The Invisible Gorilla

BRAIN AREA: Cerebral Cortex – Occipital Lobe – Vision

The famous Invisible Gorilla experiment addresses the question of how much of our surroundings we actually see. More specifically, it demonstrates inattentional blindness, which occurs where we fail to see an object due to our attention being directed elsewhere. In the Invisible Gorilla experiment, observers were focused on counting passes by a team throwing a ball. Many failed to see a person dressed as a gorilla walking through the players, showing that our vision and perception is different to a camera recording an event – much of our visual processing is involved in making sure we see what is important to us while filtering out the rest.

In a normal vision path our visual processing consists of a pathway proceeding from V1 (general scanning) to V5 (motion). However, one outcome of the Invisible Gorilla experiment is to provide us with a strong hint that there is more to vision than simply seeing what is in front of us. Another clue regarding the complexity of vision is the fact that almost half of the cortex we see when we look at the surface of the brain is involved in visual processing*, indicating there is far more to vision than the pathway from the eye to the occipital cortex and nearby areas (V1 to V6).

One effect of this extensive neuron power is the capacity of the brain to present to us what it wants us to see. Therefore, an important role of the brain in vision is to filter out distractions. This is achieved using areas of the brain involved in deciding what we pay attention to, notably the frontal cortex and parietal cortex (see Image 1), and brainstem areas such as the tiny locus coeruleus (this nucleus is deep within the pons seen in Image 8).

In the particular case of the Invisible Gorilla experiment, the gorilla is merely a distraction. Therefore, the brain may eliminate it from what we see in case our attention is taken away from what we are supposed to be doing, which is counting the number of times the ball is passed.

*This estimate by Kandel et al (2021) differs from that by the Society for Neuroscience (2018) with the latter stating that the visual system involves about 30 percent of human cerebral cortex. However, the discrepancy between the two estimates is largely due to Kandel et al (2021) including not only oculomotor areas but also prefrontal areas contributing to visual memory.

References & further reading

Chabris, C., & Simons, D. (2010). Gorilla Experiment. The Invisible Gorilla. http://www.theinvisiblegorilla.com/gorilla_experiment.html

Drew, T., Vo, M. L. H., & Wolfe, J. M. (2013). The invisible gorilla strikes again: Sustained inattentional blindness in expert observers. Psychological Science, 24(9), 1848–1853. https://doi.org/10.1177/0956797613479386

Simons, D. J., Chabris, C. F. (1999). Gorillas in our midst: Sustained inattentional blindness for dynamic events. Perception, 28(9), 1059–1074. https://doi.org/10.1068/p281059