First impressions: it’s ironic how something that lasts so long is made so fast.
In fact, studies have demonstrated that it only takes 100 milliseconds to create a first impression about a stranger.  To put that into perspective, it takes three to four times longer for a human being to blink. Oddly enough, giving someone additional time doesn’t improve the judgements made. According to researchers Janine Willis and Alexander Todorov, “When exposure time increased from 100 to 500 ms, participants’ judgments became more negative, response times for judgments decreased, and confidence in judgments increased.”  In other words, increased exposure to others was found to increase the confidence behind the impressions made instead of alter the judgements made for the better.
During the 100ms, the human brain pieces together information from memories, past personal experiences, and intrinsic values to generate calculated judgements. Scientists at Harvard College and New York University analyzed the neuroscience of first impressions by identifying with which areas of the brain were most involved.  They presented fictional personalities to test subjects, added positive and negative qualities about each person, then asked the test subjects to evaluate how much they favored the fictional persona.
They used an fMRI (functional Magnetic Resonance Imaging) scanner to determine stimulated regions of the brain while presenting the fictional personas. An fMRI scanner uses a strong magnetic field and radio waves to analyze blood flow in the brain and thus map the areas of the brain are most active at a given moment in time. The two brain regions that were found to be most influential in commandeering the formation of these impressions were the amygdala and posterior cingulate cortex (PCC.)
The amygdala is an almond-sized structure located near the the back end of the brain. Despite its deceptively small size, it is incredibly powerful in its ability to combine learned qualities from memories with emotions from past experiences to enhance learning.  Studies have shown that this is also where social stimuli are processed, where we determine trustworthiness, and where we evaluate the harmfulness of objects we encounter. 
The posterior cingulate cortex, on the other hand, is a region of the brain under the intersection of the frontal and parietal lobes, which are the front and middle parts of your outer brain respectively. It is responsible for decision-making and evaluating rewards. In fact, patients lacking a PCC have a hard time assigning relative importance to material objects.  If you take a step back, it might be unsettling to realize that we use the same part of our brain to distinguish between cheap and valuable physical objects as we do to distinguish between people we like and people we dislike. That is a testament to how superficial these judgements can end up becoming — our brains ultimately evaluate people using the same skills we might to get a deal on Black Friday. The researchers also found that the first impressions were heavily influenced by the evaluation of how much value the fictional person presented would add to the test subject’s life.  This again presents first impressions as a way to befriend solely for personal gain, but also aligns with theories of evolution that state that humans developed first impressions to avoid interactions with dangerous organisms.
Studies have also suggested that the significant use of media can largely affect how you form first impressions.  According to the psychology researcher Richard Lopez of Rice University, “People who reported frequent media multitasking were more likely to be distracted by irrelevant information when making first impressions about someone they had never met, compared with those who did not engage in frequent media multitasking.”  The act of multitasking with media made others judge based on meaningless characteristics, thus altering first impressions significantly. Their study showed that it might not necessarily be for the worst — people who are heavily involved with media actually had higher opinions of strangers than the control group of people who limited their usage of media.  Considering that the average American spends more than 11 hours a day interacting with media, that raises serious questions about the first impressions that most of us are making. 
Researchers at Brandeis University focused on a separate aspect of first impressions: how they are stored in our memories.  They uncovered a third region of the brain integral to remembering first impressions: the dorsomedial prefrontal cortex (dmPFC.) The dmPFC is in the upper half of the prefrontal cortex (which is located in the front of the brain) and is typically involved in creating a sense of self and identity. This aligns with its role in first impressions because humans tend to assign strangers a distinct identity in their mental worlds. This is how we can ultimately evaluate their characteristics and determine their value. Interestingly, impressions made with conscious intent and those with definite opinions rather than neutral judgements last longer in the dmPFC.  This gives me hope as it shows that impressions that we think about using data we consciously obtain help solidify these thoughts for an impression that lasts longer but also indicates that bad first impressions are harder to erase.
That brings me to my final point: how does the science connect to our daily lives? The key reason that scientists would concern themselves with first impressions is that they can influence important decisions without any factual information. Because creating first impressions can be such an innate and accepted action, these underlying biases can be overlooked.  For example, many women aren’t seen as leaders because females are generally not associated with authority.  These biases can be terrifying when these superficial judgements are carried to the polls or to court. However, at the end of the day, given the situation, the best we can do is understand the science behind what is happening and try to use it to our advantage.
Edited by: Akshay Balaji
Illustrated by: Eugenia Yoh