Objectives: The emergence of human-unique cognitive abilities has been linked to our species' extended juvenile period. Comparisons of cognitive development across species can provide new insights into the evolutionary mechanisms shaping cognition. This study examined the development of different components of spatial memory, cognitive mechanisms that support complex foraging, by comparing two species with similar life history that vary in wild ecology: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). Materials and methods: Spatial memory development was assessed using a cross-sectional experimental design comparing apes ranging from infancy to adulthood. Study 1 tested 73 sanctuary-living apes on a task examining recall of a single location after a 1-week delay, compared to an earlier session. Study 2 tested their ability to recall multiple locations within a complex environment. Study 3 examined a subset of individuals from Study 2 on a motivational control task. Results: In Study 1, younger bonobos and chimpanzees of all ages exhibited improved performance in the test session compared to their initial learning experience. Older bonobos, in contrast, did not exhibit a memory boost in performance after the delay. In Study 2, older chimpanzees exhibited an improved ability to recall multiple locations, whereas bonobos did not exhibit any age-related differences. In Study 3, both species were similarly motivated to search for food in the absence of memory demands. Discussion: These results indicate that closely related species with similar life history characteristics can exhibit divergent patterns of cognitive development, and suggests a role of socioecological niche in shaping patterns of cognition in Pan.
Memory Development Study 1: Trial Data (Rosati)
Trial data from Study 1 (Memory after a long delay). Key for variable codes included as a separate tab in the file.
Rosati-Memory-Development-Study1-DRYAD.xlsx
Memory Development Study 2: Subject Data (Rosati)
Subject data from Study 2 (Memory for multiple locations) comprising the first four locations searched during the task. Key for variable codes included as a separate tab in the file.
Rosati-Memory-Development-Study2-Subjects-DRYAD.xlsx
Memory Development Study 2: Trial Data (Rosati)
Trial data from Study 2 (Memory for multiple locations) including latencies for all searches. Key for variable codes included as a separate tab in the file.
Rosati-Memory-Development-Study2-Trials-DRYAD.xlsx
Memory Development Study 3: Subject Data (Rosati)
Subject data from Study 3 (Control) with comparisons to those subjects performance on Study 2 (Memory for multiple locations) comprising the first four locations searched during the tasks. Key for variable codes included as a separate tab in the file.
Rosati-Memory-Development-Study3-DRYAD.xlsx
Video S1: Long Delay - Bonobo
Video S1: Long Delay (Study 1) – Bonobo. Experimenter 1 (E1) baits and fake-baits the two containers (in counterbalanced order across trials) while Experimenter 2 (E2) attracts the bonobo to the centered starting location on the other side of the room. Once the baiting is complete, the bonobo approaches the left (correct) container and E1 then gives the food. In initial learning trials the ape could self-correct if they initially made an incorrect choice, whereas in test trials one week later they could not. Correct side was counterbalanced across individuals.
Video-S1-LongDelay-Bonobo.m4v
Video S2: Long Delay - Chimpanzee
Video S2: Long Delay (Study 1) – Chimpanzee. Experimenter 1 (E1) baits and fake-baits the two containers (in counterbalanced order across trials) while Experimenter 2 (E2) attracts the chimpanzee to the centered starting location on the other side of the room. Once the baiting is complete, the chimpanzee approaches the left (correct) container and E1 then gives the food. In initial learning trials the ape could self-correct if they initially made an incorrect choice, whereas in test trials one week later they could not. Correct side was counterbalanced across individuals.
Video-S2-LongDelay-Chimpanzee.m4v
Video S3: Multiple Locations - Bonobo
Video S3: Multiple Locations (Study 2) – Bonobo. The experimenter (E) initially hid four test pieces of food in the enclosure while the bonobo observed; four control pieces had been previously hidden while the ape was out of sight. The video shows the start of the search phase after a 10-minute delay following the baiting demonstration. This young bonobo is still in a nursery group, so a caretaker sits with her in the center of the enclosure (never providing any social cues). E signals to the caretaker that the 10-minute delay has concluded, and the bonobo is released. This subject rapidly approaches two test locations (a tree and a water pool). Test and control locations were counterbalanced across subjects tested in the same enclosure. This clip showed the first 30s of the search phase; the entire search phase lasted 10 min.
Video-S3-MultipleLocations-Bonobo.m4v
Video S4: Multiple Locations - Chimpanzee
Video S4: Multiple Locations (Study 2) – Chimpanzee. The experimenter (E) initially hid four test pieces of food in the enclosure while the chimpanzee observed; four control pieces had been previously hidden while the ape was out of sight. The video shows the start of the search phase after a 10-minute delay following the baiting demonstration. This chimpanzee observed the baiting from an adjacent tunnel and is released by a caretaker after E signals the 10-minute delay has concluded. This subject rapidly approaches two test locations (a grass patch and a water fountain). Test and control locations were counterbalanced across subjects tested in the same enclosure. This clip showed the first 30s of the search phase; the entire search phase lasted 10 min.
Video-S4-MultipleLocations-Chimpanzee.m4v
