Anhedonia makes young people less likely to work for high rewards

Young people who experience a diminished ability to feel pleasure often struggle to adjust their physical exertion to obtain larger rewards. A recent experiment suggests this disconnect arises from specific cognitive difficulties in learning about both rewards and the physical costs required to get them. The study detailing these results recently appeared in the journal Psychological Medicine.

Depression is a leading cause of disability across the globe. A core feature of the condition is anhedonia. This symptom manifests as a general lack of interest and a blunted capacity to like or want things that most people find rewarding.

Psychologists often divide anhedonia into two distinct categories. Anticipatory anhedonia refers to a muted ability to look forward to future positive events. Consummatory anhedonia describes a reduced ability to enjoy a positive event in the physical moment it is happening.

Both types of anhedonia affect how individuals navigate their daily environments. We constantly make decisions based on past experiences, weighing the expected payoff against the required physical or mental cost.

Reward learning involves tracking which actions yield the biggest payoffs over time. Effort learning involves understanding the energy costs associated with those chosen actions.

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If a person cannot accurately learn which actions lead to the best outcomes, or if they struggle to estimate the energy needed for those actions, they might miss out on positive experiences. Past studies indicate that adults and adolescents with depression exhibit deficits in general reward learning.

Less is known about how depressed or anhedonic individuals learn about effort. Understanding the actual energy costs associated with a task is an essential part of daily decision making.

Angad Sahni, a researcher at the University of Reading, led a team to investigate these learning processes in young people. The researchers wanted to see if anhedonia alters the way people figure out how to maximize their payoffs and minimize their exertion.

They suspected that previous experiments might have been too challenging for participants. Earlier study designs required people to learn about rewards and effort at the exact same time.

In those older setups, individuals had to constantly switch their attention between assessing the value of a prize and gauging the physical toll of a task. The highly rewarding nature of the prizes often distracted participants from thinking about the effort involved.

To eliminate this distraction, Sahni and colleagues modified an existing computer-based learning task. They separated the experiment into distinct phases, allowing participants to focus solely on figuring out rewards in one phase and effort in another.

The experiment included 155 participants between the ages of 16 and 25. The volunteers experienced a wide spectrum of depressive symptoms, ranging from none to severe.

Before starting the computer task, the participants filled out a series of standardized questionnaires. These surveys assessed their current levels of depression and anxiety, as well as their specific experiences with both anticipatory and consummatory anhedonia.

The task itself was designed to evaluate behavioral learning through trial and error. The researchers chose pictures of puppies to represent high rewards and pictures of adult dogs to represent low rewards. Baby animals are consistently rated as highly pleasant, offering an immediate visual reward without requiring any monetary compensation.

Prior to the trials, the participants rated the animal pictures on a sliding scale from zero to 100. They indicated how much they liked looking at the puppies, how much they wanted to see them, and how much physical energy they were willing to expend for the chance to view them.

During the active learning blocks, the young adults faced a series of choices between two abstract shapes on a computer monitor. In the reward-focused block, selecting one shape yielded a puppy picture 75 percent of the time and an adult dog 25 percent of the time. The alternative shape offered the reverse odds.

The physical cost remained constant throughout the reward block. To reveal the picture, the participant had to rapidly press alternating keys on their keyboard 60 times to fill up a blue bar on the screen.

In the effort-focused block, the reward was always the high-value puppy picture, but the physical cost varied. One shape required high effort, or 60 rapid keystrokes, most of the time. The other shape required comparatively low effort, needing only 35 keystrokes.

The participants did not know the underlying odds when they started either phase. The instructions simply asked them to figure out which shapes led to the most puppies and which shapes required the least typing to fill the progress bar.

This setup allowed the researchers to measure learning accuracy. They tracked how often participants successfully chose the optimal shape in each block over the course of 50 total trials. They also recorded the speed of the alternating button presses as an objective measure of physical exertion.

To gain deeper insights into the learning process, the scientists applied computational models to the behavioral data. These mathematical models help explain the hidden cognitive steps that drive decision making.

One specific measurement they extracted was a temperature parameter. This metric captures the conceptual balance between behavioral exploration and exploitation.

A high temperature value suggests that an individual is making more random, exploratory choices. A low temperature value indicates that the person is exploiting their existing knowledge by consistently choosing the option they already know is best.

When analyzing the baseline ratings, the researchers found that higher levels of depression and consummatory anhedonia were correlated with lower overall liking of the puppy pictures. Participants with higher anticipatory anhedonia reported lower wanting, liking, and subjective willingness to work for the rewards.

During the active task, the participants generally pressed the alternating buttons faster for the high-reward puppies than for the low-reward adult dogs. This difference confirmed that the computer task successfully measured how people modulate their physical exertion based on a prize’s inherent value.

Participants with higher anticipatory anhedonia did not adjust their physical speed as much. They exerted a similar amount of effort regardless of whether they were working toward a puppy or an adult dog.

The data also revealed associations between symptom severity and learning accuracy. As general depression symptoms increased, the participants became less accurate at figuring out which shapes provided the highest rewards.

High consummatory anhedonia was linked to even broader difficulties. People who struggled to enjoy rewards in the moment showed decreased accuracy in both the reward and the effort blocks.

Results from the computational models provided a potential explanation for this poor performance. Higher consummatory anhedonia correlated with an increased temperature parameter during both phases of the experiment.

This suggests that these individuals chose options more randomly. Rather than exploiting the shapes that reliably offered low effort or high rewards, they continued to explore the less optimal shapes.

Over time, this pattern of underexploiting good opportunities means anhedonic individuals likely experience fewer rewards in daily life and expend more energy than necessary. Unnecessary physical exertion combined with smaller payoffs might then further diminish whatever small amount of pleasure they are able to feel.

While the findings provide a window into the mechanics of motivation, the current experiment has distinct limitations. The researchers acknowledged that the participant pool lacked broad demographic diversity.

Most of the participants were female, white, and highly educated university students. Only a small fraction of the volunteers had received a formal clinical diagnosis of depression from a medical professional.

The observed correlations were statistically modest, and some associations were not statistically significant after the researchers adjusted their calculations for multiple test comparisons. The team noted that an expanded participant pool would be required to verify the subtle relationships between these symptoms and abstract learning parameters.

Future investigations will need to recruit a more diverse array of participants, focusing particularly on patients with diagnosed clinical depression. Scientists also need to test how common psychiatric medications might alter a patient’s ability to learn about rewards and physical costs.

Understanding the specific learning deficits tied to anhedonia could eventually lead to new therapeutic strategies. By helping young people rebalance their exploration habits and accurately estimate physical costs, clinicians might help them comfortably reengage with rewarding experiences.

The study, “Anhedonia is associated with computational impairments in reward and effort learning in young people with depression symptoms,” was authored by Angad Sahni, Anna-Lena Frey, and Ciara McCabe.