Affective Bias Test (ABT)
The Affective Bias Test (ABT) is the gold-standard non-verbal assay for measuring how a depressed state alters learning and memory. It is fully translationally validated for both rodents and young children. [2, 4, 5]
Mechanism
The subject encounters two different neutral, non-verbal cues on different days (e.g., two different digging textures for a rodent; two different abstract coloured shapes on a screen for a child). Both cues yield the exact same positive reward (a treat or game token). Critically, one cue is learned while the subject is in a normal state, and the other is learned under a localized negative or stressed state. Later, the subject is given a free choice between the two cues (no reward present). [5, 6, 7]
Depression Marker
Depressed individuals exhibit a severe negative affective bias. Even though both options yield the exact same physical reward, they heavily avoid the cue associated with the period of negative mood. This demonstrates that depression actively distorts memory consolidation and value tracking. [2, 5, 6, 8, 9]
Drug Readout
In pre-clinical studies, depressed control groups heavily avoid the negatively-associated substrate. Effective antidepressants (ketamine, psilocybin) administered before the probe attenuate the negative memory bias, forcing a 50/50 baseline exploration or an increased preference for the previously avoided substrate.