Let's see how their memory is after holding down a job, raising kids, worrying about retirement, mortgage payments, bills, next OCI, etc. etc. All that stuff just wears you down.
The amazing part is getting the chimp to identify 1-9. I don't find the processing time difference all that remarkable. If the challenge was climbing a ladder the college students would have scored right up there until it was required to use only hands.
When it comes to scent, my dog has better memory skills than most humans too. Except maybe Lt. Col. Frank Slade or perhaps Lt. Col. Bill Kilgore