Backward masking of conditioned stimuli: effects on differential and single-cue classical conditioning performance

Unconscious Learning. Conditioning to Subliminal Visual Stimuli

The role of consciousness in Pavlovian conditioning was examined in two experiments in which visually masked neutral words were used as the conditioned stimuli (CS) and an electric shock as the unconditioned stimulus (US). The inter-stimulus interval (ISI) was established individually. A detection threshold was used in Experiment 1 and an identification threshold in Experiment 2. The primary dependent variable was the skin conductance response (SCR). Results showed that the conditioned response (CR) was acquired by 58% of participants who perceived stimuli above the identification threshold, 50% of participants who perceived stimuli below the detection threshold, and 11% of participants who perceived stimuli below the identification threshold, but above the detection threshold. These results suggest that consciousness of the CS-US contingency is not a necessary condition for acquiring a CR of the autonomous nervous system (ANS).

Nonconscious control of autonomic responses: a role for Pavlovian conditioning?

This paper reviews data demonstrating nonconscious control of autonomic responses and emotional processes. After briefly having considered theoretical attempts to encompass such processes within Pavlovian conditioning frameworks, it goes on the examine theories and evidence for nonconscious control of emotional processes. The phenomena covered include affective discrimination, neurophysiological mechanisms in the control of conditioned emotional responses, and attentional biases in anxiety disorders. The main section of the paper examines evidence for nonconscious, automatic control of autonomic responses. Such control is demonstrated by data on skin conductance responses to nonattended stimuli, by skin conductance responses in prosopagnosic patients, and by skin conductance responses to masked conditioned stimuli. There are also some data suggesting that responses can be learned to nonconsciously presented in stimuli. In the discussion, it is argued that controlled processing may be dissociated from awareness. That is to say, stimuli may be processed at a controlled level without being accessible for conscious awareness. The relevance of these findings for Pavlovian conditioning is discussed.

Autonomic classical conditioning as a function of awareness of stimulus contingencies

Two groups of 32 college students were presented compound CSs (lights and tones presented simultaneously) during a classical conditioning paradigm. By means of a masking task and verbal instructions, a partially informed group was made aware of only the visual CS's contingency with the UCS, while a fully informed group was made aware of both the visual and auditory contingencies. Autonomic indices of conditioning (electrodermal responses, heart rate, and digital pulse volume) were later measured to the individual component CSs and to various compound CSs. It was found that: (1) the partially informed group exhibited conditioning exclusively to the visual CS+ and to compounds which included the visual CS+, while (2) the fully informed group exhibited conditioning to both visual and auditory CS+s. The results confirm the importance of awareness in human autonomic discrimination classical conditioning. It is suggested that human autonomic conditioning may be usefully conceptualized as an information processing task with the autonomic indices of conditioning reflecting central cognitive processes.