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The information about age, gender, and genetic relatedness contained in ratings of facial similarity
No full textSuppose that you are told that two children — whom you have never seen — are very similar in appearance. Do you now imagine that they are more likely to be siblings? More likely to be close in age? More likely to be the same gender?
What objective information about age, gender, and genetic relatedness is conveyed by a rating of similarity?
We asked observers to rate the facial similarity of pairs of children depicted in photographs. Observers were not instructed to consider the ages, genders, or possible relatedness of the children: they were told only to rate facial similarity. We estimated the Shannon information (“bits”) about relatedness, age difference, and gender difference contained in these ratings of facial similarity.
The stimuli were 48 pairs of color photographs of children (3 to 12 years of age) from two provinces of northern Italy. Each photograph depicted the child from the shoulders to the top of the head with his or her face clearly visible. Half of the 96 children were male, and half female. In half of the pairs, the children were siblings, in the other half, the children were not related. Age difference, gender difference, and relatedness were counterbalanced across the pairs. Thirty observers rated the similarity of the 48 pairs on a scale of 0 to 10.
The maximum possible Shannon information that can be conveyed concerning a binary choice is 1 bit. The estimated Shannon information conveyed by a similarity rating was 0.171 bits (relatedness), 0.091 (gender difference), and 0.015 (age difference). The first two values are significantly greater than 0 (p 0.05). We conclude that the observers incorporate information about relatedness and gender difference into their ratings, but include little information relevant to age difference. In particular, the observers discounted the large physical changes in appearance that occur as children grow in forming a judgment of facial similarity
Where are kin recognition cues in the face? Annual Meeting of the Vision Sciences Society
No full textObservers accurately judge children's degree of kinship given facial photographs (Dal Martello & Maloney, VSS2002). We report two experiments intended to determine where in the face the cues signalling kinship fall. Since the upper face changes less than the lower during development (Enlow & Hans, 1996), we hypothesized that observers would rely on age-invariant features in the upper face. Stimuli:30 pairs of photographs, each photograph portraying a child's face with background removed. Half were of siblings, half, unrelated. The children's ages spanned 14 years. Observers: 220 observers judged each pair as siblings or not. We summarized performance in each condition by signal detection d' estimates. Experiment 1 Conditions: Full Face visible (FF); Upper Half face visible (UH); Lower Half face visible (LH). Different observers participated in each condition. Results: Performance in FF (d' = 1.19) and in UH condition (d''=1.12) did not differ significantly (p = n.s.). Performance in LH (d' = 0.41) was significantly lower (p < 0.0001) than that in other conditions.
Experiment 2 Conditions: Full Face visible (FF); face visible except for a small mask over the eye region (ME); face visible except for the masked mouth (MM). Results: Performance in the masked conditions (ME d' = 0.82; MM d' = 1.11) was not significantly different from that found in FF (d' = 1.02).
Conclusion: Observers (correctly) use kinship cues in the upper half face but, surprisingly, the eye region either provides little information or cues available in that region are redundant with other facial cues
Where are kin recognition signals in the human face?
No full textWe report two experiments intended to determine where in the face the cues signalling kinship fall. In both experiments, participants were shown thirty pairs of photographs of children’s faces. Half of the pairs portrayed siblings and half did not. The 220 participants were asked to judge whether each pair of photos portrayed siblings. We measured the effect on kin recognition performance of masks that covered the upper half of the face or the lower half (Experiment 1) and the eye region or the mouth region (Experiment 2). In Experiment 1 we found that the signal detection estimate of performance decreased only 5.3% (n.s.) when the lower face was masked but by more than 65% when the upper face was masked. We tested whether combination of kinship information from the two halves of the face can be treated as optimal combination of independent cues and found that it could be. In Experiment 2, we found that masking the eye region led to only a 20% reduction (n.s.) in performance while masking the mouth region led to a non-significant increase in performance. We also found that the eye region contains only slightly more information about kinship than the upper half of the face outside of the eye region
How the past gives way to the present: Evidence for Bayesian updating with repeated presentation of ambiguous motion quartets
No full textIntroduction: In a motion quartet (MQ)with one repetition, two disks that fall at the endpoints of a diameter of an invisible circle are briefly presented and then replaced by two disks that fall on a second diameter. The observer sees rotation of the first pair into the second. By varying the angle between the diameters, one can estimate a psychometric function P[L|angle]. We reported last year that recent task history exerted a strong effect on perceived direction of motion, shifting the threshold parameter of the psychometric function. In particular, the observer is strongly biased to see motion in the same direction as the motion perceived on the most recent trial. This hysteretic effect (measured as the change in threshold) is little affected by increasing the time interval between trials (to as much as 30 seconds). Purpose: We sought to determine how repetitions of the same motion quartet would affect hysteresis. It is plausible, for example, that multiple presentations of the same sensory information would eventually ‘overpower’ the influence of recent task history, reducing hysteresis to 0. But precisely how? Methods: We measured the hysteresis induced by the previous trial for two subjects who judged 3840 MQ trials each. In different blocks, the MQ was presented 1, 2, 4 or 8 times in each trial. The observer reported the direction of motion of the last presentation only. Results: For both observers we found that hysteresis decreased rapidly with number of repetitions and that a log-log plot of hysteresis versus repetition was approximately linear with slope −1. Doubling the number of repetitions halves the hysteretic effect. This outcome is consistent with a Bayesian updating model where an initial prior probability that the stimulus will go left (based on recent task history) is successively combined with independent likelihood terms, one for each repetition of the stimulus
Movement planning under risk differs from decision making under risk in how subjects make use of probability information.
No full textTrommershäuser, Maloney & Landy (JOSA, 2003) studied performance in tasks that were formally equivalent to decision making under risk. They found that subjects' planned movements nearly maximized expected gain, a result inconsistent with the decision making literature. Here we replicated a decision making experiment (Wu & Gonzalez, Management Science,1996) that tested whether subjects correctly use probability information in choosing between lotteries. We replicate the original experiment with the probabilities of outcomes explicitly given in the lotteries and we also replicated the experiment with each lottery translated into an equivalent motor task (“motor lottery”) where the probability of each outcome is implicit in movement uncertainty. We will describe how we measured subjects' movement uncertainty and designed an equivalent motor lottery for any given lottery. Each subject ran the implicit and explicit conditions in counterbalanced order. Task: On each trial in both conditions subjects indicated which lottery/motor lottery they preferred (2AFC). They knew that, at the end of the experiment, they would be allowed to attempt only one of their preferred explicit lotteries and one of their preferred implicit motor lotteries chosen at random and receive the outcome. Results: All subjects failed to correctly use probability information or maximize expected gain in the explicit condition, consistent with Wu & Gonzalez. Five out of eight of these subjects made choices consistent with maximizing expected gain in the implicit (motor lottery) condition. The results indicate that planning rapid movements differs qualitatively from classical decision making in how subjects make use of probability information
Judgments of genetic relatedness of children
No full textOur object was to estimate the information about genetic relatedness visually available from facial photographs of children. The stimuli were forty-eight pairs of photographs of children. In half of the pairs, the children were siblings; in the other half, the children were not. Forty-eight observers, in a signal-detection task, judged which pairs depicted siblings. There were three occlusion conditions: sixteen observers viewed full-face photographs of the children, sixteen viewed the same photographs with the eye regions of both children masked, and sixteen viewed the photographs with the mouth regions masked. For each occlusion condition, we converted the observers' performances into estimates of Shannon information, an alternative to signal-detection measures that require distributional assumptions. The maximum possible information conveyed per pair is 1 bit. The results for each occlusion condition were: 0.36 bit (full face), 0.47 bit (eyes masked), 0.63 bit (mouth masked). We find that observers can extract considerable information about genetic relatedness from photographs of children's faces. It is remarkable that observers were able to extract more information with parts of the face occluded than they could from full faces, as if the intact face masked the facial features relevant to the task
Where is kinship information in the child's face? Signal detection study finds no evidence for lateralization.
No full textPurpose. Dal Martello & Maloney (2006, JOV ) report signal detection experiments measuring the amount of kinship information in the upper and lower halves of children's faces. They found that the upper and lower halves each contained significant information about kinship with the upper half of the face containing considerably more than the lower. The information in the two halves was statistically independent.
Previous work has shown that information about age, attractiveness, gender, identity, expression and lip-reading tends to be left-right lateralized. We test whether this is the case for kinship.
Methods. Stimuli: 30 pairs of photographs, each photograph portraying a child's face with background removed. Half were of siblings, half, unrelated. The children's ages spanned 14 years. Observers: 124 adult observers who judged each pair as siblings or not. We summarized performance in each condition by signal detection estimates d′ and β. Conditions: Full Face visible (FF); Right Half visible (RH); Left Half visible (LH). Different observers participated in each condition.
Results. Performance in FF (d′ = 1.079) did not differ significantly (p = n.s.) from performance in RH condition (d′ = 1.024) or from performance in LH (d' = 1.004). Performance in RH and LH did not differ significantly (p = n.s.). The beta values of FF (β = 0.888) and RH (β = 0.896) did not differ (p = n.s.) and indicated an equal bias towards saying related. The beta for LH (β = 1.102) differed significantly (p = 0.0001) from betas on the other conditions.
Conclusion. Kinship cues appear to be evenly distributed across the vertical halves of the face and completely redundant. There is no superiority of one or the other side of the observed face for kinship. Observers have a bias against saying 'related' when the right half of the face is masked
The effect of past trials on perceived direction of motion in ambiguous motion quartets: temporal pattern detection, not priming
No full textIn a motion quartet (MQ), two disks that fall at the endpoints of a diameter of an invisible circle are briefly presented and then replaced by two disks that fall on a second diameter. With proper choice of timing, the observer sees apparent rotation of the first pair into the second. When the angle between the diameters is about 90 deg, the direction of perceived rotation is ambiguous, half the time clockwise (C) and half counterclockwis
Trajectory planning in sequential pointing movements. Bridging the gap between sensation and motor control: from computation to behavior
No full textLateralization of Kin Recognition Signals in the Human Face
No full textWhen human subjects view photographs of faces, their judgments of identity, gender, emotion, age and attractiveness depend more on one side of the face than the other. We report an experiment testing whether allocentric kin recognition (the ability to judge the degree of kinship between individuals other than the observer) is also lateralized. One hundred and twenty four observers judged whether or not pairs of children were biological siblings by looking at photographs of their faces. In three separate conditions (1) the right hemi-face was masked, (2) the left hemi-face was masked, or (3) the face was fully visible. The measures for the masked left hemi-face and masked right hemi-face were 1.024 and 1.004 respectively (no significant difference) and the measure for the unmasked face was 1.079, not significantly greater than that for either of the masked conditions. We conclude, first, that there is no superiority of one or the other side of the observed face in kin recognition, second, that the information present in the left and right hemi-face relevant to recognizing kin is completely redundant, and last that symmetry cues are not used for kin recognitio
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