Visible and invisible displacement with dynamic visual occlusion in bottlenose dolphins (Tursiops spp)

Abstract

Anticipating the location of a temporarily obscured target—what Piaget (the construction of reality in the child. Basic Books, New York, 1954) called ‘‘objectpermanence’’—is a critical skill, especially in hunters of mobile prey. Previous research with bottlenose dolphins found they could predict the location of a target that had been visibly displaced into an opaque container, but not one that was first placed in an opaque container and then invisibly displaced to another container. We tested whether, by altering the task to involve occlusion rather than containment, these animals could show more advanced object permanence skills. We projected dynamic visual displays at an underwater-viewing window and videotaped the animals’ head moves while observing these displays. In Experiment 1, the animals observed a small black disk moving behind occluders that shifted in size, ultimately forming one large occluder. Nine out of ten subjects ‘‘tracked’’ the presumed movement of the disk behind this occluder on their first trial—and in a statistically significant number of subsequent trials—confirming their visible displacement abilities. In Experiment 2, we tested their invisible displacement abilities. The disk first disappeared behind a pair of moving occluders, which then moved behind a stationary occluder. The moving occluders then reappeared and separated, revealing that the disk was no longer behind them. The subjects subsequently looked to the correct stationary occluder on eight of their ten first trials, and in a statistically significant number of subsequent trials. Thus, by altering the stimuli to be more ecologically valid, we were able to show that the dolphins could indeed succeed at an invisible displacement task.

More than a Fluke: Lessons Learned from a Failure to Replicate the False Belief Task in Dolphins

“…However, as has been cautioned by a number of researchers, low-level associative explanations must be controlled for in these studies (e.g., Andrews, 2017;Heyes, 2014). Finally, experimental procedures that harness ecological validity have been more successful in demonstrating advanced aspects of ToM and complex social behaviors than the more artificial procedures in primates and dolphins (e.g., Buttelmann, Buttelmann, Carpenter, Call, & Tomasello, 2017;Hare, 2001;Johnson et al, 2015;Kaminski et al, 2008;Kano et al, 2017;Krupenye et al, 2016). For example, Johnson et al (2015) successfully modified the traditional container testing paradigm for invisible displacement with dolphins by adapting an occlusion method and gaze direction measure successfully utilized with human infants, which evidences the need for an adaptable comparative approach (Onishi & Baillergeon, 2005;Surian, Caldi, & Sperber, 2007).…”

“…Finally, experimental procedures that harness ecological validity have been more successful in demonstrating advanced aspects of ToM and complex social behaviors than the more artificial procedures in primates and dolphins (e.g., Buttelmann, Buttelmann, Carpenter, Call, & Tomasello, 2017;Hare, 2001;Johnson et al, 2015;Kaminski et al, 2008;Kano et al, 2017;Krupenye et al, 2016). For example, Johnson et al (2015) successfully modified the traditional container testing paradigm for invisible displacement with dolphins by adapting an occlusion method and gaze direction measure successfully utilized with human infants, which evidences the need for an adaptable comparative approach (Onishi & Baillergeon, 2005;Surian, Caldi, & Sperber, 2007). The training and testing protocols used by Brosnan and her colleagues in their investigations of cooperation, decision making, and equity using variations of the "Stag Hunt" game or the Assurance game are excellent examples of ecologically valid methodologies that require limited training and enable cross-species comparisons (Brosnan et al, 2011).…”

“…If this experimental set-up can be automated, then the influence of humans is removed and any outcome is less confounded. Increasingly, research designs are becoming more innovative as the perspective and abilities of the various subjects are recognized and incorporated (i.e., Abramson, Dinges, & Wells, 2009;Buttelmann et al, 2017;Johnson et al, 2015) and will be more successful and valid in demonstrating whether or not specific cognitive abilities exist.…”

“…For example, nonverbal tasks, measuring cognitive skills such as pointing, attention, or perspective-taking in human children have been adapted to test apes and chimpanzees from a comparative approach (Beran, 2017;Byrne & Whiten, 1988;Maestripieri, 2003). Only recently have these tasks been extended beyond primates (attention: Herman et al, 1999;2004, 2007Tschudin et al, 2001; object permanence: see review by Jaakkola, 2014;Johnson Sullivan, Buck, Trexel, & Scarpuzzi, 2015;Singer & Henderson, 2015; perspective-taking: see review by Pérez-Manrique & Gomila, 2017).…”

Prosocial Predictions by Bottlenose Dolphins (Tursiops spp.) Based on Motion Patterns in Visual Stimuli

“…Our dependent measure was whether the dolphin turned its head to the right or left during these 2 s in anticipation of the target reappearing on one side or the other of the occluder. Previous work with the same animals involving the occlusion of dynamic, 2-D images (judging visible and invisible displacement; see Johnson, Sullivan, Buck, Trexel, & Scarpuzzi, 2015) showed that they would often turn to look in the direction they expected an object to reappear. In rare cases, dolphins looked in more than one direction; for all of these cases, we counted the first head turn.…”