Test sensoriale del numero approssimato

The approximate number sense test is an experimental paradigm for investigating the underlying mechanisms that support the ability to “guesstimate.”

Guesstimating refers to an intuitive ability to recognize quantity, without knowing the exact number. For instance, in a common carnival game, individuals try to guess the number of jellybeans packed into a jar. The chances are low that anyone will pick the exact number.

Yet everyone can produce a guess in the right ballpark, as no one would guess 20 when there are clearly more than 100. Therefore, estimation is considered a hard-wired ability that individuals possess without relying on mathematical calculations.

This video demonstrates the procedure for investigating nonverbal numerical estimation, including how to design the stimuli, perform the experiment, and how to analyze and interpret data.

In this experiment, stimuli that vary in size and color are randomly and briefly presented on a computer screen. During each trial, two sets are visible: one contains a collection of blue circles, and the other includes a set of yellow circles.

Participants are asked to guess which set contains more. The dependent variable is percent accuracy, or the number of correct responses recorded as a function of the ratios across trials.

Performance accuracy is expected to be near chance when the ratio of circles are very similar—near 1:1—and improve as the ratio differences increase.

In other words, it’s easier to tell apart eight and four versus twelve and eight. In both cases, the subtractive difference is four, but the ratio differences vary, from 2:1 to 1.5:1.

To create the stimuli, generate circles of various sizes in blue and yellow sets. For each set, make sure that the numbers of blue and yellow circles are always different and represent the six ratios.

For each trial, code the program to divide the display to show one set from each color group on a gray background for 500 ms. Note that the color and circle size for the larger amount should be selected at random, and 20 trials with each ratio should be produced.

To begin the experiment, greet the participant in the lab and explain the instructions for the task. Once the participant understands the task rules, load the program.

When the circles disappear in each trial, have the participant press the ‘Y’ key if they think they saw more yellow dots, or the ‘B’ key if they think they saw more blue dots.

After each trial, provide immediate feedback via a tone to indicate whether the participant’s response was correct or incorrect.

To analyze the data, average the number of correct responses as a function of the ratio on each trial. Graph the mean accuracy percentage across ratio differences. Note that participants’ performances improved as the ratio differences increased.

Approximate number sense positively correlates with arithmetic abilities as measured by standardized tests, even though arithmetic is not about estimating.

In addition, even young children can apply number sense to identify when something is missing from a group of familiar objects.

You’ve just watched JoVE’s introduction to the Approximate Number Sense Test. Now you should have a good understanding of how to design and perform the experiment, as well as analyze results and apply the phenomenon of number estimation.

Thanks for watching!