Biological swimmers such as E. coli bacteria or spermatozoa exhibit chemotaxis: Inside gradients of nutrients or chemical messengers, these organisms migrate up-gradient toward the source. Chemical sensing, information processing and active reorientation are required to gain the evolutionary advantage involved in chemotactical behavior. On the contrary, active Brownian particles (ABPs), synthetic swimmers which are driven by catalytic reactions with additives to the solvent, are well known to exhibit anti-chemotaxis: Inside activity gradients, their stationary density distribution is at its maximum in regions of low activity. We demonstrate how in non-stationary setups a transient chemotaxis, called 'pseudochemotaxis', emerges, during which these ABPs initially explore regions of high activity. Moreover, we show in theory and simulation that complexes of loosely bound ABPs, or dimers of an ABP and a (heavier) passive particle, can develop a true chemotaxis, i.e. migrate into regions of high activity. Since this phenomenon does neither require chemical sensing nor active orientation, it may serve as a tool for primitive microorganisms at the lowest stage of evolution to locate their food.