A human perception test has been conducted to determine the correlation between observer response and the number of spatial cues without thermal attributes, thermal cues, and total cues in an image. The experiment used the NVESD 12 target LWIR tracked vehicle image set. Various levels of Gaussian blur were applied to twelve aspects of the twelve targets in order to reduce both the number of resolvable cycles and the number of observable thermal and spatial cues. The author then counted every observable thermal and spatial cue in each of the processed images. A thermal cue was defined as either a hot spot or a cool spot. Typically, hot spots are produced by a vehicle's engine or exhaust. Cool spots are features such as air intakes and trim vanes. Spatial cues included characteristics such as barrel length, turret size, and number of wheels. The results of a 12 alternative forced choice identification perception test were analyzed to determine the correlation coefficients between probability of identification and the number of thermal, spatial, and total cues. The results show that the number of spatial cues in an image was strongly correlated with observer performance.