it in a format that is consistent with your knowledge, let’s imagine the study as a 2x4 independent groups design. Half of the two hundred and forty participants (60 6-month-olds, 60 9-month-olds, 60 12-month-olds, and 60 15-month-olds) viewed the Mooney faces as either Uncrowded or Crowded (so 30 6-month-olds saw Uncrowded and 30 saw Crowded, etc.). The dependent variable is the mean threshold of eccentricity (departure from center, so greater eccentricity is more peripheral) for detecting the face as upright or upside down. Thus, higher eccentricity for thresholds indicates that the infants could detect the upright face (for example) at a greater eccentricity (more peripheral presentation). Complete the source table below and interpret the results as completely as you can [15 pts] % Source Type III Sum of Squares df Mean Square F Sig. Partial Eta Squared Observed Powerb Age 71.768 3 23.9 153.6 .000 .665 1.000 Crowding 60.823 1 60.8 390.7 .000 .627 1.000 Age * Crowding 82.832 3 27.6 177.4 .000 .696 1.000 Error 36.108 232 .16 Corrected Total 251.531 239 0.511.522.533.56 mo 9 mo 12 mo 15 moFarzin et al. 2010ThresholdAgeUncrowdedCrowdedExam%3%'%2%of%7%Homogeneity of Variance: The Levene Test is significant, so you’d be concerned about heterogeneity of variance and proceed with α = .01. However, all the effects are significant with p < .001, so they’d be significant regardless of the α-level you choose. [Had you chosen to compute Hartley’s FMax, you’d have arrived at the same conclusion, with FMax = 8.2 and FMax Crit = 3.12.] !"# = ! . !". !"!"=. !! There is a significant main effect of Age, F(3,232) = 153.6, MSE = .16, p < .001, η2 = .665. There is a significant main effect of Crowding, F(1,232) = 390.7, p < .001, η2 = .627. There was also a significant interaction between Age and Crowding, F(3,232) = 177.4, p < .001, η2 = .696. Using Tukey’s HSD, the interaction (as seen in the figure) arises because at 6 months of age, the eccentricity threshold for Crowded pictures is greater than for Uncrowded pictures. However, for 9-, 12-, and 15-month-olds, the eccentricity threshold for Uncrowded pictures is greater than for Crowded pictures. OR For Crowded pictures, the eccentricity threshold was greater for 15-month-olds than for all other ages, 6-month-olds had higher eccentricity thresholds than 9- and 12-month-olds. However, for the Uncrowded pictures, 9-, 12-, and 15-month-olds had higher eccentricity thresholds than did 6-month-olds. 2. In an article by Roelofs et al. (2010) in Psychological Science entitled “Facing freeze: Social threat induces bodily freeze in humans,” the abstract reads: Freezing is a common defensive response in animals threatened by predators. It is characterized by reduced body motion and decreased heart rate (bradycardia). However, despite the relevance of animal defense models in human stress research, studies have not shown whether social threat cues elicit similar freeze-like responses in humans. We investigated body sway and heart rate in 50 female participants while they were standing on a stabilometric force platform and viewing cues that were socially threatening, socially neutral, and socially affiliative (angry, neutral, and happy faces, respectively). Posturographic analyses showed that angry faces (compared with neutral faces and happy faces) induced significant reductions in body sway. In addition, the reduced body sway for angry faces was accompanied by bradycardia and correlated significantly with subjective anxiety. Together, these findings indicate that spontaneous body responses to social threat cues involve freeze-like behavior in humans that mimics animal freeze responses. These findings open avenues for studying human freeze responses in relation to various sociobiological markers and social-affective disorders. The female subjects completed the State-Trait Anxiety Index (STAI), which is a 20-item questionnaire with each response on a 4-pt scale. Thus, as used in this study, the scores could range from 0 (low anxiety) to 80 (high anxiety). The subjects looked at faces while their body sway was measured. The faces exhibited a neutral, happy, or angry emotion. The body-sway difference score in the analysis below is calculated by subtracting body-sway variability in the neutral faces block from the same measure in the angry-faces block. Thus, a difference score of 0 would indicate that body sway was the same when viewing neutral and angry faces. However, a negative difference score would indicate that body sway was reduced for angry faces compared to neutral faces. And a positive difference score would indicate that body sway was greater for angry faces compared to neutral faces. From the SPSS analysis below (of data that mimic those found in the Roelofs et al. study), interpret the results as completely as you can. How many participants are in the study? If a person received a score of 30 on the STAI, what would you predict that person’s Body-Sway Difference score to be? If a person