The Cocktail party effect is the phenomenon in which one can focus attention on a particular stimulus among others, such as a single conversation in a noisy room. Early experiments by Cherry and Moray used shadowing tasks that presented different messages into different ears of each participant. People were able to easily focus on one message while rejecting and gathering very little information from the other (Cherry, 1953; Moray, 1959). This work also paved the way for several theories of selective attention such as Broadbent’s filter model (a ‘filter’ blocks out unattended information; Broadbent, 1954) and Treisman’s attenuation theory of attention (unattended information is not completely blocked out, but processed at a subconscious level and words of semantic importance can be drawn from the unattended information; Treisman, 1969).
See:
Cherry, E.C. (1953). Some experiments on the recognition of speech with one and two ears. J. acoust. Soc. Amer. 25, 975-979.
Moray, Neville (1959). Attention in dichotic listening: Affective cues and the influence of instructions. Quarterly Journal of Experimental Psychology. 11, 56-60.
Broadbent, D.E. (1954). The role of auditory localization in attention and memory span. Journal of Experimental Psych. 47, 191-196.
Treisman, A. M. (1969). Strategies and models of selective attention. Psychological Review. 76, 282-299.