the InMind blog

Negativity Bias: It’s Not All About Evolution!

• written by Lea Sperlich & Tabea Zorn

Editorial Assistants: Matilde Tassinari and Elena Benini

Note: An earlier version of this article has been published in the German version of In-Mind.

Negativity bias refers to the phenomenon that negative information carries more psychological weight than positive information. For instance, the sting of losing $10 is felt more intensely than the joy of gaining $10, and we are quicker to spot a threatening face in a crowd than a friendly one. Surprisingly, however, this effect doesn't seem to show up in evaluative conditioning (which is the change in the liking of a neutral stimulus due to its joint presentation with a positive or negative stimulus)—even when all the typical conditions for it are met. So, why doesn't the bias show up here? We take a closer look at the data to find out.

Fig. 1

Survival of the Most Anxious?

Negativity bias means that the "bad" outweighs the "good." We see this everywhere: we ruminate more over losses than we celebrate gains, remember negative events more vividly than positive ones, and identify a threat in a group of people much faster than a smile [1].
From an evolutionary psychology perspective, this makes perfect sense. It’s about survival: the ancestor who ignored a saber-toothed tiger in the brush didn’t live long enough to pass on their genes. Meanwhile, missing out on a few edible berries was a minor setback – they could always find more later.
Based on this evolutionary view, we would expect a negativity bias to appear whenever both positive and negative information are present – as is the case with Evaluative Conditioning.

The Curious Case of Evaluative Conditioning

In evaluative conditioning, neutral images (like geometric shapes) are paired with either positive images (e.g., puppies) or negative images (e.g., spiders). These pairings change how we feel about the originally neutral shapes [2]. If a triangle is paired with a kitten, it starts to feel "good"; if a square is paired with a snake, it starts to feel "bad."
However, data from various studies show that even though both "good" and "bad" information is present, evaluative conditioning shows no negativity bias [3]. This means the shapes paired with negative images weren't rated more extremely than those paired with positive ones. In other words, the negative info didn't hit any harder than the positive info. Why?

Ecology over Evolution?

One explanation might be the setup of the experiments themselves. In many studies, researchers present an equal amount of positive and negative information. If there are four shapes paired with four positive animals, there are usually four shapes paired with four negative ones.
But that’s not how the real world works. In nature and society, negative information is typically rarer than positive information. Think about your daily life: we usually have far more positive social interactions than negative ones. Even our language reflects this –analyses show that negative words are used much less frequently than positive ones (e.g., [4]). And rarity has its perks: unique or infrequent information sticks in our memory much better (the von Restorff effect, [5]).

Fig. 2. von Restorff effect: rare (distinctive) stimuli are more likely to be remembered.
Could it be that the " power" of negative information comes simply from the fact that it is rare? Is it a matter of ecology rather than evolution?

The Experiment: Reversing the Ecology

To test this, we manipulated the distribution of information. If negative information is more impactful because it is rare, then a negativity bias should appear when negative info is scarce. Conversely, if positive information is rare, we should see a positivity bias [3].
Participants were split into two groups (Experiments 2 & 3):
1.    Group A (rare negative): Four neutral shapes were paired with positive images, and only one shape was paired with a negative image.
2.    Group B (rare positive): Four neutral shapes were paired with negative images, and only one shape was paired with a positive image.
The results matched the hypothesis perfectly. The single negative image in Group A had a much stronger impact than the four negative images in Group B ( negativity bias). Simultaneously, the single positive image in Group B was more influential than the four positive images in Group A ( positivity bias).

In a Nutshell

In evaluative conditioning, negative information only seems to have a stronger pull when it is rare. While this study didn't rule out an evolutionary "head start" for negative stimuli, it proves that evolution isn't the whole story.
As is often the case in psychology, it’s rarely just one factor. Neither ecology nor evolution can explain these biases on their own. The takeaway? Context and frequency matter. Rare things hit harder – whether they’re positive or negative.

Bibliography

[1] R. F. Baumeister, E. Bratslavsky, C. Finkenauer, and K. D. Vohs, "Bad is stronger than good," Rev. Gen. Psychol., vol. 5, no. 4, pp. 323–370, 2001, doi: 10.1037/1089-2680.5.4.323.
[2] J. De Houwer, D. Barnes-Holmes, and A. Moors, "What is learning? On the nature and merits of a functional definition of learning," Psychon. Bull. Rev., vol. 20, pp. 631–642, 2013, doi: 10.3758/s13423-013-0386-3.
[3] L. M. Sperlich and C. Unkelbach, "Why is there no negativity bias in evaluative conditioning? A cognitive-ecological answer," J. Pers. Soc. Psychol., vol. 128, no. 1, pp. 19–37, 2025, doi: 10.1037/pspa0000431.
[4] C. Unkelbach, A. Koch, and H. Alves, "The evaluative information ecology: On the frequency and diversity of 'good' and 'bad'," Eur. Rev. Soc. Psychol., vol. 30, no. 1, pp. 216–270, 2019, doi: 10.1080/10463283.2019.1688474.
[5] H. Von Restorff, "Über die Wirkung von Bereichsbildungen im Spurenfeld," Psychol. Forsch., vol. 18, pp. 299–342, 1933, doi: 10.1007/BF02409636.

Figure Sources

Figure 1: Pixabay
Figure 2: Self-produced