The Impact of Expectations on Cognitive Performance: The Psychological Mechanisms of the Nocebo Effect
The expectations individuals develop before undertaking a task can influence their subsequent behaviour and how they evaluate their own performance. When people anticipate that they will struggle or fail, their attention, motivation, and approach to the task may change. In some circumstances, these changes can also affect actual performance outcomes.
One psychological concept that helps explain this phenomenon is the Nocebo Effect. It refers to the negative effects that expectations and previous experiences can have on an individual's symptoms, subjective experiences, and responses to particular situations. In recent years, researchers have also begun investigating how these mechanisms may be associated with attention and other cognitive processes, beyond their established relationship with physical symptoms.
The Nocebo Effect: Psychological and Physiological Foundations of Negative Expectations
The nocebo effect is generally understood as the counterpart of the placebo effect. While positive expectations and beliefs about the benefits of an intervention may contribute to favourable outcomes in placebo responses, negative expectations can produce undesirable reactions or intensify existing symptoms in nocebo responses.
The information individuals receive, their previous experiences, and their expectations about possible outcomes all play important roles in this process. For example, when someone anticipates that a particular activity will be difficult or unsuccessful, even relatively minor challenges encountered during that activity may be interpreted more negatively.Several mechanisms contribute to the development of nocebo responses. Negative expectations can increase anxiety, direct attention towards potential signs of failure, and encourage excessive monitoring of one's own performance. Consequently, expectations may influence not only how individuals think about an outcome but also how they approach the process of achieving it.
How Do Negative Expectations Affect Cognitive Resources?
Attention, working memory, and executive functions are essential cognitive resources that enable individuals to process information, organise tasks, and maintain goal-directed behaviour. These processes operate within limited cognitive resources. When individuals attempt to complete a task while simultaneously worrying about the possibility of failure, the distribution of their attention and mental resources may change.
For example, someone who doubts their abilities when faced with a challenging task may focus more on the possibility of making mistakes than on the actual requirements of the activity. As a result, some of the cognitive resources needed to monitor performance, process information, and make decisions may instead be occupied by anxiety-related thoughts.Anxiety can also influence attentional functioning. Excessive focus on potential threats and the possibility of failure may make it more difficult to select relevant information and maintain attention throughout a task.
Nevertheless, these mechanisms do not affect every cognitive function to the same extent. The relationship between negative expectations and cognitive performance may vary depending on the nature of the task, individual characteristics, and the surrounding context.
The Effects of Negative Suggestions on Cognitive Performance: Recent Experimental Evidence
A study by Barbon and colleagues, published in Psychological Research in 2026 under the title Beyond Expectations: Nocebo Suggestion Affects Cognitive Performance in Older Adults, provides interesting experimental evidence in this area.
The researchers investigated how positive and negative verbal information influenced cognitive performance among healthy older adults aged 65–80. Participants were divided into three groups. One group received neutral information, another was told that the intervention would improve their attention, and the third was informed that it could impair their cognitive performance.
The experiment involved an acoustic intervention with no actual active effect. Before and after the intervention, participants completed an Oddball Task, a test designed to measure attentional responses to auditory and visual stimuli.The findings indicated that participants who received negative suggestions demonstrated poorer performance on the cognitive task. More specifically, the improvement associated with repeated exposure to the auditory task, which was observed in the neutral and positive-information groups, was not observed in the group exposed to negative suggestions.
Although participants who received positive information were more likely to believe that the intervention would be beneficial, their objective performance did not show a significant advantage over the control group.Another notable finding was that the effect of negative suggestions on performance did not fully correspond to participants' explicitly reported negative expectations. This suggests that the influence of verbal information on behavioural outcomes cannot always be explained by consciously reported expectations alone.
However, the study included only individuals aged 65–80 and focused on specific attentional tasks. Its findings should therefore not be generalised to all age groups or other cognitive functions, such as memory and logical reasoning, without further evidence.
The Difference Between Subjective Experiences and Objective Performance
An important consideration in the study of the nocebo effect is the distinction between how individuals evaluate their own performance and how they actually perform a task.A person may feel inattentive, fatigued, or mentally less capable. However, these subjective experiences do not necessarily indicate a corresponding decline in objective cognitive performance. Similarly, individuals may perceive their performance as successful even when test results do not support that assessment.
An experimental study conducted by Blokland in 2023 illustrates this distinction. Research involving healthy young adults found that placebo and nocebo conditions influenced participants' perceptions of their attention, motivation, and performance. However, no significant placebo or nocebo effects were identified in objective measures of word learning, working memory, planning, or spatial memory.
A 2026 review by Braga and colleagues examining the effects of placebo and nocebo responses on cognitive functioning also emphasises that the available evidence remains limited. Differences in experimental tasks and research methodologies make it difficult to compare findings directly. In particular, the existing evidence on memory, attention, and working memory is not yet sufficient to support definitive conclusions.These findings highlight an important distinction: the influence of negative expectations on how individuals feel should not automatically be interpreted as an equivalent change in their actual cognitive performance.
The Role of Communication and Information in Shaping Expectations
Individuals evaluate information not only according to its content but also according to how it is presented. In educational, psychological assessment, and healthcare settings, the language used to communicate information can influence how people perceive their abilities and anticipate possible outcomes.For example, when individuals are told in advance that a task is extremely difficult and that most people fail to complete it successfully, they may approach the activity with greater anxiety. Conversely, clear explanations of task requirements and the purpose of an assessment can help reduce unnecessary psychological pressure.
The language used by professionals is therefore particularly important. This does not mean concealing information about potential risks or difficulties. Rather, the objective is to communicate information accurately, clearly, and in a balanced manner, without unnecessarily encouraging negative expectations about the outcome.
The Importance of Psychological Factors in Cognitive Assessment
Assessing cognitive performance requires more than simply counting correct and incorrect responses. Sustained attention, attitudes towards the task, anxiety levels, previous experiences, and the assessment environment can all be relevant when interpreting results.
In certain situations, negative expectations may make it more difficult for individuals to demonstrate their existing abilities. For this reason, cognitive assessments should be conducted under standardised conditions, with clear instructions and a psychologically neutral environment wherever possible.The objective is not to artificially improve performance by creating positive expectations. Instead, it is to minimise the potential influence of external suggestions and unnecessary psychological pressure, allowing an individual's actual cognitive functioning to be evaluated more accurately.
Understanding the Relationship Between Expectations and Cognitive Performance
The nocebo effect provides an important framework for understanding the role of expectations in psychological and behavioural processes. Current research suggests that negative suggestions can influence attention and task performance under certain conditions. However, these effects are not consistently observed across all cognitive functions, and positive expectations do not automatically lead to improved performance.
The broader significance of this research lies in highlighting the importance of considering not only the final outcome but also the psychological conditions under which it occurs. Cognitive performance depends not solely on knowledge and abilities but also on how individuals approach tasks, interact with information, and respond to their current psychological state.