Volume 26, Issue 13, Pages 1744-1749 (July 2016) Motivational Shifts in Aging Monkeys and the Origins of Social Selectivity  Laura Almeling, Kurt Hammerschmidt, Holger Sennhenn-Reulen, Alexandra M. Freund, Julia Fischer  Current Biology  Volume 26, Issue 13, Pages 1744-1749 (July 2016) DOI: 10.1016/j.cub.2016.04.066 Copyright © 2016 Elsevier Ltd Terms and Conditions

Current Biology 2016 26, 1744-1749DOI: (10.1016/j.cub.2016.04.066) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Aging and Exploratory Behavior Barbary macaques’ exploration times of animal toys (A), a cube (B), and an opaque tube baited with peanuts (C), indicating that the age-related change in interest during adulthood was modulated by the potential availability of a food reward (permutation test of linear mixed model [LMM]: n trials = 192, n subjects = 93; age × novel object type, p < 0.05). See also Movies S1, S2, and S4. Current Biology 2016 26, 1744-1749DOI: (10.1016/j.cub.2016.04.066) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 Aging and Problem-Solving Behavior Old subjects (>19 years) failed to retrieved the peanut out of the tube (generalized linear model [GLM]: n trials and subjects = 53; age, χ2 = 11.81, df = 1, p < 0.001; sizing of points corresponds to number of subjects [1–6] tested at a certain age) (A), and the latency to open the tube steadily increased from young adulthood on (Spearman-rank correlation: n trials and subjects = 21, rho = 0.61, p < 0.01) (B). See also Movies S3, S4, and S5. Current Biology 2016 26, 1744-1749DOI: (10.1016/j.cub.2016.04.066) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 3 Preferential Interest for Different Types of Social Partners (A) Males spent more time looking at photographs (LMM with log10-transformed response: n subjects = 44 in one to three experimental conditions, n trials = 85) depicting an infant of conspecifics (I) than a close friend (CF) (estimate = −0.32, SE = 0.09) or a non-friend (NF) (estimate = −0.22, SE = 0.09). (B) Females spent more time looking at photographs (LMM with log10-transformed response: n subjects = 54 in one to three experimental conditions, n trials = 127) depicting an infant of conspecifics (I) (estimate = −0.27, SE = 0.08) or a close friend (CF) (estimate = −0.18, SE = 0.09) compared to a non-friend (NF). See also Movie S6. (C) Females looked longer toward the loudspeaker after playback of close friend’s (CF) compared to non-friend’s (NF) recruitment screams (permutation test of LMM with log10-transformed [after adding c = 1] response: n subjects = 47 in one to two experimental conditions, n trials = 69). See also Movie S7. Current Biology 2016 26, 1744-1749DOI: (10.1016/j.cub.2016.04.066) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 4 Aging and Grooming Behavior Depicted are the estimated (mixed additive distributional regression, MADR) 2.5%, 10%, 25%, 75%, 90%, and 97.5% quantiles (shaded areas) and expected values (line) of the respective response distribution over the domain of age (n observations = 68, n subjects = 45). Pairs of values with exclusive expected values and inner 97.5% quantile intervals reveal strong evidence for age-related distributional differences. With increasing age, female Barbary macaques engaged less in active grooming (A) and had a lower number of adult partners they actively groomed (active partners) (B). There was no substantial change in the time females received grooming (C) or the number of adult partners by which females were groomed (passive partners) (D). Current Biology 2016 26, 1744-1749DOI: (10.1016/j.cub.2016.04.066) Copyright © 2016 Elsevier Ltd Terms and Conditions