Handedness refers to the lateral preference an individual exhibits when performing motor tasks. While most people show a clear preference for either the right or the left hand, human laterality exists on a spectrum, with some individuals demonstrating inconsistent or mixed preferences. A mixed handedness test is a systematic tool designed to quantify this spectrum of manual preference, distinguishing between strong, moderate, and inconsistent hand use across various activities. The test helps to accurately map an individual’s unique pattern of hand dominance for clinical, research, or educational purposes.
Defining Mixed Handedness and Related Terms
Mixed handedness, often referred to as cross-dominance or mixed dominance, describes a pattern where an individual uses different hands for different tasks. For instance, a person might write with their right hand but consistently prefer to throw a ball or use a spoon with their left hand. This inconsistency is the defining characteristic of mixed handedness, which is present in roughly 1% of the population, similar to the prevalence of left-handedness. This pattern should not be confused with true ambidexterity, which is the rare ability to perform any given task with equal skill and precision using either hand.
Crossed laterality is a broader term that extends beyond the hands to include the eyes, feet, and ears. A person displays crossed laterality when the dominant hand and, for example, the dominant eye are on opposite sides of the body. A test for mixed handedness seeks to precisely measure the degree of inconsistency in hand use rather than simply identifying a person as non-right-handed.
Standardized Assessment Tools
Formal assessment of mixed handedness relies on standardized, quantifiable tools designed to capture the nuance of hand preference, such as the widely used Edinburgh Handedness Inventory (EHI). The EHI is a questionnaire that asks individuals to report their preferred hand for a series of ten common unimanual tasks like writing, drawing, throwing, and using a toothbrush. Responses involve a scale that indicates the strength of preference, often using a point system for “strong preference” versus “weak preference.”
The results from these preference scores are used to calculate a Laterality Quotient (LQ), which is a numerical score ranging from -100 (absolute left preference) to +100 (absolute right preference). Scores close to the center of this range indicate mixed or indeterminate handedness.
Common Observational Tasks
In addition to self-report inventories, mixed handedness can be assessed through the direct observation of performance on various motor tasks, which is useful for young children or in non-clinical settings. These tasks are typically divided into those requiring fine motor skills (e.g., cutting with scissors, turning a key in a lock, or threading a needle) and those demanding gross motor skills (e.g., throwing a ball, sweeping with a broom, or striking a match).
A person with mixed handedness often uses different hands for each category. Observing an individual consistently switch hands depending on the task type—using the right hand for writing but the left hand for throwing—is a clear indicator. Specialized observational assessments, like the WatHand Cabinet Test, require the person to perform a variety of everyday actions to systematically record the preferred hand for each one.
Understanding the Implications
Identifying mixed handedness provides context regarding an individual’s brain organization, which is less lateralized than in strongly-handed people. Research suggests that this pattern of inconsistent manual preference may be associated with certain developmental or cognitive variations. Studies have noted correlations between mixed handedness and an elevated risk for certain language and scholastic challenges, including some symptoms of Attention Deficit/Hyperactivity Disorder (ADHD), particularly in childhood populations.
Conversely, evidence indicates that this bilateral organization may offer advantages, such as improved performance in memory tasks or in sports requiring active body movements and rapid responses from both sides of the body. The meaning of a mixed handedness test result is simply to describe a variation in manual coordination, and it rarely signifies a disorder. The finding suggests that individuals may benefit from flexible accommodation in environments and tool use, rather than being forced into a single dominant hand use pattern.