What are we studying?
The human brain consists of two separate hemispheres, each of which is specialized to process particular kinds of information. For example, the left hemisphere is primarily responsible for language processing, speech, controlling the right side of the body, time perception, arithmetic abilities, and perceiving visual information presented on the left side of the world. The right hemisphere, on the other hand, is responsible for spatial processing, imagery, face recognition, holistic processing, controlling the left side of the body, and perceiving visual information presented on the right side of the world. Lateralization of cerebral functions are vital for efficient cognitive functioning as they increase the speed of information processing (Ringo et al., 1994). Further, since the two hemispheres are specialized to process different information, the amount of information that can be processed by the brain at one time is effectively doubled (Rogers et al., 2004; Ocklenburg & Güntürkün, 2012; Vallortigara, 2006).
Another process that is strongly lateralized to one cerebral hemisphere is visual attention. Our visual world is incredibly rich and complex, meaning that we are unable to process all of the information entering our eyes at one time. Attention allos us to select just the relevant visual information for processing while ignoring or filtering out the irrelevant information. The control of visual attention is lateralized in the right cerebral hemisphere, resulting in a bias to processing visual information presented in the left half of the world. This leftward bias has been shown in many situations. For example, if you ask people to identify the midpoint in a line, they will usually specify a point slight to the left of the true midpoint. In addition, if looking for an item in a cluttered drawer, they will usually look on the left side of the drawer before the right side of the drawer. This left bias even extends to facial processing, with people's perceptions of faces and emotional expressions being driven by the information in the left side of a face.
Although much is known about visual field asymmetries, many basic questions are as yet unanswered. In the present study we are testing how task difficulty influences how strong a left bias people experience.
What research methodology was used?
Our research is based on a previous study by Verleger et al., (2009). They used a paradigm known as a dual-stream attentional blink paradigm to study visual field asymmetries. In this task, people are presented with two rapid streams of digits, one to the left and one to the right of a central point. The task is to identify letter targets, which appear in either the left stream or the right stream.
In this study, we had three independent variables:
(a) the location of the targets (left or right stream)
(b) the number of targets (1-4), and
(c) the task that must be performed with the targets (simply detect that a target was present or identify the target)
The Dependent Variable was how accurately participants were able to detect or identify the targets.
What did we find?
We found a strong left bias, with people being significantly more accurate at identifying the targets when they were in the left stream compared to when they were in the right stream. The magnitude of the left bias got stronger as we increased the number of letter targets and made the task more difficult (it is more difficult to identify a target than to detect its presence).
Curious to learn more about attention or visual cognition? Here are some books that you might enjoy:
Chabris, C. F., & Simons, D. J. (2010). The invisible gorilla: And other ways our intuitions deceive us. Harmony.
Doidge, N. (2007). The brain that changes itself: Stories of personal triumph from the frontiers of brain science. Penguin. (Available as an e-book in the City of Gold Coast public library via Overdrive)
Kahneman, D. (2011). Thinking, fast and slow. Macmillan. (Available as an e-book in the City of Gold Coast public library via Overdrive)
Gladwell, M. (2006). Blink: The power of thinking without thinking. (Available as an e-book in the City of Gold Coast public library via Overdrive)