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Event-based proactive interference in rhesus monkeys
Deepna T Devkar1, Anthony A Wright2
1Department of Neurobiology & Anatomy, The University of Texas Medical School, Houston, TX, 77030, USA. deepna.85@gmail.com.
Abstract:
Three rhesus monkeys (Macaca mulatta) were tested in a same/different memory task for proactive interference (PI) from prior trials. PI occurs when a previous sample stimulus appears as a test stimulus on a later trial, does not match the current sample stimulus, and the wrong response "same" is made. Trial-unique pictures (scenes, objects, animals, etc.) were used on most trials, except on trials where the test stimulus matched potentially interfering sample stimulus from a prior trial (1, 2, 4, 8, or 16 trials prior). Greater interference occurred when fewer trials separated interference and test. PI functions showed a continuum of interference. Delays between sample and test stimuli and intertrial intervals were manipulated to test how PI might vary as a function of elapsed time. Contrary to a similar study with pigeons, these time manipulations had no discernable effect on the monkey's PI, as shown by compete overlap of PI functions with no statistical differences or interactions. These results suggested that interference was strictly based upon the number of intervening events (trials with other pictures) without regard to elapsed time. The monkeys' apparent event-based interference was further supported by retesting with a novel set of 1,024 pictures. PI from novel pictures 1 or 2 trials prior was greater than from familiar pictures, a familiar set of 1,024 pictures. Moreover, when potentially interfering novel stimuli were 16 trials prior, performance accuracy was actually greater than accuracy on baseline trials (no interference), suggesting that remembering stimuli from 16 trials prior was a cue that this stimulus was not the sample stimulus on the current trial-a somewhat surprising conclusion particularly given monkeys.
Insights
Rhesus monkeys exhibit proactive interference (PI) in memory tasks, where prior stimuli disrupt current recall. Interference depends on the number of intervening trials, not elapsed time, suggesting event-based memory processing.
Area of Science:
- Cognitive psychology
- Primate behavior
- Neuroscience
Background:
- Proactive interference (PI) is a memory phenomenon where prior learning impedes new learning.
- Understanding PI in non-human primates offers insights into memory mechanisms.
- Rhesus monkeys were used to investigate PI in a same/different memory task.
Purpose of the Study:
- To investigate proactive interference (PI) in rhesus monkeys using a same/different memory task.
- To determine if PI is influenced by the number of intervening trials or elapsed time.
- To compare PI effects in monkeys with those observed in pigeons.
Main Methods:
- Three rhesus monkeys performed a same/different memory task with trial-unique pictures.
- Proactive interference was manipulated by reintroducing prior sample stimuli at varying trial intervals (1, 2, 4, 8, 16 trials prior).
- Time delays between sample and test stimuli, and intertrial intervals were varied.
Main Results:
- Greater PI occurred when fewer trials separated the interfering stimulus and the current trial.
- Time manipulations (delays, intertrial intervals) did not significantly affect PI levels.
- PI appears to be event-based, depending on the number of intervening trials rather than absolute time.
Conclusions:
- Rhesus monkeys' PI is primarily driven by the number of intervening events, not elapsed time.
- This suggests an event-based memory system in monkeys, differing from some interpretations in other species.
- Novel stimuli elicited greater PI than familiar stimuli, with a surprising accuracy increase when interference was 16 trials prior.
