Delay of gratification by orangutans (Pongo pygmaeus) in the accumulation task
Journal of Comparative Psychology (2014) - Comment
pubmed: 24611642  doi: 10.1037/a0035660  issn: 1939-2087  issn: 0735-7036 

Audrey E. Parrish, Bonnie M. Perdue, Erin E. Stromberg, Amanda E. Bania, Theodore A. Evans, Michael J. Beran