How to Interpret Figures in MCAT Science Passages

It can feel very daunting when an MCAT question asks you to draw a conclusion from a figure. Whether it is deducing if a gene is dominant or recessive from a table or determining the relationship between the independent and dependent variables in a graph, a figure can make science passage questions tricky. However, these few tips can help you confidently interpret MCAT science passage figures and navigate your way to a higher score!

For more help with interpreting figures and understanding science passages, check out our Science Passage Reading Strategy Course.

Read the Figure Description

I first look at a figure when I see it referenced in the passage. If the passage text alludes to a figure explicitly (such as “Experiment A found x (Figure 1)”), I scroll down to look at the figure immediately. This way, I have context fresh in my mind for interpreting the graph or image; otherwise, I may forget key details by the end of that paragraph, and understanding the figure will be that much harder.

With my figure context in hand, I next read the figure description at the bottom of the image. Not only will this explain what the figure is depicting, but the description can also explain key variables, values, and even a formula at times. For example:

Figure 1 Reflectance spectra (percent reflectance compared to white standard) from the fur of five Ursus Maritmus subjects

In this description, we obtain valuable information for interpreting the graph: a definition of reflectance spectra! While it is tempting to jump ahead, the description can guide your interpretation and contain relevant information. You don’t want to spend extra time trying to recall outside content knowledge when the passage can give you the answer!

Read the Axes

If you have a graph, understanding the x- and y-axes will give you the independent and dependent variables of an experiment. This can help clarify the experimental design, the purpose of the study, and what conclusions you can draw from the results. The units of the axes can also tell you if you need to calculate the area inside of a curve or find a particular point in the graph to answer a question. 

For example, to understand the distance moved during a saccade (a type of eye movement) that lasted 50 ms in the graph below, one would need to multiply the saccade duration (50 ms) by the saccade velocity (0.2) to obtain a distance of 10 degrees.

Compare the Right Groups

This is especially relevant for interpreting tables where there is typically a positive or negative control with which you can compare experimental values. These will usually be indicated as wild-type (WT), or conditions in which no gene, chemical, etc. is added to the baseline situation. Numbers usually are not noteworthy in MCAT science passage figures (after all, what does 11% change mean without context?), but evaluating if a mutated gene significantly increases protein aggregation or apoptosis compared to a baseline value will give you so much more information! 

Table 1 Level of immune function in WT and Ccr5-/-  mice that underwent treatment of saline, shRNA (gene knockdown), CCR5 treatment

For example, in Table 1, we can compare WT mice that received saline (100%) with WT mice that received shRNA treatment (24%) to determine how CCR5 affects immune function. Since we see that immune function decreases with a gene knock-down treatment, we can hypothesize that CCR5 is important for proper immune function. We can also compare WT and Ccr5-/-  mice that underwent the same treatment: when both types of mice receive saline, immune function is much higher in the WT mice (100%) than in the Ccr5-/-  knockout mouse (12%), again indicating that CCR5 is critical for proper immune function.

Look for Trends

Understanding whether variables have a direct or indirect relationship can lead to the right answer. If you’re looking at a line graph, are the slopes of the lines positive? Do the values increase together? Do they increase linearly or exponentially? If I have a table, I’m not shy of noting exactly how much values change from row to row to assess the mathematical relationship between certain variables. In the table below for instance, as temperature increases in each row by 100℃, resistance increases by 2.4Ω. Because of this, I know temperature and resistance share a direct linear relationship.

Furthermore, if I come across an image of a complex molecular pathway, I will use my scratch paper to identify the inhibitory and excitatory mechanisms. For example, knowing Molecule A inhibits Protein B, which inhibits Enzyme C, can mean that Molecule A indirectly excites Enzyme C. Writing these down can help me keep track of the net effect of a complex signaling cascade and how manipulation of one compound can broadly influence a cell.

Don’t forget to look for whether these trends are statistically significant (p<0.05 or a graph with non-overlapping standard error bars)! When extrapolating figure information to a question, it’s important to notice which changes are due to the variability of the data and which trends you would expect to observe more consistently and robustly. Even if it looks like DNA methylation is increasing over time in a graph, if the data are not significant, you cannot assume that DNA methylation will increase in an answer choice.

Don’t Get Bogged Down by the Details

It’s easy to spend a ton of time trying to figure out a schematic in a figure only to have it never referenced again. Many schematics on the MCAT will include topics you already know, presented in what can be an overwhelming way. You can simplify schematics into systems you are already familiar with! For example, taking a complex optical system and separating it into individual lenses and mirrors that you understand can help you gain the gist of a schematic in a physics passage.

As soon as I finish reading a science passage, I forget all the names and acronyms of whatever I was just reading, and that’s okay! The actual nuances of the experiment are less important than critically thinking about how to design, execute, and interpret a study. Understanding trends and relationships are often enough to get you where you need to be to answer a question correctly, so don’t sweat the small stuff! 

A picture is worth a thousand words, and science passage figures are no exception! I hope you can use these tips for your benefit and crush your MCAT exam!

If you find you’re still struggling with MCAT science passages, please take a look at our Science Passage Reading Strategy Course or schedule a free 10-minute phone consultation with me or one of our incredible Elite MCAT Tutors. Good luck studying! 

Best,

Denisse Morales-Rodriguez

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