Monkeys and humans implement causal inference to simultaneously localize auditory and visual stimuli.

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• The brain integrates information from multiple senses to create a unified perception.
• Optimal integration requires determining if sensory signals originate from the same or different sources.
• Previous research primarily focused on information fusion, with limited exploration of causal inference in animals.

Purpose of the Study:

• To investigate multisensory causal inference in both humans and nonhuman primates (Macaca mulatta).
• To compare how humans and monkeys determine the number and location of sensory sources.
• To test a hierarchical causal inference model in a novel behavioral task.

Main Methods:

• Developed a novel behavioral paradigm involving simultaneous visual and auditory stimuli localization.
• Recorded saccadic eye movements to report perceived stimulus sources.
• Analyzed response patterns (single vs. multiple saccades) and localization biases.
• Modeled behavioral data using a hierarchical causal inference framework.

Main Results:

• Both humans and monkeys exhibited distinct behavioral patterns based on stimulus separation.
• A single saccade was observed for co-located stimuli, while separate saccades occurred for widely separated stimuli.
• The hierarchical causal inference model accurately predicted "same vs. different" source judgments and localization biases.
• Behavioral responses in both species were consistent with Bayes-optimal causal inference.

Conclusions:

• This study demonstrates behavioral causal inference in nonhuman primates for the first time.
• Humans and monkeys employ similar, Bayes-optimal strategies for multisensory causal inference.
• The findings provide a foundation for future cross-species neurophysiological investigations of multisensory processing.